2003 Asymetry EEG Emotion

State and Trait Frontal EEG Asymmetry in Emotion p.1 Chapter appearing in: K Hugdahl & R.J. Davidson (Eds), The Asymmetrical Brain. Cambridge, MIT Press, 2003 The State and Trait Nature of Frontal EEG Asymmetry in Emotion James A. Coan John J.B. Allen University of Arizona 29 June 2003 Abbreviated Title: STATE AND TRAIT FRONTAL EEG ASYMMETRY IN EMOTION Word Count: 9,770 (excluding references and tables) Figure Count: 2 Word Equivalents: 10,370 Corresponding Author Information: James A. Coan Department of Psychology University of Arizona, POBox 210068 Tucson, AZ, 85721-0068 Email: [email protected] Phone: (520) 621-7086 FAX: (425) 940-5948 Acknowledgements This work was supported, in part, by a Young Investigator award from NARSAD (John Allen) and a Graduate Research Fellowship from the National Science Foundation (James Coan). State and Trait Frontal EEG Asymmetry in Emotion p. 2 Table of Contents Introduction......................................................................................................................... 3 Current Conceptualizations of Asymmetries in Cortical Activation............................... 3 The Nature of Frontal EEG Asymmetry......................................................................... 6 About the Tables.............................................................................................................. 8 Frontal EEG Activation Asymmetry as a Trait Measure.................................................... 9 Trait Frontal EEG Asymmetry and Other Trait-like Measures..................................... 11 Trait Frontal EEG Asymmetry and Measures of Psychopathology .............................. 14 Trait Frontal Asymmetry as a Predictor of State-dependent Changes .......................... 19 Frontal EEG Activation Asymmetry as a State Measure.................................................. 22 The Relationship Between Trait and State Frontal EEG Asymmetry .............................. 27 Conceptual Models for Understanding Trait-State Asymmetry Relationships ............. 29 Data Bearing on the Trait-State Relationship................................................................ 31 Conclusion ........................................................................................................................ 34 Footnotes........................................................................................................................... 39 References......................................................................................................................... 41 State and Trait Frontal EEG Asymmetry in Emotion p. 3 Introduction Over 60 studies have now been published examining the relationship between asymmetrical electroencephalographic (EEG) activity over the frontal cortex and emotion or emotion-related constructs. Two research approaches typify this literature. The first involves correlating resting EEG activity with trait-like phenomena such as temperament or psychopathology, or with state fluctuations in emotion. The second involves correlating state fluctuations in frontal EEG asymmetry with changes in emotional or motivational state. This paper reviews this literature highlighting the state or trait nature of these studies and provides a framework for conceptualizing state- and trait- related EEG asymmetry as it relates to emotion and emotion-related processes. Current Conceptualizations of Asymmetries in Cortical Activation Frontal EEG asymmetries have most frequently been associated with motivational and affective traits and states, most notably fundamental approach and withdrawal orientations and actions (Davidson, 1993). According to the approach/withdrawal model of frontal EEG asymmetry, relatively greater left frontal activity should generally result in either an approach orientation or an approach-oriented action (Davidson, 1993). In contrast, relatively greater right frontal activation should generally result in either a withdrawal orientation or a withdrawal-oriented action (Davidson, 1993). This primarily motivational model of frontal EEG asymmetry overlaps substantially (Davidson, 1992) with more affective models, such as the valence model. According to the valence model, relatively greater left frontal activation is associated with positively-valenced emotions, while relatively greater right frontal activation is associated with negatively valenced emotions (Davidson, 1992). In recent years, evidence associating relatively greater left From this perspective. Weidemann. 1998. Davidson & Tomarken. 1993. a smaller number of studies have examined state- dependent changes in EEG asymmetry. Allen & Harmon- Jones. frontal EEG asymmetry has been associated with both trait-like and state-dependent processes. Harmon-Jones & Allen. as anger is a negatively valenced emotion characterized by relative left frontal activation. as well as with general behavioral activation tendencies independent of valence (Harmon-Jones & Allen. Henriques & Davidson. Ekman & Davidson. The vast majority of work in this area focuses on frontal activation asymmetry as a trait measure. Although trait-like frontal EEG asymmetry has been associated with state- dependent affective responses. 1997). Within both the approach/withdrawal and valence models. such as depression and anxiety (Allen. Depue. Iacono. 1991. 1999). Lutzenberger. suggest that the approach/withdrawal model is the most universal model of frontal EEG asymmetry. Wheeler. trait levels of frontal EEG asymmetry have been used to predict the magnitude of state-dependent fluctuations in affective reports (Tomarken. 1998). 1997. 1990. in press. 1997. Harmon-Jones & Allen. Pauli. behavioral activation or aggression (Harmon-Jones & Allen. & Arbisi. Sutton & Davidson. The valence model is. To a lesser degree. trait frontal asymmetries have most commonly been associated with other traits. 1993). obviously. associating fluctuations in frontal EEG asymmetries with concomitant fluctuations in affective states (Coan. Schmidt. unable to accommodate these recent anger findings. 1993). By contrast. 2000a. Dengier. 1999). State and Trait Frontal EEG Asymmetry in Emotion p. 4 frontal activation with trait and state anger (Harmon-Jones. little is known about . such as sociability. usually in the form of self-report. Birbauer & Buchkremer. or various forms of psychopathology. Davidson & Henriques. 2000) were found that involved any investigation of the relationship between trait levels and state-related changes in frontal EEG asymmetry. For example. These traits. Luerken & Bartussek. serve as diatheses that increase risk for psychopathology. In fact. in press.. and that predict other traits and behaviors.that is. State oriented inquiries such as this would argue that state- .. no published studies. trait frontal EEG asymmetry will refer to asymmetries that are consistent intra-individually across time. State frontal EEG asymmetries. Kline. 1998a. 2000. et al. or asymmetries examined in research studies that make this assumption even though asymmetries may not be measured on multiple occasions. it is further argued (and demonstrated with ample research . usually in the form of a verbal report (Davidson. 2000a. Ekman and Davidson (1993) found that smiles that included the activation of the orbicularis pars lateralis muscle (the Duchenne smile) resulted in an increase in left frontal activation relative to ("unfelt") smiles that did not include this movement. 1993). 1998a). Haggemann. 1961). that individuals possess certain frontal EEG asymmetries as relatively stable traits. Harmon-Jones. State and Trait Frontal EEG Asymmetry in Emotion p. Ekman and Davidson. 1999) and a recent symposium (Coan & Allen. 2000b.see for example Davidson. Wheeler. et al. 1993). Examples of this would include person-independent differences in frontal EEG asymmetry resulting from different voluntary emotional facial expressions (Coan. may be thought of as those that are responsive to specific environmental conditions (Cattell & Scheier. Naumann. 5 how trait and state frontal EEG asymmetries are related. and only the published abstracts of one author (Hagemann. by contrast. For the purposes of this chapter. Research of this type would argue that frontal EEG asymmetries represent properties of the individuals possessing them . These traits modulate state measures such as emotional reactivity. Alpha. The assumption underlying research examining frontal EEG asymmetries. to absolve the reader of additional cognitive operations to interpret the findings. therefore. properties of Duchenne and unfelt smiles). Davidson. & Henriques. Thus trait studies of EEG asymmetry adopt an individual differences approach. indeed. therefore. . many reports will discuss correlations between depression and relatively greater left frontal alpha. Chapman. The first concerns the dependent measure: alpha activity. several issues relevant to the interpretation of frontal EEG asymmetry (or. leaving the reader to remember that the sign attributed to the correlation will have to be reversed in order to correspond to relatively greater left frontal activation. any hemispheric asymmetry in scalp recorded EEG) are worth highlighting. and assume that such state-EEG relationships generalize across individuals. In the present chapter. typically in the 8-13 Hz range. asymmetries will be reported in terms of activation. however. State and Trait Frontal EEG Asymmetry in Emotion p. while state studies of frontal EEG asymmetry assume a normative approach. is generally thought to be inversely related to brain activation. 1990). is that an asymmetry in alpha represents an asymmetry in the opposite direction in terms of activation of cortical regions1. is extracted at any given site. The Nature of Frontal EEG Asymmetry Before reviewing the literature on frontal EEG asymmetry and emotion.g. For example. 6 related changes in frontal EEG asymmetries represent properties of the states per se (in the case of the example. as blocking of or decreases in alpha are seen when underlying cortical systems engage in active processing (e. Chapman. This alpha/activation inverse can make reading the literature challenging. State and Trait Frontal EEG Asymmetry in Emotion p. 7 A second set of issues concerns the problem of what actually produces the asymmetry effects. Many investigators, for example, report a hemispheric difference score between homologous sites. This common practice usually involves subtracting the natural log (ln) of the right hemisphere alpha from that of the left hemisphere (ln[Right] – ln[Left]). The resultant difference score provides a unidimensional scale, wherein higher scores indicate relatively greater left frontal activation and lower scores indicate relatively greater right frontal activation (keeping in mind the putative inverse relationship between alpha and activation). The difficulty with the use of such a difference2 metric is in ascertaining whether one, the other, or both of the hemispheres is involved in producing the difference. Fortunately, many investigators compare left and right hemispheric alpha power in addition to or instead of computing the difference score. Nonetheless, regardless of whether results are expressed as difference scores or constituent scores, it can be challenging when reading the literature to determine what is actually changing relative to what. In depression studies, for example, one will variously encounter "greater right frontal activation" (e.g., Shaffer, Davidson & Saron, 1983; p. 759) and "lower left frontal activation" (e.g., Gotlib, Ranganathad & Rosenfeld, 1998; p. 449). It is not always clear whether a single hemisphere has a particular stake in certain effects, or whether the critical determinant is the relative difference between hemispheres, however achieved. Related to the issue of whether left or right hemisphere changes are producing effects is the observation that the difference between hemispheres is relatively small compared to the overall magnitude of activity in each hemisphere. The correlation between homologous sites (e.g. F3 and F4, or F7 and F8) is substantial, ranging from .95 State and Trait Frontal EEG Asymmetry in Emotion p. 8 to .99 (e.g., Tomarken, Davidson, Wheeler and Kinney, 1992). The asymmetry, then, accounts for little variance in overall EEG activity, but captures important variance related to motivation and emotion. In fact, when the impact of the homologous lead is statistically controlled prior to calculating the difference score (cf. Fox, Rubin, Calkins, Marshall, Coplan, Porges, Long & Shannon, 1995), the relationship of asymmetry to criterion measures appears to be enhanced. About the Tables The tables included in the forthcoming pages summarize the literature on EEG hemispheric asymmetries in emotion, confined to frontal regions only. They are intended to provide certain details of general interest as well as those of interest to the study of EEG asymmetry in particular. Of general interest are various sample characteristics, along with a tabular summary of the results. Additionally, information has been provided that is of particular interest to investigators who may intend to conduct studies of this nature. For example, as one peruses any of the tables, one will immediately recognize that most reports include only right-handed participants. This is generally attributed to evidence (e.g., Bryden, 1982) that hemispheric lateralization may be partially a function of handedness. These tables include the specification of handedness in the attempt to identify studies where handedness is either not addressed or mixed (inter-individually, not intra-individually). (To our knowledge, there are no published studies utilizing a left handed only sample.) Also, it is increasingly apparent that different references (e.g., vertex, linked mastoids, left ear, etc…) each contribute unique sources of variance and error to the analysis of asymmetries in scalp recorded EEG (Henriques & Davidson, 1991; Reid, Duke & Allen, 1998). Because no reference has thus far unequivocally State and Trait Frontal EEG Asymmetry in Emotion p. 9 emerged as preferred, a column for the reference scheme used in each study has been included, with the hope that this may prove useful. Frontal EEG Activation Asymmetry as a Trait Measure In his classic article, Allport (1966) proposed 8 properties of traits. First, he asserted that traits must have more than nominal existence. Second, he argued that traits must be more generalized than habits. Third, he proposed that traits must be determinative of behavior. The remaining properties read like a checklist: fourth, traits should be established empirically; fifth, traits should be only relatively independent of other traits; sixth, traits should not be synonymous with moral or social judgments, seventh, traits can be studied idiomorphically or in terms of their distributions in the general population; and eighth, acts or habits that are inconsistent with a given trait do not necessarily constitute evidence of the nonexistence of that trait (Allport, 1966). His subsequent discussion, like so many discussions of personality traits, centers on how traits are to be measured, and, to a lesser extent, whether traits can ever be considered "real" or only as hypothetical constructs. As a trait measure, frontal EEG asymmetry appears to satisfy each of Allport’s criteria. With regard to measurement, the primary issue in determining the trait-like qualities of frontal EEG asymmetry involves establishing the measure's stability. Because the asymmetry can be measured more or less directly, it is less vulnerable (though by no means invulnerable) to the myriad measurement errors surrounding other trait-like constructs. Addressing the issue of stability, Tomarken, Davidson, Wheeler & Kinney (1992) assessed the psychometric properties of trait-like frontal EEG asymmetries and were able to determine that frontal EEG asymmetry showed high internal consistency (Cronbach's alphas ranging from .81 Apart from its psychometric properties. Bem & Allen.. Wheeler et al. 60% of the variance of the asymmetry measures was due to individual differences of a temporally stable latent trait.44 to . p < . crying behavior in response to maternal separation (Davidson & Fox. Harmon-Jones & Allen. and 40% of the variance of the asymmetry scores was due to occasion-specific fluctuations. who found that across four different measurement occasions. 1997) and risk for psychopathology (e. Baeudecel. Heilemann & Kayser. and predicted basal natural killer cell immune function (Davidson. 1996) and. 1974). 1999. some studies have specifically examined subjects who show the greatest cross-session consistency (e. 10 to . In another study. Dawson. et al. Similar figures come from Hagemann (2000)..g. Hitt. Trait like frontal EEG asymmetry has. 1990). Field. characterized the infants of depressed mothers (e. Davalos and Pickens (1997) found that frontal EEG asymmetry recorded at 3 months of age was highly correlated with the same asymmetry at 3 yrs (r = ..g. 1989). Henriques & Davidson. trait frontal EEG asymmetry has been associated with other relatively stable traits (e. Trait frontal EEG asymmetry has been used to predict the intensity of emotion in response to emotionally-evocative films (Wheeler.. it has predicted internalizing and externalizing difficulties (Fox. 1993). . Nessler. and has been found to change little despite changes in clinical status in depression (Allen et al. 1993...71 across 3 weeks). Rubin. in infants.01). Frey. reasoning that the strongest relationships to other traits should be shown by those who are consistent on the measure of trait EEG asymmetry (cf. 1993). On the other hand. In children.g.90) and acceptable test-retest stability (intra-class correlations ranging from . & Allen. Brocke. Kitt & Coplan. in part. Calkins. Urry. although see Debener. Coe. 2000). Schmidt. 1999).g. Panagiotides. Jones.66. Dolski & Donzella. State and Trait Frontal EEG Asymmetry in Emotion p. 1987) behavioral inhibition and activation systems (BIS and BAS. specifically: trait frontal EEG and it's relationship to other trait-like measures. categorizing the literature on trait-like asymmetry into manageable sub-sections. Several researchers have identified a . 1997). a number of particularly influential and interesting studies should be highlighted. which are intended to measure Gray's (1972. and guiding organisms toward attaining a desirable stimulus. the BIS initially inhibits action and subsequently guides behavior toward removing or avoiding an undesirable stimulus. and trait frontal EEG asymmetry as a predictor of state-dependent changes in emotion. ------------------------------------------------------------------- Insert table 1 about here ------------------------------------------------------------------- Frontal EEG asymmetry is thought to relate to various personality traits. A clear example of this can be found with Carver and White's (1994) BIS/BAS scales. responding to incentives. Following from the approach/withdrawal model of asymmetry. trait patterns of propensities to approach or engage with the environment or to withdraw from the environment should be associated with this EEG measure. State and Trait Frontal EEG Asymmetry in Emotion p. it will be useful to review the entire literature in some detail. The BAS essentially functions in the opposite manner. Given the very wide range of relationships that trait frontal EEG asymmetry appears to have. Trait Frontal EEG Asymmetry and Other Trait-like Measures A comprehensive tabular summary of this literature can be found in Table 1. respectively) as traits. 11 Osterling & Hessl. trait frontal EEG asymmetry and psychopathology. According to Gray. Although no attempt will be made to review every report within the body of this paper. 1997). with other withdrawal variance distributed across Gray's (1972. Harmon-Jones and Allen. and even the BAS. 1997). Harmon-Jones & Allen. Relatively greater right frontal activation was associated with higher BIS scores (Sutton & Davidson. however. Sutton & Davidson. 1997). respectively. but not so robust for BIS. suggesting that the theoretical association between withdrawal motivations and the BIS is more complex than that between approach motivations and the BAS (Coan & Allen. neither were able to detect an association between relative right frontal activation and BIS scores. it is primarily thought to motivate behavioral inhibition in response to an aversive stimulus. 2000a. Thus. The BIS. this is suggested by the fact that. theoretically. 12 relationship between these systems and frontal EEG asymmetry (Coan & Allen. 1997. Work by Harmon-Jones and Allen (1997) and Coan and Allen (2000a). In part. away from a stimulus. Sutton and Davidson (1997) proposed that the BIS and BAS should map closely onto withdrawal and approach tendencies. State and Trait Frontal EEG Asymmetry in Emotion p. may only tap one step in a chain of events that may lead to withdrawal behaviors. or tendencies toward movement. 2000a. For example. Davidson's (1998a) withdrawal construct is potentially more heterogeneous than that of the BIS. Davidson’s withdrawal construct references movement. whereas Davidson’s approach and Carver and White’s BAS constructs share more in common. suggest that the relationship is robust for BAS. and indeed found that relatively greater left frontal activation was associated with both higher BAS scores and greater BAS-BIS differences scores. on the other hand. While both of these reports found associations between relative left frontal activation and higher BAS scores. variance due to withdrawal orientations or actions may overlap only slightly with the BIS. 1987) Fight/Flight System (FFS). which is to a lesser extent thought to motivate individuals to avoid . In both of these studies. That is. who . 1990) showed higher levels of left frontal activation than low-defensive subjects. 1994). et al. 1999. Tomarken and Davidson (1994) demonstrated a relationship between defensive coping style and frontal EEG asymmetry (see also Kline. Fox.. 1995). and scored lower on measures of social competency (Fox. but a more dramatic demonstration of this independence is found in the work of Harmon-Jones and Allen (1998) and more recently Harmon-Jones (2000a). In their analysis. (1995). 13 punishing situations. who are presumably motivated to avoid negative affect (Schwartz. some individuals are motivated to avoid negative affect associated with certain situations. Analogously. children with greater left frontal activation were both more sociable and more socially competent. In their analysis. children with greater right frontal activation were generally more inhibited socially. State and Trait Frontal EEG Asymmetry in Emotion p. high-defensive subjects. individuals who score more highly on measures of trait anger show relatively greater left frontal activation at rest. These results fit well with those of Schmidt and colleagues (Schmidt. found evidence for this in children. Allen. Trait approach and withdrawal dispositions indexed by frontal EEG asymmetry are likely to hold consequences for traits associated with social behavior. 1998 for a replication with women but not men). Schmidt & Fox. left frontal activation was associated with trait anger. The relationship between frontal EEG asymmetry and the BAS has highlighted the relative independence of the approach/withdrawal and valence continuums. a negatively-valenced but approach- related emotion. Harmon-Jones (2000a) has found that trait anger is associated with both an increase in left frontal activity and a decrease in right frontal activity. et al. & Schwartz. Additionally. but when in remission as well. Schmidt (1999) also found that shy individuals who nevertheless scored high on measures of sociability possessed greater left frontal activation than other shy individuals with low sociability scores (Schmidt. with higher CRH levels associated with higher levels of stress. In rhesus monkeys. Shelton & Davidson. Trait Frontal EEG Asymmetry and Psychopathology Consistent with its relationships to other personality traits. Interestingly. State and Trait Frontal EEG Asymmetry in Emotion p. Kalin. Schmidt and Fox (1994) found that individuals scoring low on measures of sociability evidenced relatively greater right frontal activation. 1999). 14 investigated the relationship between EEG asymmetry and similar traits in adults. while sociability was positively related to relatively greater left frontal activation (Schmidt. CRH has itself been identified as a mediator of stress responses. anxiety and depression. and may tap a diathesis towards depression in particular. et al. they have found a positive relationship between extreme right frontal activation asymmetry at rest and high cerebrospinal fluid concentrations of corticotrophin-releasing hormone (CRH.. et al. (De Souza. in that relative right frontal activation characterizes depressed individuals not only when depressed. 2000) have begun to investigate other physiological traits that may underlie processes related to those reviewed above. 1999). 1995. 2000). frontal EEG asymmetry appears to be related to emotion-related psychopathology. 2000). Kalin. . In recent work. as well as responses to fear.. Schmidt (1999) subsequently determined that frontal EEG asymmetry was related to measures of sociability and shyness. Kalin and colleagues (Kalin. Shyness was positively associated with relatively greater right frontal activation. Debener. This general relationship has been replicated and extended (e. 1998. but also euthymic individuals who have suffered previous bouts of depression (Gotlib et al. State and Trait Frontal EEG Asymmetry in Emotion p. Reid. et al. using the Beck Depression Inventory (BDI) as their measure of depression. included not only depressed individuals. 1998. et al. found that high scorers on the BDI showed relatively greater right frontal activation. In the first report in this domain. 1991).. and suggested that frontal EEG asymmetry may tap one of several possible risk-trajectories associated with the disorder. . Reid et al (1998) highlighted the heterogeneous nature of depression. Gotlib. or interacted with.and depression (e. 1991.. Rosenfeld & Baehr. 1993. et al. 1993). These results have. (1998). Davidson & Saron. did not find frontal EEG asymmetry to discriminate depressed from non-depressed subjects.. 15 ------------------------------------------------------------------- Insert table 2 about here ------------------------------------------------------------------- Links have been established between lower left frontal activation . 1998. Henriques & Davidson... Henriques & Davidson. (1983). and subsequent studies found the same relationship among clinically diagnosed subjects (Allen et al. Henriques & Davidson. Allen et al. 1993. 2000).or relatively more right frontal activation . and that as yet unidentified aspects of the experimental environment may have masked. 1990. For example.. 1998). (1998) emphasized the fact that traits will interact with the particular experimental environment..g. in some studies. Additionally. in two separate and reasonably large samples. Schaffer. Schaffer. et al. et al. Reid et al. but not without some conflicting results (Reid. 1990).g.. asymmetries that may have existed prior to measurement. 1983) and seasonal depression (Allen et al. Baehr. and identical differences in their respective infants. Panagiotides. Tellegen & Iacono.. Hessl & Osterling. 1999). it would be difficult to tease apart the influence of genes versus environment in producing relatively greater right/lower left activation in the children of depressed mothers. and a conference report suggests that frontal EEG asymmetry shows greater similarity in monozygytic twins than dizygotic twins (MacDhomhail. Further. 1995). Yamada & Rinaldi. In other studies. reporting more right frontal activation (not less left frontal activation) in depressed versus non-depressed mothers. Pickens & Nawrocki. Self. Dawson. Field et al. 16 Further evidence of an association between frontal EEG asymmetry and depression can be found in studies finding relative right frontal activation in infants of depressed mothers (e. Allen. Frey. Fox. . but they also address. On the other hand. and that infants of depressed mothers show evidence of left hypoactivation while at rest. Hessl. Field. Frey. 1997). et al. left frontal activity discriminated infants whose mothers were diagnosed with major depression from those whose mothers were considered to be sub-threshold. or hold the potential for addressing. 1999). Dawson. 1999.g. (1997) discovered that infants of depressed mothers showed less left frontal activity than those of non-depressed mothers (Dawson. Dawson and colleagues have demonstrated that infants of depressed mothers who show concomitant left frontal hypoactivation are less affectionate with their mothers (Dawson. Panagiotides. et al. Yamada.. Because the infants studied in these reports were being raised by their biological mothers. and while interacting with familiar strangers (Dawson. State and Trait Frontal EEG Asymmetry in Emotion p. et al. Katsanis. & Iacono. These infant studies are important in their own right. while interacting with their mothers. the question of how trait frontal EEG asymmetry patterns originate. EEG spectra are modestly heritable (Lykken. 1982). (1995) have independently achieved similar effects. suggesting some trait-like stability in the face of changes that may or may not track the severity of symptomatology. State and Trait Frontal EEG Asymmetry in Emotion p. 1998). Jones and colleagues used massage therapy to alter resting frontal EEG asymmetry (Jones. et al. An important next step would be to assess the infants of depressed versus non- depressed adoptive mothers. 1999). Debener. Recently. found. Jones and Field (1999) found in depressed adolescents that change in resting frontal EEG asymmetry could be accomplished in the course of a music or massage therapy session. (2000) examined 15 medicated depressed patients on two occasions separated by 2 weeks. they were able to reduce frontal EEG lateralization favoring the right with massage. demonstrating changes from the pre-test to the mid-treatment measure. Field & Davalos. 17 1999). In applying their efforts toward infants. Field & Davalos. No systematic change in asymmetry across sessions was . In their sample of 25 one-month old infants. Debener. To date. et al. 1998). and found adequate test-retest stability of EEG asymmetry only in control but not depressed subjects. Two studies have specifically examined the stability of asymmetry across time in individuals undergoing treatment for depression. then one would expect that there would be relatively little change in asymmetry as episodes of depression or other psychopathology wax and wane.. as expected. and perhaps to genetic risk. the magnitude of this asymmetry was attenuated during and after the session relative to a pre-session baseline (Jones & Field. While the asymmetries in their participants continued (at the group level) to demonstrate relative right activation. relatively greater left frontal activation in control than depressed subjects. If frontal EEG asymmetry is a trait related to risk. the data are somewhat mixed. as well as from mid-treatment to the post-test (Jones. for example. The anxious apprehension aspect of the model has . Some. study). have found that anxious individuals show relatively greater left frontal activation (Heller.63. Nitschke. the median intraclass correlations of stability was . Schnyer.. et al. 1998) have proposed a revised valence model. Heller and Nitschke (1997. State and Trait Frontal EEG Asymmetry in Emotion p. Also similar between the two studies was that the instability in the depressed subjects in Urry et al. 2000) with relatively greater right frontal activation. a symptom that cuts across both the anxiety and depressive disorder spectra. These studies have produced a pattern of results that the approach/withdrawal model cannot fully accommodate. Thus the majority of findings with depressed patients suggest some underlying stability across time (with the exception of the Debener et al.’s study. and asymmetry was not related to measures of daily mood. Tomarken and Henriques. Although the vast majority of clinically-relevant frontal EEG studies concern depression. 18 observed in the depressed patients however. By contrast. anxiety disorders have also been examined. & Hitt. with variations across occasions of assessment that have yet to be explained fully. et al. Others have associated panic disorder (Wiedemann. which is very similar to the test-retest values observed for control subjects in Debener et al. and across five assessments in five months for 12 of the subjects. the asymmetry was simply variable across sessions in these patients. Across three assessments in three months for all 23 subjects. (1999) found evidence of better stability in EEG asymmetry in a sample of women receiving a nonpharmacological intervention (Allen. 1999) and social phobia (Davidson. suggesting that anxious apprehension. 1997). may account for cases where anxiety or depression are not associated with the typical frontal asymmetry pattern. (1999) was not related to clinical status or mood state. Marshall. 1998). Urry. Etienne & Miller. " Some affective styles. State and Trait Frontal EEG Asymmetry in Emotion p. frontal EEG activation indexes what Davidson has called "affective style. In this way. put people at risk for depression and anxiety as part of a diathesis-stress process. Trait Frontal Asymmetry as a Predictor of State-dependent Changes in Emotion Whereas the previous section reviewed research suggesting that frontal EEG asymmetry may tap a diathesis to develop emotion-related psychopathology. Davidson (1998a) has proposed that trait EEG asymmetries index propensities for reacting in predictable ways to evocative stimuli. 402). but not those high in their measure of anxious apprehension. The following section reviews a handful of reports detailing ways in which people possessing different trait-like patterns of frontal EEG asymmetry respond to evocative stimuli. 19 intuitive appeal. and may reflect the relatively small sample size in each subgroup. ------------------------------------------------------------------- Insert table 3 about here ------------------------------------------------------------------- . 1998. Other findings in that study were not consistent with their model however. as it is reasonable to suppose that subvocal apprehensive ruminations may activate left anterior systems (Reid et al. analogous research has found that trait frontal EEG asymmetry predicts state-dependent emotional responses in the nonclinical range. Some support for the model comes from Nitschke et al. p.. or may suggest a need for further theoretical revisions of both the approach/withdrawal and the revised valence model of Heller and Nitschke (1997. he argues. (1999). 1998). who found that the expected pattern of relatively greater right frontal activation was present for subjects high in anxious arousal. State and Trait Frontal EEG Asymmetry in Emotion p. Together. but also that individuals with greater left frontal activation responded with more intense positive affect to positively valenced films.... Fox et al. In the adult literature. Wheeler. Davidson and Fox (1989) found that infants who cried in response to maternal separation had greater right frontal activation at rest than those who did not. but with a sample that had consistent asymmetries across multiple resting assessment occasions. With approximately the same design. considered jointly with those reviewed previously . and results indicated that individuals with greater right frontal activation at rest responded with more intense levels of negative affect to negatively-valenced film clips.g. Wheeler et al.. 20 Some of the earliest work of this sort investigated individual differences in state reactions in infants. et al. 1993). These specific affects were grouped into global ratings of positive and negative.g. Bell and Jones (1992). 1990). et al. these studies suggest that there exist individual differences in the propensity to respond emotionally given emotionally- evocative situations. (1992) added a longitudinal component to their investigation and determined that this effect was modestly stable over 5 months. Wheeler et al. Participants reported the intensity of their specific affects (e. fear. Tomarken. et al. (1990) asked participants to report affective responses to emotional film clips. (1993) found not only that individuals with greater right frontal activation responded with more intense negative affect in response to negatively valenced films. after taking EEG recordings at rest. particularly those involving fear (Tomarken. These studies. frontal EEG asymmetries have typically been related to global positive and negative affect in response to emotionally evocative films or slides (e. sadness) in reaction to the films. (1993) replicated and extended this work. a result subsequently replicated by Fox. suggest a process by which an individual's affective style might put them at risk for certain affective disorders such as depression and anxiety.e. 1998). Naumann. et al. Maier & Bartussek. For example. it was related to relatively greater left hemisphere activation at rest. it was in the direction opposite the prediction of the approach/withdrawal model. Becker. et al. (1993). they were inconsistent with the approach/withdrawal model posited by Davidson (1998b). 21 showing trait asymmetry may serve as a diathesis for emotion-related psychopathology. Davidson (1998b) points out that in Wheeler. It is important to note that at least one attempt to replicate these findings has not been entirely successful (Hagemann. For example. when Hagemann et al. (1998) opted to use normed emotion eliciting slides to evoke emotional reactions instead of using evocative films. that is. resting frontal EEG was recorded prior to emotion-evoking stimuli and the former was used to predict responses to the latter (Hagemann. et al.. et al. and eight minutes of eyes-opened and eye- closed resting EEG data. 1998a). For example. Hagemann. i. State and Trait Frontal EEG Asymmetry in Emotion p. However. using the Cz reference montage.'s (1998) results were due to methodological inconsistencies with earlier studies. et al.. or valence specific. . Davidson (1998b) has argued that Hagemann. (1998) did indeed find that individuals with greater left frontal activation at rest responded with more positive affect in response to positively valenced films.'s (1993) study. (1998) discovered a relationship between anterior temporal EEG asymmetry and negative affect. Their results were inconsistent. this effect did not generalize to frontal EEG recorded using a linked mastoids reference montage. To the extent that other significant results emerged. et al. 1998). Like Wheeler. biased reactivity (Davidson. Hagemann. certain affective styles may predispose people to emotion specific. 22 relationships were based on study participants with a demonstrated consistency in their frontal EEG pattern across three weeks. Davidson and Fox (1982)3 showed films of an actress performing happy and sad faces to infants who were 10 to 12 months old while recording EEG in the frontal and parietal regions. 1982). Further research is clearly required to resolve these inconsistencies. et al. Davidson. they argued. Davidson & Fox. States. Here. there is evidence to support this prediction (e. They found that these infants showed evidence of increased . in press..g. the literature highlighting fluctuations in frontal EEG asymmetry that are condition specific is reviewed. In early work. 1961). Ekman. 1990. but also proposes to accommodate state changes as well. are patterns of responses that are specific to certain environmental conditions (Cattell & Scheier. on the other hand. & Friesen. ------------------------------------------------------------------- Insert table 4 about here ------------------------------------------------------------------- The approach/withdrawal model of frontal EEG asymmetry is thought to pertain not only to individual differences in trait levels. Frontal EEG Activation Asymmetry as a State Measure Cattell and Scheier (1961) distinguished states from traits in the following way: traits.. environmental stimuli that encourage approach responses should result in relatively greater left frontal activation while environmental stimuli that encourage withdrawal responses should result in relatively greater right frontal activation. Indeed. That is. Coan. are predispositions to respond in particular ways over a variety of environmental conditions. State and Trait Frontal EEG Asymmetry in Emotion p. Fox and Davidson (1986) showed that infants as young as 2 to 3 days exhibited an increase in left frontal activation in response to a desirable flavor (sucrose). though no effect of the sad films was detected. Senulis and Friesen (1990) used emotional films to investigate the relationship between emotional experience and frontal EEG asymmetry in adults. they found that babies who cried in response to maternal separation showed an increase in right frontal activation (Fox and Davidson. 23 left frontal activation while viewing the happy films. State and Trait Frontal EEG Asymmetry in Emotion p. 1988) uncovered similar effects with both positive and negative affects. Interestingly. Ekman. while exhibiting more right frontal activation during the neutral flavor (water). in which case. unless the baby was crying concomitantly. sadness in the absence of crying was associated with relative left frontal activation in these infants. Fox and Davidson (1988) later found that both anger and sadness in response to maternal separation resulted in relatively greater left frontal activation. and in a way that would hold implications for emotion theory more generally. these researchers discovered that frontal EEG recordings averaged across the entire period of . 1988). 1987. Later Fox and Davidson (1987) showed that 10-month-old infants who reached for their mothers during a mother approach task showed more concomitant left frontal activation than infants who did not. Further. Fox and Davidson (1986. Using differently flavored drops. In a study that generally supported the approach/withdrawal over the valence model. 1987). Davidson. In subsequent years. Although in most studies of EEG asymmetry sadness is associated with relative right frontal activation. Saron. and in this case may reflect the infants’ attempt to regain the caregiver’s presence. anger and sadness appeared to result in relatively greater right frontal activation (Fox and Davidson. The authors reasoned that approach motivation may be involved in some sad states. This criticism is a legitimate concern in research of this type.. et al. 1990) have argued that the seeming dependence of state EEG asymmetry effects on moments during which participants are expressing emotions on their faces reflects the fact that emotional facial expressions are strongly tied to veridical emotional experiences. finding that Duchenne smiles resulted in more left anterior temporal activation than unfelt smiles. it was only during moments where participants made emotional facial expressions that effects emerged. Davidson and colleagues (Ekman. Ekman. Rather. et al.. a possible criticism is that the hemispheric differences identified in their work do not actually reflect differences in cortical activation. 1993) also revealed that Duchenne smiles resulted in greater left activation in frontal and anterior temporal regions than did unfelt smiles. 1990). their effects were mainly in the anterior temporal rather than the frontal region. although some have estimated that the effects of facial muscle alpha artifact are. with disgust films eliciting more right anterior temporal activation and happy films eliciting more left anterior temporal activation (Davidson. small . While this has theoretical appeal. Following up with the same data set.. A subsequent test of the effects of voluntarily performed Duchenne versus unfelt smiles (Ekman & Davidson. et al. et al. a finding that replicated what had been found in infants several years before (Fox & Davidson. 24 viewing the emotional films did not show evidence of differences in hemispheric activation (Davidson. 1990. Ekman. (1990) investigated the difference between Duchenne smiles (those involving activation of the obicularis pars lateralis muscle) and “unfelt” smiles. Davidson et al. 1988). but rather muscle artifact in the alpha frequency band (8 . 1990).. if significant.13 Hz) resulting from asymmetrical facial expressions. State and Trait Frontal EEG Asymmetry in Emotion p. Even then. 1993). fear. 1991). This and other work (e.. Harmon-Jones & Sigelman. Gotlib and Ranganath (1996) has shown that EEG asymmetry can covary with clinical state in the context of biofeedback training. Jones & Fox. joy and sadness. This is because disgust. 2000. withdrawal-related emotions resulted in a dramatic decrease in left frontal activation compared to both approach and control conditions. Baehr. State and Trait Frontal EEG Asymmetry in Emotion p. Though not designed to address the causal role of frontal EEG asymmetry. while anger and joy can be thought of as approach emotions (Coan. 25 (Friedman & Thayer. Ekman. and others have argued that facial muscle movement cannot alone account for cortical asymmetries. It is this more general model that was tested by Coan. et al. (in press) with voluntary facial expressions of these same five basic emotions. For example. even when facial movement is pronounced (Coan.. Baehr. et al. fear and sadness. work by Rosenfeld. Coan et al. in press).. 1993. et al. grouped and analyzed according the approach/withdrawal motivational model. can be thought of as withdrawal emotions. The steadily accumulating work on emotion and lateralized frontal brain activation might lead one to predict that disgust. 1994) of anger. (in press) discovered that when EEG data resulting from voluntary facial expressions of these emotions were grouped according to the approach/withdrawal model. fear and sadness would result in relatively greater right frontal activation while anger and joy might result in relatively greater left frontal activation. though most often thought of as negatively valenced.g.g. further . 1992) suggests that lateralized frontal brain activity is an important element in the collection of properties that comprise what appear to be distinct emotions or emotional families (see Ekman. consider five of the commonly hypothesized basic or modal emotions (e. Scherer. in press).. disgust. the increase in left frontal activation following an insult predicted self-reports of anger. Also. Harmon-Jones and Cavender (2000) used biofeedback training and found that the direction of EEG change systematically biased affective reports. Moreover. one in Harmon-Jones.. In a study designed to test specifically whether manipulating frontal EEG asymmetry would alter emotional responding. 2000). the increase in left frontal activation predicted the extent of aggressive retaliatory behavior. (2000) provided college students with a bogus radio broadcast indicating that an impending tuition increase that was either certain. Collectively these studies support the motivational approach/withdrawal . & Bohlig. in one experiment. as well as affective EMG responses. Harmon-Jones et al. State and Trait Frontal EEG Asymmetry in Emotion p. the degree of state-related change in left-frontal activation predicted coping actions (signing and taking petitions). Highlighting the state. The ability of state changes to predict subsequent emotion and behavior is further highlighted by a series of studies by Harmon-Jones and colleagues. Harmon-Jones. Sigelman. Subjects who heard that the tuition increase was under consideration showed greater increases in left frontal activation than those who thought it was certain. 26 suggesting that EEG asymmetry is linked to emotional states. in a manner consistent with the approach/withdrawal model (Allen. Allen. 2000. et al.and situation -specific nature of the relationship between state changes in EEG asymmetry and subsequent behavior. In two separate anger-induction experiments (one reported in Harmon-Jones & Sigelman. 2000). or merely under consideration. Sigelman and Bohlig (2000) found that only when coping responses were possible did left frontal activation occur in response to an anger-producing manipulation. among those who thought that the increase was merely under consideration. that these affective states include a motivational dimension (e. perhaps. highlighting not only that state-related changes in asymmetrical frontal activation occur in response to anger provoking situations. indicating. State and Trait Frontal EEG Asymmetry in Emotion p. Trait frontal asymmetry that is consistent across multiple sessions of measurement. but that such activation is seen when motivated behavior is likely to produce some resolution. We have also seen that frontal EEG asymmetries vary with certain affective states. whereas state-specific changes are thought to . State-specific changes in frontal asymmetry that characterize the difference between two conditions or between baseline resting levels and some condition. derived from resting EEG assessments 2.g. When conceptualizing the relationship between trait and state frontal EEG asymmetry. The primary differences between source #2 and source #3 are that: occasion-specific fluctuations are assumed to be characteristic of the individual4. independent of the intended experimental manipulations. 27 model of frontal EEG asymmetry. Occasion-specific but reliable variations in frontal asymmetry that characterize the variation in resting EEG assessments across multiple sessions of measurement 3. there are in fact three systematic sources of variation to consider: 1. The Relationship Between Trait and State Frontal EEG Asymmetry We have seen that resting measures of frontal EEG asymmetry appear to tap trait approach versus withdrawal orientations that predict the intensity of certain affective responses and that may place individuals at risk for certain affective disorders.. fear has behavioral withdrawal properties while anger has behavioral approach properties). Further. then a single assessment of trait levels would prove sufficient. 28 reflect changes in response to specific experimental manipulations. however. in fact. Recent evidence (Hagemann. This may not be the case. 32% of the sample) who were classified as possessing stable asymmetry. there may exist individual differences in the magnitude of occasion-specific fluctuations. If occasion-specific fluctuations were not sizable. meaning that 68% of the sample was classified as having unstable asymmetry. In the remainder of this discussion. Most studies of trait frontal asymmetry are not designed to allow for the separation of source #1 and source #2. . Wheeler et al. Both sources of variation. For example. are related to individual differences assessed with resting EEG. accounts for approximately 60%. with both being subsumed under the rubric of trait levels. presumably reflecting a stable trait. the distinction between trait levels and occasion-specific fluctuations will be collapsed. while the consistency across multiple sessions. (1993) selected a subset of 26 from among 81 women (i. 2000) suggests that reliable occasion-specific fluctuations account for approximately 40% of overall explained variance in resting frontal asymmetry. State and Trait Frontal EEG Asymmetry in Emotion p. Occasion-specific fluctuations are assumed to characterize the individual throughout the evaluation session. and can be considered jointly as trait variance in raising the question of how trait and state asymmetry may interact. whereas state-specific changes will by definition change with state manipulations. the limited data bearing on this distinction suggest it is relevant and will account for a sizable proportion of variance. as most studies entail solely a single occasion of measurement of resting frontal asymmetry.e. This is not because this distinction is unimportant. but also might include the possibility that there are certain ranges of asymmetry in which change may be more or less likely. In the correlated model. 29 Because trait resting frontal EEG asymmetries predict affective responses. This artifact model would also subsume the possibility that there exist artifactual constraints on the degree of change possible imposed by a curvilinear relationship between trait and state levels and the difference representing the change between them (c. there are no published studies that examine this relationship. and because affective responses are associated with certain state-dependent changes in frontal EEG asymmetry. there are at least four conceptual models that may prove useful in guiding and interpreting investigations: 1) the artifact model. in which simple linear correlations can express the degree of relationship. Conceptual Models for Understanding Trait-State Asymmetry Relationships When considering the nature of the relationship between trait levels of frontal asymmetry and state-related changes in frontal asymmetry. trait and states are clearly related. State and Trait Frontal EEG Asymmetry in Emotion p. and. it is reasonable to hypothesize that resting frontal asymmetry will predict the magnitude of state-dependent change in frontal asymmetry associated with certain affective states. 1988)5. 2000b. Hagemann. This could take the form of a simple a floor or ceiling effect. The second model for conceptualizing the relationship between trait levels and state changes in frontal asymmetry is the correlated model. . but the correlated model remains agnostic about how or why. although several works in progress in various labs suggest there may be such a relationship (Coan & Allen.f. Chapman & Chapman. 2000). To date. 2) the correlated model. The artifact model proposes that the level of the trait variable places artifactual constraints on the degree of state-related change possible. 3) the interactive model. 4) the orthogonal model. This is of course a null hypothesis. although the ultimate determinant of such responses will be an amalgam of trait potentials and contextual constraints. which asserts that state changes are simply unrelated to trait levels. The same brain circuitry might be evoked to produce trait and state effects. and would be deemed likely only if many adequately powered tests failed to find a relationship between state change and trait levels. simple linear correlations would be insufficient to account for the relationship because different trait levels interact with situations to produce nonlinear effects in state changes. For example. These limits are constrained by an individual's genotypes. 30 The third model for conceptualizing the trait-state relationship is the interactive model. Such a finding would not necessarily mean that the state and trait mechanisms are unrelated. An analogue to this idea is the concept of reaction range in the field of behavioral genetics.. A reaction range refers to the upper and lower limits for the phenotypic expression a given genotype. one might speculate that subjects with consistent extreme asymmetry across sessions (e. different levels of trait frontal EEG asymmetry may determine the "reaction ranges" of individuals’ state asymmetry responses. 1993) might be thought to have less potential for state-related change than subjects who are inconsistently trait lateralized or who have approximately symmetrical activity. with certain genotypes showing much more or much less change as a function of environmental variations. Wheeler et al.g. In this model. State and Trait Frontal EEG Asymmetry in Emotion p. . but the elicitors under state and trait situations could be orthogonal. Analogously. The final model for conceptualizing the trait-state relationship is the orthogonal model. State and Trait Frontal EEG Asymmetry in Emotion p. such that occasion variance can be accounted for and an optimally reliable trait-only factor can be extracted for subsequent analysis. while the trait specific factor accounted for approximately 60%. all RMSEA £ 0. 2000. All c2(df=33) £ 44. Thus. This trait-occasion model resulted in reasonably good fits to the covariance matrices derived from various cortical regions (fit statistics were collapsed across multiple cortical regions. see also Steyer. As mentioned above.85.08. 2000). ------------------------------------------------------------------- Insert Figure 1 about here ------------------------------------------------------------------- .71. Hagemann recommends constructing a model similar to his when conducting trait EEG asymmetry research. These results imply that trait cortical EEG asymmetries are highly sensitive to day-to-day subject variations or variations in how the subjects react to the experimental context. all CFI ≥ 0. concluding that occasion specific factors accounted for approximately 40% of overall explained variance. all p ≥ 0.084. all pRMSEA ≥ 0.215. 31 Data Bearing on the Trait-State Relationship There are few data available at present to test the viability of these models of the trait-state relationship. but data from two studies are germane. this model assumes that cortical asymmetries recorded on multiple occasions load first on occasion factors. Hagemann. see figure 1). Hagemann (2000) then computed coefficients of state and trait specificity. The first of these studies has been mentioned already: the state-trait structural model proposed by Hagemann (2000. 1992). These occasion factors then load on a single higher order trait factor (Hagemann. Ferring & Schmitt. 23. Coan and Allen (2000b) used resting frontal EEG (trait) to predict the change in frontal EEG asymmetries evoked with a Directed Facial Action (DFA) task where subjects were asked to perform voluntary emotional facial poses. a trait measure of frontal EEG asymmetry showed a predicted relationship to a trait variable: relatively greater left frontal EEG activation was associated with higher BAS scores (replicating earlier research by Sutton & Davidson. 1997).11. is how state-related changes would relate to either the trait or occasion factors.59. RMSEA £ . State and Trait Frontal EEG Asymmetry in Emotion p. CFI ≥ . With three different reference schemes. With both trait and state-dependent EEG asymmetry showing predicted relationships with trait and state manipulations respectively. Results using two of three reference schemes (average and Cz references) suggested that resting asymmetries were strongly related to the magnitude of change from resting baseline in approach state manipulations (model fit statistics for average and Cz reference schemes: c2 £ 10. however. The DFA manipulations resulted in state-dependent alterations in frontal EEG asymmetry. Path coefficients between latent trait frontal and state-change frontal asymmetry variables were uniformly .97. the association between frontal asymmetries at rest with state-dependent changes was assessed using confirmatory structural equation modeling (SEM). 1997. et al. p ≥ 0. Coan. In the same participants. 32 Missing from the Hagemann model. Coan and Allen (2000b) used trait measures of frontal EEG asymmetry to predict state change under experimentally manipulated conditions. the structural model did not fit data derived using the linked mastoids reference scheme). In a related analysis to specifically address this issue. Using a sample of data reported by Coan. and Harmon-Jones & Allen. (in press). et al. (in press) found that the withdrawal condition resulted in significantly lower left frontal activation relative to approach and control conditions. 05). path coefficients derived from this model mirror those of the other reference schemes exactly. RMSEA = 0.61. Path coefficients between latent trait frontal and state-change frontal asymmetry variables were again uniformly negative (- 0.00.46 for average and Cz reference schemes.. ------------------------------------------------------------------- Insert Figure 2 about here ------------------------------------------------------------------- The results of an identical structural model applied to changes during the withdrawal condition also suggested that resting asymmetries were strongly related to the magnitude of change from resting baseline in withdrawal state manipulations in two of three reference schemes (fit statistics for average and Cz reference schemes: c2 £ 7. Alternatively. respectively. suggesting that individuals who were more right frontally active at rest displayed a smaller difference in the right-activation direction during the withdrawal condition. p < 0. respectively. individuals who were more left frontally active at rest displayed a larger difference in the right-activation direction during the withdrawal condition. CFI = 1.61 and -0.70 and -0.47. the results suggest that individuals who are more left frontally active at rest display a smaller difference in the left-activation direction during the approach condition.05). p ≥ 0. the structural model again did not fit data derived using the linked mastoids reference scheme). p < 0. Alternatively. 33 negative (-0. . suggesting that individuals who were more right frontally active at rest display a larger difference in the left-activation direction during the approach condition (see figure 2). State and Trait Frontal EEG Asymmetry in Emotion p.65 for average and Cz reference schemes.00. While model fit was not achieved for the linked mastoid reference. Wheeler. Resting levels of frontal activation asymmetry have been shown to predict other trait-like measures such as shyness.. 1997.. Alternatively. et al.. Sutton & Davidson. 1999. et al. 1996. 1995. but anxiety. Schmidt... internalizing and externalizing problems as well (Dawson. et al. levels of behavioral activation. and even natural killer cell activity (Fox.. et al. State and Trait Frontal EEG Asymmetry in Emotion p. et al. an interpretation that is difficult to reconcile with any of the existing models of anterior asymmetry. 1990. but have the greatest room to move in the right- frontal direction. the attempt has been made to review most of the literature on frontal cortical EEG activation asymmetries. Finally. the correlated model would suggest an inverse relationship between trait levels and propensity for state-related change. 1993). Ekman. 1989. Gotlib. showing high internal consistency and acceptable test-retest reliability (Tomarken. sociability.. Davidson.. 1998. as reviewed above. et al.most notably depression. . Tomarken. Conclusion In this paper. et al. in press. it appears that frontal EEG asymmetry at rest predicts the magnitude of state-dependent affective responses (Davidson & Fox. which would suggest that individuals who are tonically most left-frontally activated are constrained from moving in the left frontal direction. Davidson. emphasizing the differences and similarities between its trait and state natures. 1990. is associated with psychopathology in children and adults . et al.. Resting levels of cortical activation asymmetries are fairly stable and trait-like. Henriques & Davidson. et al. 1991). State-related changes in frontal EEG asymmetry have also been shown to occur as a function of distinct affective states (Coan. 1999. 1997). 1999. trait anger. Resting frontal asymmetry. Wheeler & Kinney 1992). 34 These findings are perhaps most consistent with the artifact model. Harmon-Jones & Allen. Fox. approach oriented states and increases in relative right frontal activation being more associated with negatively valenced. Given recent . the interactive model and the orthogonal model. trait-like cortical activation asymmetries predict the magnitude of change in cortical asymmetries associated with specific affective states. An important question is whether. This model asserts that EEG asymmetries over the frontal cortex -- whether state-dependent or trait-like -. while relatively greater right frontal activation is related to a withdrawal orientation or action. results reported by both Hagemann (2000) and Coan and Allen (2000b) suggest that superimposed on trait asymmetries are reliable and sizable variations across occasions of measurement. the artifact model. Replication of the inverse trait-state relationship is obviously required before conclusive interpretations can be levied. 35 Davidson & Fox. Davidson. but in this instance negatively. with increases in relative left frontal activation being more associated with positively valenced. 1992. State and Trait Frontal EEG Asymmetry in Emotion p. related to state changes in response to experimental manipulations. but the limited findings to date suggest that trait levels can be sizeable predictors of state-related changes in frontal asymmetry. relatively greater left frontal activation is related to an approach orientation or action. According to the approach/withdrawal model. 1998a. This pattern of results has suggested a general framework for understanding frontal EEG asymmetries: the approach/withdrawal model (Davidson. This paper has proposed four models of trait/state associations. withdrawal oriented states. the correlated model. and that trait levels assessed at any given occasion are strongly. and to what extent. 1982).index approach versus withdrawal tendencies and actions. Though preliminary. 1998b). since it is the more general of the two. 36 findings cited here (Coan & Allen. An improvement in the fit statistics of such a model would lend credibility to the interactive model over and above evidence supportive of the artifact or correlated models. Neither Hagemann (2000) nor Coan and Allen (2000b) include multiplicative terms in their models. there remain inconsistencies that the model must explain or accommodate. A straightforward way of doing so initially would be to include multiplicative terms in a structural model. the intensity of emotional experience) would need to be included explicitly in related analyses. At present. To adequately test the interactive model. the interactive model is more satisfying than the correlated model as well. the orthogonal model is the only model at present that appears to be untenable. 2000). important questions about the nature of frontal EEG asymmetry remain. The limited data addressing these models to date is perhaps most strongly supportive of the artifact model. Thus although frontal EEG asymmetry appears to map well onto directional propensities to approach or withdraw .g. State and Trait Frontal EEG Asymmetry in Emotion p. Although the approach/withdrawal model appears to be the most parsimonious and best fitting account of the research to date. Hagemann. other relevant variables that might modulate the relationship between trait levels and state change (e. correlated or interactive models. Future Directions Apart from state/trait interactions. One can imagine a structural model based on Hagemann's data set wherein multiplicative terms representing the interaction of occasion and trait factors could be used to explain the observed variance in cortical asymmetries. the existing data can be interpreted in terms of either the artifact. Theoretically. 2000b. while not being so general as to ignore questions of how trait and state asymmetries may be related (as the correlated model does). numerous EEG epochs across 30 seconds or much longer are collapsed to produce a reliable estimate of spectral power. Frontal EEG asymmetry has inconsistently correlated with one measure of behavioral inhibition. the literature has just begun to address questions related to response thresholds and peak responses. rise time to peak.. As applied to frontal asymmetry. Other future directions have been proposed by Davidson (1998a). On the other hand. Further work. using multiple measures of behavioral inhibition. It includes measures of what he has called stimulus threshold. As of this writing. or whether it has no effect at all. no published reports chart response slopes or response recoveries with regard to fluctuations in frontal EEG asymmetry. the role of behavioral inhibition is at present unresolved. Affective chronometry refers to changes in affective states in magnitude over time. who suggested that individual differences in the time course as well as the magnitude of emotional responses are likely to be important for a deeper understanding of affective style. The lack of such reports is due in part to constraints imposed by the measure. EEG asymmetry is a dynamic process that may benefit from . will be necessary to clarify this relationship. It is also unknown whether behavioral inhibition attenuates or enhances changes in EEG asymmetry to approach and withdrawal related stimuli. Studies showing an increased likelihood to respond in certain affective directions given certain baseline asymmetry levels (e. right frontally activated babies being more likely to cry following maternal separation) provide compelling evidence of individual differences in stimulus thresholds. Davidson (1998a) has called for the measurement of what he calls affective chronometry. State and Trait Frontal EEG Asymmetry in Emotion p.g. 37 from environmental stimuli. and recovery time to baseline. peak response. 2000.. The attempt to understand the . frontal EEG asymmetry appears clearly to be related to affective processes -. An important direction for this program of research will be to better understand how. studies using behavioral genetics methods as well as studies specifically examining the effects of early environment will shed light on the genesis and malleability of trait levels of frontal EEG asymmetry. Research into state/trait frontal EEG asymmetry interactions will aid in these endeavors. and depressed subjects produce asymmetry scores indicative of relative left frontal activation on only 45% of epochs (Baehr et al. It is unknown whether similar variability will also be present in state-related epochs. Thus even though reliable group differences in trait levels may exist between clinical populations and control subjects. 1998).. Data that have examined the consistency of short (1 second) epochs of EEG asymmetry have found that nondepressed subjects produce asymmetry scores that reflect relative left activation on approximately 70% of epochs but relative right activation on the remainder (Allen et al. as well as the degree to which trait asymmetries can be systematically altered. State and Trait Frontal EEG Asymmetry in Emotion p. 38 examination using real time measures of asymmetry. state- fluctuations in frontal EEG asymmetries can be controlled. In sum. there is substantial variability within any individual over relatively short periods of time. advances in the cognitive neuroscience of emotion will likely shed light on the structural and functional underpinnings of cortical asymmetry. and the degree to which. or measures that are sensitive to short-lived perturbations from trait levels. 1998). Similarly..both stable and fleeting. While the underlying processes that drive frontal EEG asymmetry are not currently known. or whether state-related changes will minimize the ongoing variability seen in the trait recordings. Baehr et al. the alpha band (8-13 Hz) is lower or expanded downward. 3 In this and many infant studies. 2 Difference scores have been criticized for their greater unreliability than the constituent scores from which they are derived.. 1992) refer to alpha as being between 6 and 9 Hz in infants. Dawson. Davidson and Fox (1982) recorded from 1 to 12 Hz. but in most cases this criticism does not threaten the reliability of the results using an asymmetry difference score. et al. These latter effects could result from .. 4 Such fluctuations might reflect individual difference variables (e. Reid et al. 1992). Such effects would not be the result of the intended state-related experimental manipulations.g. Tomarken et al. Footnotes 1 Other issues related to this assumption are beyond the scope of the current chapter. State and Trait Frontal EEG Asymmetry in Emotion p. 39 relationship between frontal EEG asymmetry and various affective states and traits has resulted in a fruitful and multifaceted program of research. Other studies (e.g. mood on the day of assessment) or alternatively the interaction of the individual with the experimental milieu in a way that varies from session to session. Spydel & Sheer.f.. as alpha values at any given site tend to be highly reliable so that the difference score is also highly reliable (cf. but include the assumption that reduced alpha is an adequate measure of activation (c.. 1998. 1982) and the assumption that the alpha recorded at a given scalp site is indicative of electrical activity generated in the underlying cortical regions. The future of research in this area promises to be no less so. but rather an interaction of subject characteristics with general experimental milieu. the opposite artifactual relationship should obtain. 5 Chapman and Chapman (1988) present the case that mean difference scores will artifactually be largest when total accuracy (the sum of the constituent scores) is near 50%. state-related change) should be artifactually negatively related to the sum of state and trait scores. Such an artifact could augment or nullify any valid relationships that might exist between trait levels and state change. when trait levels have less variance than state levels.e. 2000). Extrapolating from the derivations of Chapman and Chapman (1988). 40 unintended variations across experimenters or an interaction of subject and experimenter characteristics (Kline. state-minus-trait asymmetry scores (i. . the factor that underlies the artifactual relationship. when trait levels have more variance than state levels. is relevant. State and Trait Frontal EEG Asymmetry in Emotion p. reliable variance. Although EEG asymmetry cannot be conceptualized in terms of accuracy. D.P. 33. Harmon-Jones..H. P. normal controls. Psychological Science.F. R. On predicting some of the people some of the time: The search for cross-situational consistencies in behavior. Obermeyer. C.M. (1966). & Arbisi.J. 89-92. 81. Rosenfeld..J. (1974). J. Benca... & Hitt. Personality and Individual Differences.B. 506- 520. E. S. 642-646. Larson. . Iacono.. Regional electroencephalographic asymmetries in bipolar seasonal affective disorder before and after exposure to bright light. Biological Psychiatry. 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Trait frontal EEG asymmetry and other trait-like measures Citation Sample Age info Sex Handed Reference Independent Variable Dependent Variable Results Summary n ness Scheme Davidson.7 F/M R Cz Positive affectivity (PA). low (LD) EEG @ F3/4. F/M R LM EEG @ F3/4. 29 22 . O1/2 sex. P3/4. Field. et al. and neuroticism (N). P3/4. _ SC Hagemann. et al. F R Cz. C3/4. Fox. Experimenter gender: same vs. LM Extreme LFA and RFA groups Natural killer (NK) cell.20 yrs. M R LM EEG @ F3/4. Understimulating (U) physio and beh. _ BAS. et al.. _ LFA _ defensiveness 25 men T3/4. in monkeys 14. 8. F7/8. R hemisphere preference EEG @ F3/4 & P3/4 _ LHP. F7/8 & T3/4 Natural killer (NK) cell activity _ RFA.. 36 Mean = 24.. P3/4 PANAS (PA & NA). _ BAS Allen. T3/4. scorers selected from among 271) . 1997 mothers. measures U babies. C3/4. F7/8. 56 Table 1. 12 W Mean = (Westerne 29.1 yrs. Malphurs (infants) (O) vs. P3/4 & O1/2 _ shyness. P3/4 _ NA. _ RFA et al. _ LFA Davalos. F7/8.. _ LFA _ defensiveness Kline. C3/4. (J vs W) . anger attitudes _ A. _ NK activity lymphocyte and T-cell activity Kalin. _ NA score 1996 _ LFA.. T5/6. 1998 60 women 17-33 years F/M R Linked Ears Defensive Coping (EPQ-L scale) EEG @ F3/4.21 yrs. _ RFA Harmon-Jones & 37 No info F R Cz EEG @ F3/4 & P3/4 BIS/BAS _ LFA. O1/2 For women. C3/4.. FP1/2. HD. et al.39 F/M R LM EEG @ F3/4. rs) Merckelbach. _ NK (rest) 1999 at rest. F No info A1 L vs. 40 18 . and _ RFA. 87 No info F/M No info Cz Baby groups: Overstimulating EEG @ F3/4 & P3/4. T5/6. _ NK (exam) following pos and neg film clips _ LFA. FP1/2. 1995 48 49 . State and Trait Frontal EEG Asymmetry in Emotion p. F3/4 & P3/4 Trait anger (A). T3/4.97 F R Cz Low shy vs High shy EEG @ F3/4. 2001 40 women 16 . BIS/BAS All subjects. _RFA (extreme yrs. _ BDI score Jones.53 yrs. et al. et al.. 24 17 ..6 yrs. For women.62 F/M No info Cz EEG @ F3/4. opposite.. _ NK (pos film clip) Fox. EEG @ F3/4.. in press 235 Mean = 20. (Mothers showed the same pattern as infants) Kang. A1/2 extroversion (E). 97 M = 19 yrs. P3/4 & O1/2 Social competence (SC) _ RFA.. 40 & 52 months Kline et al. _ LFA 40 men T3/4. O1/2 For men. BDI _ LFA. _ BASD. 2000 17 (rhesus Longitudinal F/M No info No info Extreme LFA and RFA groups Cerebrospinal fluid CRH _ RFA. _ LFA 2000a (AA) _ A*AA. T5/6. _ CRH monkeys) data @ 4. Harmon-Jones. LFA Moss. _ LATA 1999 negative affectivity (NA). Kline. before exam. F/M R Linked ears EEG @ F7/8. et al.38 yrs.4 F/M R No info High (HD) vs. 1985 12 J Mean = F R Cz Cultural group EEG @ T3/4 & P3/4 W = _ LPA (Japanese) 32. _ SC months _ LFA. et al. 1991 20 17 . _ LFA in presence of opposite defensiveness groups. _ LFA _ A. various O babies. _LFA 1996 (questionnaire) Schmidt. 1999 40 M = 20. FP1/2. RFA group. et al. C3/4 HD = _ LFA in F3/4 & F7/8 Davidson. (A) and T5/6. No effects in alpha band. F/M R LM EEG @ F3/4 7 & P3/4 BIS/BAS. T3/4. Low EEG @ F3/4. aggreeableness.. concientiousness (C). O1/2. _ RFA 1994 (extreme Low soc vs. low soc from among 271) Schmidt & Fox. EEG @ FP1/2. F/M No info No info Measures of openness (O).BIS diff score _ LFA. T3/4. 46 18 . Low soc vs. F7/8. State and Trait Frontal EEG Asymmetry in Emotion p. et al. 57 (extreme yrs. T3/4. LPA = Left parietal activation .. _ BAS 1997 _ RFA. P3/4. LFA = Left frontal activation RATA = Right anterior temporal activation. LM EEG @ F3/4. low soc = _ LPA selected from among 282) Stough. F7/8.22 yrs. _PA 1992a C3/4 affect (PA and NA) _ LFA. et al. F7/8. LATA = Left anterior temporal activation RPA = Right Parietal activation. high soc had _ LFA than selected high shy. High soc _ soc. A1/2 & _ soc. _ LFA scorers high shy. 40 No info F R Cz Low shy vs High shy EEG @ F3/4. BAS . F R Cz. _ BAS-BIS diff Tomarken & 90 No info F R Cz High Defensive (HD) vs. P3/4. _ NA RFA = Right frontal activation.30 yrs. 2001 16 20 . High soc O1/2 low shy. 90 17 . General positive and negative _ LFA. high soc = _ RPA scorers low shy. _ BIS _ LFA. 1994 Defensive (LD) & P3/4 Tomarken. C3/4.21 yrs. Sutton & Davidson. F3/4. and Fz in alpha 1 (8-10Hz). C3/4. F7/8. left visual field (LVF) appears to account for group differences vs right visual field (RVF) in self-report ratings of happiness in response to lateralized picture presentations Dawson. _ RFA F7/8.15 F/M No info LM Depressed (D) vs. insecure (IS) attachment Debener. depressed vs. _ LFA. Alpha 1: Phobics. Recovery vs. et 26 infants 11 . D. et al. LFA in F3/4 Bruder..23 F/M R Cz Happy. EEG @ AF1/2. Hessl (54 with months (ND) mothers affection behaviors (AB) (D & _AB).. State and Trait Frontal EEG Asymmetry in Emotion p. TP9/10. 1999 depressed mother vs. Major depression MD.. et al. P3/4. months stimuli. maternal separation (MS). non-depressed EEG @ Fp1/2.13 Hz) Davidson. 1998 24 (13 43 . Cz. P9/10. _ LFA (across other conditions) Panagiotides. 117 infants 13 . between RVF and LVF presentations depressed. non. P7/8. FT9/10. non-depressed Infant EEG @ F3/4 & P3/4.. 58 Table 2. F3/4. 1993 8 (4 with No info F R Cz SAD (S) vs control (C) groups. EEG @ F3/4. 20 (10 18 . depressed (D) vs non-depressed D. 99 infants 13 . Interaction with Yamada et al. _ LFA et al. _ AB Panagiotides. familiar adult mothers) Dawson. _ temporal stability in asymmetry Earnest. et al. et al. 1992 months w/mother (P).15 F/M No info LM Depressed (D) vs.17 F/M No info Cz Emotion conditions (play Infant EEG @ F3/4 & P3/4 S: If D. (59 with months (ND) mothers. SAD) Baehr. (54 with months (ND) mothers. 2000 37 (15 23 . _ LFA compared to SD 1997 depressed (MD) vs. non-depressed Infant EEG @ F3/4 & P3/4 D. C3/4. F7/8. and alpha 2 (10 . FP1/2. _ RFA (ND) mothers.64 F/M L/R (most Linked Depressed (D) vs.. 28 19 . D. controls . Frey. T7/8. F3/4. T3/4. Depressed (D) vs. 30 infants 11 . et al.57 F/M No info Cz Depressed (D) and non-depressed Percent time spent with RFA D. non-depressed Infant EEG @ F3/4 & P3/4 D. 2001 53 18 .. _ LFA Panagiotides et al. Klinger. P3/4.. 1999 depressed mothers) Dawson. Frey..15 F/M R/L LM Depressed (D) vs. O1/2 C. non-recovery In women: non-responders. but not stable over time depressed) yrs. Frey. negative faces in D group 1997 depressed (ND) mothers Dawson. P3/4 Group differences in frontal asymmetry 1985 depressed) yrs. _ pct time with RFA depressed) yrs. T5/6. secure (S) vs. sad & neutral face EEG @ F3/4. pictures. F No info Cz Pre and post biofeedback BDI score Lower BDI score post treatment study) treatment to _ LFA .. stranger approach during P (SA). (ND) groups (BDI median split) vs. FC5/6. Sub-depression (SD) mothers) Dawson. R) Earlobes (ND) groups C3/4. non.17 F/M No info Cz Emotional faces during emotional Infant EEG @ F3/4 & P3/4 Bilateral decrease in activation during Panagiotides et al. 1999 1 (case 14 yrs. et al. from depression following CP5/6.. anticipating public speech T3/4. P3/4 (alpha S _ LFA seasonal Pre-post bright light treatment power reviewed here) Unchanged by treatment affective disorder.68 F/M R LM Social phobics vs.. 117 infants 13 . _ RFA/RATA 2000 yrs.65 F/M No info Nose Resting EEG @ F3/4. _ LFA al. SSRI (Fluoxetine) treatment O1/2 Davidson. P3/4. Trait frontal EEG asymmetry and measures of psychopathology Citation Sample Age Sex Handed Reference Independent Variable Dependent Variable Results Summary n info ness Scheme Allen. . depressed (ND) groups (BDI). depressed P3/4 Aap no _ LFA (D). 1996 96 46 . 2 mean = Depressed (D) vs. PO1/2 _ left anterior temporal activation in Study 2: 27 27. 2000 160 Mean = F No info Cz Depressed (D) vs. info therapy.57 F/M R Cz. 50 No info F/M R Nose Resting EEG and electrodermal EEG @ FP1/2. T5/6. (13 trend in AR reference) depressed) . F3/4.8 No No info Cz Music (Mu) vs. A1/2. T3/4... anxious arousal (AAr). suggesting no cognitive (Nev) groups mediation Henriques & 14 (6 Dmean: F/M R Cz. mood/cognitive PD. state Anxiety decreased post exercise. EEG @ Fp1/2. _ Neg affect depressed (longitudi pattern stable mothers) nal) Nitschke. 1990 previoiusly 37. _ LFA yrs. LFA 1994 yrs. Henriques & 28 (15 31 . et al. panic (P) vs. F7/8. _ EDA (T1 and T2). et al. and yrs. massage (Ma) Depression measures & EEG LFA increased from pre to during. non-depressed A1/2. 2) T3/4. LM. O1/2. co-morbid (CM) & control groups (C) Papousek. _ LFA Study 2: 59 Depressed (D) & Never depressed measures No other effects. 1998 Study 1: 77 No info F R Cz Previously depressed (PD). Fox. et al. F3/4. 59 study) treatment to _ LFA Field. TCP1/2. AR 1) Depressed (D) vs. 1998 of during to post depressed mothers Jones. _ E months (E) and Internalizing (I) (_ S & _RFA). P3/4. 1998 (35 with (ND) mothers vagal tone D. 1991 depressed) yrs. FTC1/2. non-depressed Infant EEG @ F3/4 & P3/4 D. F7/8. 1999 67 17 . non-depressed EEG @ F3/4. 1998 Study1: 36 1 mean = F R Cz. during & post tests @ F3/4. D. Externalizing (_ S & _RFA). T3/4. _ RFA LM: no effects Heller. non-depressed Infant and mother EEG @ F3/4 D.4 yrs. Pre. T3/4.. non-depressed Infant and mother EEG @ F3/4 D. P3/4 from during to post in both Mu and Ma Jones. State and Trait Frontal EEG Asymmetry in Emotion p. F7/8..20 F/M R A1 Anxious apprehension (AAp).. F7/8... et 63 infants 1 week F/M No info Cz Depressed (D) vs. P3/4 A. Field & 25 infants 1 month F/M No info Cz Pre..54 yrs. et al. _ LFA al. Petruzzello. non. conditions measures of anxiety level increased post exercise. D. infants depressed Fox. D. C3/4 D. et al. AAr. depressed). LM Never depressed (Nev) & EEG @ F3/4. et al. worry (W) (A & P).7 M R LM Pre and Post rigorous exercise EEG @ F3/4. (ND) groups P3/4. T5/6. 19 M = 22. EEG @ F3/4. _ RFA (23 with months (ND) mothers _ RFA. C3/4 AR: D..8 (ND) mothers and their respective & P3/4 100 non. et al. non-depressed Infant EEG @ F3/4 & P3/4. Reid. P3/4 If _ RFA AND _ anxiety.7 yrs. during and post massage Infant EEG @ F3/4 & P3/4 _ RFA from pre to during and from Davalos. LM. D & ND not different (both studies) (17 18. Field. AR Depressed (D) vs. et al. 3 F/M No info Cz Depressed (D) vs. in LM reference. Depression (D) and Anxiety (A) measured. 1995 32 3-6 F/M R Cz Depressed (D) vs. 1997 44 infants 1 month. _ RFA (mothers and infants) months (mothers) (ND) mothers & P3/4 Field. _ I Gotlib.62 F/M No info Cz EEG @ F3/4. _ RFA tasks Jones & Field. _ RFA (mothers and infants) Depressed. _ Vagal tone depressed mothers) Jones.53 yrs. previously depressed (PD) groups P3/4. Cz: D. P3/4 & O1/2 Sociability (S). _ EDA 2001 activity (EDA) at two time points If _ LFA AND _ depression. T5/6. C3/4. _ RFA Davidson. 1999 30 M = 18. _ LFA anxious) groups.. et al. _ LFA Davidson. 17. T5/6. (ND) groups (SCID) depressed (Study 2. et al. 1997 40 (24 No info F/M R LM Anxious (A) & control (C) EEG @ F3/4. _ RPA depressed) Cmean: 34. T3/4. EEG @ F3/4. 5 No info F/M R Cz EEG @ F3/4 Pre and post therapy session Subjects with _ LFA at beginning of 1996 reports of affect. 60 Study 2: 27 27. State and Trait Frontal EEG Asymmetry in Emotion p. 1983 15 (6 No info F/M R Cz High vs low BDI scores EEG @ F3/4.. (ND) groups (SCID) depressed (Study 2. P3/4 _ BDI. motor task (M) RFA = Right frontal activation. median intraclass in depression correlation = . panic stim (Pn). neutral stim A: P. anxiety stim P. 1999 23 18-45 F R Cz. _ RFA disorder) (N). _ RFA 1999 panic yrs. emotional stim (E). _ LFA when shown erotic pictures (A). F7/8.63 Schaffer. affect change session show _ change from neg to pos (AC) score affect Urry et al.. et al. LM. 48 (23 with M = 36. Asymmetry stable across 3-5 monthly Depressed stability of asymmetry over time others not reported assessments.. et al. (13 trend in AR reference) depressed) Rosenfeld.54 yrs.55 F/M R Cz Panic (P) vs. T3/4. P3/4 Rest: P. Conditions: rest (R). LATA = Left anterior temporal activation RPA = Right Parietal activation. LFA = Left frontal activation RATA = Right anterior temporal activation. in LM reference. LPA = Left parietal activation . EEG @ F3/4. AR Time of Assessment – to examine EEG @ F3/4. et al. control groups (C). _ RFA depressed) Weidemann. . _ NA 1990 yrs. 2) 13 (cross. 2) 7 . crying) infants sectional).4. 1992 1) 33 1) 14 . P3/4 Infant response to maternal Criers.44 F/M R Cz. affective bias Cz. all in response LM reference: No effects to affective slides. LM EEG @ F3/4. C3. _ PA-NA following film clips difference _RFA. P3/4. not. 61 Table 3. C3/4 Reported positive affect (PA) _ LFA. _ R T3/4. State and Trait Frontal EEG Asymmetry in Emotion p. et al. Positive affect (PA).. _ LFA crying) Fox. T3/4. et al. negative Cz. et al. _ RFA infants months separation (crying vs. 90. _ PA 1998 yrs. _ NA analyses following film clips based on 26 with stable asymmetry across sessions RFA = Right frontal activation. and negative affect (NA) _ RFA. _ PA reactivity (GR). Trait frontal asymmetry as a predictor of state dependent changes Citation Sample Age Sex Handed Reference Independent Variable Dependent Variable Results Summary n info ness Scheme Davidson & Fox.. LPA = Left parietal activation . 13 infants 10 months F R (Parents) Cz EEG @ F3/4. 37 19 . 8 min resting: _ LFA. 4 min eyes clsd: (AB). and negative affect (NA) _ RFA. et al.12 months (longitudi nal) Hagemann. P3/4. not. _ PA 1993 most yrs. _ NA note: overall results equivocal with regard to A/W model Tomarken.and generalized _ LFA. _ RFA 1989 separation (crying vs. 32 17 . LATA = Left anterior temporal activation RPA = Right Parietal activation. P3/4 Infant response to maternal Criers. LFA = Left frontal activation RATA = Right anterior temporal activation.24 F/M R/L Cz EEG @ F3/4. Non-criers.41 F R Cz EEG @ F3/4.. T3/4. C3/4 Reported positive affect (PA) _ RFA. but 17 -21 F R Cz EEG @ F3/4. A1/2 affect (NA). T3/4. Effects consistent over time. _ Fear report Wheeler. P3/4. _ RATA Duchenne (D) vs unfelt (U) smiles Fox & Davidson. _ RFA (_ LFA if vocalizing) Fox & Davidson. _ LFA than U 1987 months mother approach (MA). during emotional film clips se. C3/4. sad C3/4. 41 16 – 39 F/M R LM Pre (PRE) and post (POST) EEG EEG @ F3/4. et al. T3/4. 1999 17 35 . maternal condition). et al. et al. P3/4 MA.. 24 18-45 yrs. Waking EEG correlated with sleep yrs.. no effect Davidson. _ RATA Joy (face). P3/4. Frontal EEG Activation Asymmetry as a State Measure Citation Sample Age Sex Handed Reference Independent Variable Dependent Variable Results Summary n info ness Scheme Allen. P3/4 O1/2 (S) and neutral (N) Davidson. 24 infants ~ 10 F No info Cz Films of an actress performing EEG @ F3/4. 62 Table 4. 2000 36 F/M R Cz. F7/8.41 F R Cz Emotional facial expressions EEG @ F3/4. F7/8. 1990 31 17 . _ RFA Coan. 1992 21 infants 21 months F/M No info Cz Baseline (B) vs. et al.41 F R Cz Emotional facial expressions EEG @ F3/4. _ LFA expressions grouped according to P3/4 A=C approach (A). P3/4. stages (REM. _ LATA Davidson & Fox. freezing Those with most _ LFA to 1993 monkeys months time in response to challenge Benzodiazepam showed longest duration freezing behavior Dawson. LM. during emotional film clips. FTC1/2. T5/6. O1/2 Men: _ POST mood. C3/4. P3/4 D. and _ corrugator activity Activation Benca. P3/4. FP1/2.. “mother out” EEG @ F3/4. 9 Rhesus ~ 12 F/M No info LM Benzodiazepam shot vs vehicle EEG @ F3/4.63 F/M R LM Wakefulness vs various sleep EEG @ F3/4. et al. T3/4. withdrawal (W) and control (C) conditions Collet & Duclaux. P3/4 Benzodiazepam. T3/4. et al. T1/2. C3/4. Disgust (face). _ LFA press women yrs. SWS) P3/4 O1/2 (notably REM) in frontal and temporal regions Blackhart. A & S (crying). hook-up mood ratings T3/4.. 11 17 . _ RFA sadness (S). F/M R AR Emotional expression during EEG @ F3/4. P3/4 _ overall frontal activation during MO (MO) conditions Ekman & Davidson. 9 Rhesus ~ 12 F/M No info LM Benzodiazepam shot vs vehicle EEG @ F3/4. AR Voluntary emotional facial EEG @ F3/4. _ LFA (mother reach sub- 1986 months approach (MA). T5/6. et al.. T3/4. anger (A). Women: _ POST mood. D _ LFA. mother EEG @ F3/4. StgII. T5/6. P3/4 Happy.. anger face (A) T5/6. LATA 1993 (U) vs. (_ LFA if vocalizing) separation (MS) condition MS + crying. U.. et al. _ asymmetry towards Left or Right EMG zygomatic. P3/4 No effect of films per 1990 yrs. _ LFA 1982 months happy vs sad faces Sad.. 35 infants ~ 10 F R (parents) Cz Stranger approach (SA). _ LATA yrs. F7/8. O1/2 D _ LFA than A Ekman. W. unfelt (U) smiles . Happy (H). _ LFA expressions of joy (J). EEG @ F3/4. Facial _ RFA caused _ positive affect. _ LFA 1992 monkeys months Davidson. P3/4 D. State and Trait Frontal EEG Asymmetry in Emotion p.. F7/8. No effects 1986 emotional films. T3/4. 14 No info F/M No info LM Duchenne (D) vs unfelt smiles EEG @ F3/4. 2000 18 18-38 F R Cz Biofeedback training to move Self Report Emotion. Facial A & S (no crying). in 36 men. et al. Duchenne (D) vs. C3/4. 35 infants ~ 10 F R (parents) Cz Stranger approach (SA) vs. T3/4. P3/4. T3/4.25 F/M R LM Reward (R) vs. EEG @ Fp1/2. Reeves.A _ LFA control (C) groups by 1 cigarette Smoking itself. O1/2. _ RFA sadness (S).22 F R Cz Emotional facial expressions EEG @ F3/4. et al.3 Hz band: 1988 during taste conditions (sucrose H20. 16 infants 2 . no occular EEG @ FP1/2. _ LFA during H negative (N) affectivity groups N. T3/4. _ LFA (LE). disgust (D). O1/2. no reward AF3/4 Men: HE. positive (P) vs P. P3/4. 2000 (NI) conditions. _ RFA (in normals) yrs.12 Hz band: H20. 2001 artifacts in EEG recordings.. P. EEG @ F3/4. _ LFA "anticipation" (A) and 2 cigarette "no wait" (N) groups (2 X 2 factorial) RFA = Right frontal activation. during videos of anger (A). et al. 1992 23 18 . LFA = Left frontal activation RATA = Right anterior temporal activation. _ RFA happiness (H). 1994 16 21 . No effects of occular artifact in the alpha Naumann. Harmon-Jones & 42 No info M R LM Baseline (B). 1989 16 20 . not NI F7/8. O1/2 range. O1/2 S _ RFA. P3/4. T3/4. 1999 72 M = 26. _ LFA yrs. (P) and negative (N) scenes N. EEG @ F3/4. _ R. 30 Mean = F/M R Cz Imagination and film conditions. State and Trait Frontal EEG Asymmetry in Emotion p. F7/8. conditions sadness (S) during conditions.35 F/M R No info Various self-report measures EEG @ F3/4. and D. Hand response levels: left (LT) and right (RT).36 F/M No info Cz Occular artifacts vs. _ LFA 64. T5/6. medium (ME) and low RT. LATA = Left anterior temporal activation . large punish Women: LE. Anger (A) Zinser. _ LFA 6 . F3/4. P3/4. _ LFA yrs. _ RFA (HE). FL) responses Tucker & Dawson. et al.. TP3/4. _ LFA 2001 19 (LR). valarian (VN). F7/8. _ AG. S. citric acid [CA]. aggression (AG). F7/8.50 F/M R LM TV segments depicting positive EEG @ F3/4. S. 14 method No info F/M R LM Imagination condition.3 days F/M R (parents) Cz Emotional facial expressions EEG @ F3/4. _ RFA S. _ A. 60 Mean = F/M L&R Cz Incentive levels: Large reward EEG @ F3/4. P3/4 1 . C3/4. P3/4 LFA correlated with Aggression in I. et al. _ LFA (NR). P3/4. O1/2 P. H20). _ LFA yrs. C3/4. _ LFA Gilbert. reward (R). depressed EEG @ F3/4. punishment (P) Ratings of happiness (H) vs R. _ RFA EEG @ F3/4... vanilla (V). _ RFA Sabotka. _ LFA (LP). _ RFA during H Kline. C3/4. P3/4 H.3 F/M R Cz Cigarette deprivation (D) and EEG @ F3/4 D. T5/6 Miller & Tomarken. V. neutral (N). no-insult Self-reported anger (A) and I produced. et al. LFA correlated with Anger in I.2 yrs. Approach (finger press. _ LFA Sigelman. FP) vs withdrawal (finger lift. Expectency levels: high LT. insult (I).. 1992 15 18 . not NI Jones & Fox. punish (P). 63 Fox & Davidson. C3/4. _ RFA [S]. Response levels: active (A) and passive (PS). (others) Hagemann & 31 19 . P3/4 _ BDI. 2000 49 Mean = F No info No info Odor conditions. C3/4. F3/4. et al. compared to D 1984 actors (D) vs sexually aroused (S) Waldstein. O1/2 H _ LFA compared to A 2000 24 years Happiness (H) vs. LPA = Left parietal activation . 64 RPA = Right Parietal activation. State and Trait Frontal EEG Asymmetry in Emotion p. F7/8. P3/4.94.11) but not the linked mastoid scheme (c2 £ 45.00.59. T3/4. RMSEA £ 0. 65 Figure captions Figure 1. RMSEA = 0.23. 2000.42).73. all RMSEA£.) Figure 2.215.61. C3/4.71.08.85.52. all p≥. CFI ≥ 0.40). F3/4. Findings here were summarized across eight scalp regions (Fp1/2.00. State and Trait Frontal EEG Asymmetry in Emotion p.084. p = 0. all pRMSEA≥. RMSEA £ 0. CFI ≥ 0. p ≥ 0.00.71. 2000b) .00) but not the linked mastoid scheme (c2 = 48.97. Trait-state interaction model. All c2(df=33)£44. O1/2). all CFI≥. Fit statistics for models relating latent trait and approach state-change frontal asymmetry variables reveal good fits to data derived using the average and Cz reference schemes (c2 £ 10. T5/6. from Hagemann. p ≥ 0. RMSEA = 0. Path coefficients for each reference scheme are listed in the diagram (from Coan & Allen. Fit statistics for models relating latent trait and withdrawal state-change frontal asymmetry variables reveal good fits to data derived using the average and Cz reference schemes (c2 £ 7. CFI = 0. Trait/state-change confirmatory structural equation models.47. p ≥ 0. CFI = 1. Figure 1. . 05 level.69* LM Trait With Change During Withdrawal State TRAIT F78 CHANGE F78 -0.71* AR 0. Trait With Change During Approach State TRAIT F78 CHANGE F78 -0.92*LM 0.76* LM TRAIT FTC12 CHANGE FTC12 1.65* CZ 0.77* LM TRAIT FTC12 CHANGE FTC12 1.91* CZ 0.71* AR 0.90* CZ -0.61* AR 0.00* AR 0.70* AR 0.Figure 2.75* LM 0.93* CZ 0.73* AR 0.77* CZ 0.00* AR 0.74* AR -0.91* LM 0.98* CZ 0.94* CZ 1.94* LM 0.37* CZ 0.46* CZ 0.79* CZ 0.77* CZ 0.76* LM 0. .00* CZ 0.77* LM 0.93* LM 0.74* AR -0.94* CZ -0.77* CZ 0.95* AR 0.85* LM 0.71* AR 0.82* AR 0.87* LM TRAIT F34 TRAIT STATE CHANGE F34 0.71* LM * = Path coefficient is statistically significant at the p < 0.67* AR 0.80* LM TRAIT F34 TRAIT STATE CHANGE F34 0.63* AR 0.