BRAIN

March 25, 2018 | Author: asim801 | Category: Cerebrum, Brain, Anatomy, Zoology, Neurology


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THE EARLIER STUDIES ON THE LOCALIZATION OF THE BRAIN FUNCTIONINGSubmitted To: Miss Sumaya Submitted By: 3rd Group Sehrish Mamoor Sarah Anila PSYCHOLOGY DEPARTMENT UNIVERSITY OF PESHAWAR 2 BRAIN The brain is the portion of the central nervous system in vertebrates (animals with bones) that lies within the skull. In humans, the brain weighs about 3 pounds. Differences in weight and size do not correlate with differences in mental ability. The brain is the control center for movement, sleep, hunger, thirst, and virtually every other vital activity necessary to survive. The brain is a pinkishgray mass that is composed of about 10 billion nerve cells. The nerve cells are linked to each other and together are responsible for the control of all mental functions. The brain is divided into three major parts, the hindbrain (including the cerebellum and the brain stem), the midbrain, and the forebrain (including the diencephalons and the cerebrum). WHAT IS MEANT BY BRAIN LOCALIZATION? BRAIN LOCALIZATION: The brain exhibits "localization of function." This means that different parts of the brain carry out different functions (e.g., vision, control of voluntary movement, understanding speech, etc.) And, conversely, that not all parts of the brain do the same thing. BRIEF INTRODUCTION OF LOCALIZATION (BRAIN FUNCTION): It refers to the concept that different areas of the brain control different aspects of behavior. Theories of localization first gained scientific credence in the 1860s with Paul Broca's discovery that damage to a specific part of the brain—the left frontal lobe—was associated with speech impairment. Other discoveries followed: in 1874, Carl Wernicke identified the part of the brain responsible for receptive speech (the upper rear part of the left temporal lobe, known as Wernicke's area), and in 1870 Gustav Fritsch and J. L. Hitzig found that stimulating different parts of the cerebral cortex produced movement in different areas of the body. By the beginning of the twentieth century, detailed maps were available showing the functions of the different areas of the brain. 3 BRIEF HISTORY OF IDEAS ABOUT LOCALIZATION OF THE BRAIN FUNCTION: The 1st era, antiquity to the 2nd century AD. The history of the localization of the brain function can be divided into roughly 3 eras. During the 1st era which spans from antiquity to about the 2nd century AD, debate focused on the location of the soul i.e. what part of the body housed the essence of being and the source of all mental life, in an early and particularly prophetic Greek version of localization of function. Soul was thought to be housed in the several body parts including head heart and liver but the portion of the soul associated with intellect was located in the head. the individual who has been viewed by many historians as having the greatest influence during this era was Galen (130-200AD), an anatomist of Greek origin. Using animals he performed experiments that provided evidence that the brain was the center of the nervous system and responsible for sensation, emotions and thinking. ARISTOTLE: In the fourth century B. C., Aristotle considered the brain to be a secondary organ that served as a cooling agent for the heart and a place in which spirit circulated freely. He designated the space in which all the spirits came together as the sensus communis -- the origins of our much more metaphorical term, "common sense." Aristotle had famously written, "There is nothing in the intellect that is not in the senses." As we can see, he meant this quite literally. ALEXANDRIAN: By the first century A. D., Alexandrian anatomists had provided a general physical description of the brain. Basic structures such as the pia mater and dura mater (the soft and hard layers encasing the brain) were identified in addition to the basic divisions of the brain itself. Building upon this research in the next century, the Roman physician Galen concluded that mental actively occurred in the brain rather than the heart,Galen concluded that the brain was the seat of the animal soul -- one of three "souls" found in the body, each associated with a principal organ. The brain was a cold, moist organ formed of sperm. 4 THE MIDDLE AGE; In the middle Ages, the anatomy of the brain had consolidated around three principle divisions, or "cells," which were eventually called ventricles. Each cell localized the site of different mental activity. Traditionally imagination was located in the anterior ventricle, memory in the posterior ventricle, and reason located in between. AVICENNA: The Islamic medical philosopher Avicenna wrote in the early eleventh century that common sense was housed in the "faculty of fantasy," receiving "all the forms which are imprinted on the five senses." Memory preserved what common sense received. By contrast, the great anatomist Mondino de' Liuzzi wrote in his Anatomy (1316) that common sense lay in the middle of the brain. 16TH AND 17TH CENTURY: Sixteenth and early seventeenth-century anatomists contributed a great deal to the physical description of the brain--terms such as cerebrum, cerebellum and medulla. EARLY VIEWS: During the second half of the first millennium BC, the Ancient Greeks developed differing views on the function of the brain. It is said that it was the Pythagorean Alcmaeon of Croton (6th and 5th centuries BC) who first considered the brain to be the place where the mind was located. HIPPOCRATES: In the 4th century BC Hippocrates, he believed the brain to be the seat of intelligence, and the controller of the senses, emotions, and movement, and was the first to recognize that paralysis occurred on the side of the body opposite the side of a head injury. 5 ARISTOTLE: During the 4th century BC Aristotle thought that, while the heart was the seat of intelligence, the brain was a cooling mechanism for the blood. GALEN: He concluded that, as the cerebellum was denser than the brain, it must control the muscles, while as the cerebrum was soft, it must be where the senses were processed. Galen further theorized that the brain functioned by movement of animal spirits through the ventricle.... DESCARTES: Descartes (1596-1650) introduced the concept of a separate mind and body. He believed that all mental functions were located in the pineal gland, a small centrally-located brain structure which is now believed to play a role in sleep/wake and dark/light cycles. PAUL BROCA: The clinical approach was pioneered by the French physician Pierre Paul Broca. In a classical work, carried out around 1860, he studied the brain of several aphasic patients (that is, they could not talk).After his death, Broca discovered that Tan's brain had a relatively small zone destroyed by neurosyphillis, which was delimited to one side of the anterior brain hemispheres (cortex). This part of the brain later became known as Broca's area, and it is responsible for the control of speech (motor expression of the language). His studies were confirmed by several neurologists, including John Hughlings Jackson, the doyen of British neurologists, who was able to confirm the laterality of function in aphasic patients, and to provide a major conceptual integration of functional localization in the brain, by means of his "hierarchical" theory. 6 CARL WERNICKE: A German neurologist, Carl Wernicke, discovered a similar area in the temporal lobe, which, when lesioned, led to sensory deficit in language, i.e., the patient was unable to recognize words, although he or she could hear sounds quite well. Wernicke thought that his area (which was named after him) was connected by fiber systems to Broca's area, thus forming a complex system responsible for understanding and talking. GUSTAV FRITSCH AND EDUARD HITZIG: They discovered that the stimulation of some areas caused muscle contractions in the head and neck, while the stimulation of distinct brain areas caused contractions of the forelegs or hindlegs, thus providing the first evidence for a finer localization of function in the cortex, and starting a whole new paradigm for mapping the brain. By the end of the nineteenth century, the concept of brain localization was firmly established in the neurosciences. The next century would witness the use of increasingly sophisticated techniques in animals and humans, which were able to build detailed maps of brain functions, such as the stereotactical method and apparatus, developed by British physiologist Victor Horsley. 7 REFERENCES AND BIBLIOGRAPHY:  Aboitiz F and Garcia GL. 1997. The evolutionary origin of language areas in the human brain. A neuroanatomical perspective. Brain Research Reviews 25:381-396.  Amunts K, Schleicher A, Bürgel U, Mohlberg H, Uylings HBM, and Zilles K. 1999. Broca's region revisited: Cytoarchitecture and intersubject variability. J Comp Neurol 412:319-341.  Amunts K, Weiss PH, Mohlberg H, Pieperhoff P, Gurd J, Marshall JC, Fink GR, and Zilles K. 2002.  Analysis of verbal fluency in microstructurally defined stereotactic space: The role of Brodmann's areas 44 and 45. Neuroimage 16:176.  Berker EA, Berker AH, and Smith A. 1986. Translation of Broca's 1865 report. Arch Neurol 43:1065-1072. 8
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