Chapter 2

Chapter 2 - Chapter 2 Biological Foundations of Sensory...

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Chapter 2 – Biological Foundations of Sensory Perception A. Organization of the Nervous System - 2 dominant themes have arisen from 18 th c. Austrian physician Gall’s proposition that all mental functions can be precisely localized to certain parts of the brain: o That the brain is a heterogeneous collection of functionally specialized structures/areas OR o The brain is a homogeneous organ in which the various functions are diffuse/ synergistic. - Phrenology : 1 st complete theory of cerebral localization (Gall); various mental faculties were believed to occupy discrete parts of brain’s surface, which produced bumps/depressions in skull. - Brain lesion studies in animals and study of clinical cases in humans w/ brain damage were the first efforts made to understand functional specialization. Clinical and experimental studies in the 19 th c.: - Paul Broca reintroduced interest in localization; studied the case of a patient (Tan) who had lost the ability to speak, a condition known as aphasia . Postmortem findings showed a lesion in the frontal part of the brain that was only present in the left hemisphere- known now as Broca’s area. - Carl Wernicke showed that a lesion in the posterior left hemisphere (Wernicke’s area) produced a different aphasia- inability to understand speech (ability to produce speech= Broca’s area). - Wernicke’s theory : simple sensory and motor functions are localized to discrete brain areas but that the interaction of these modules controls more complex behaviors, perceptions, and actions. Phineas Gage, 1848: metal rod through brain; rod spared the regions of his frontal lobe necessary for language but not those of the prefrontal cortex (social behavior) severe personality changes. Modern views on functional specialization: - Histology- the study of fine structure/ organization of tissue or organ at a microscopic level advances led to a better understanding of brain structures. - The first definitive studies in functional localization were conducted by Canadian neurosurgeon Wilder Penfield in the 1950s. o He used electrodes to stimulate brains of (awake) patients undergoing seizure surgery. o Confirmed lang. capabilities of Broca’s/Wernicke’s areas and other localization features. -
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This note was uploaded on 12/18/2011 for the course PSYC 212 taught by Professor Shahin during the Fall '11 term at McGill.

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Chapter 2 - Chapter 2 Biological Foundations of Sensory...

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