[top of page 10 of handout]FOR functional localization:
“Thus our present-day knowledge of the organization of the visual cortex goes some way to support theories of cortical localization of function which the early neurologists fought so hard to establish.” (Zeki, 1978)
“manifestations differ according to the site of the
lesion..... such topographical associations come about
because particular parts of the brain were already required
for some lower function, which played a part in the
evolution of one of the many aspects of the use of language”
in analogy to the motor cortex, the posterior parietal cortex is formed by a multiplicity of areas, each of which is involved in the analysis of particular aspects of sensory information. There are no such things as multipurpose areas for space or body schema and (d) the parietofrontal connections form a series of segregated anatomical circuits devoted to specific sensorimotor transformations. (Rizzolatti et al, 1998)
Work of the past decade attests that the single neuron approach to perception and cognition has been profoundly successful. (Albright, Kandel and Posner, 2000: p. 621)
Determining the local circuit organization of the cerebral cortex and how that organization relates to the processing of region-specific information is, however, dauntingly complex, and its elucidation — important though it may be — is among the most formidable challenges facing cognitive neuroscience in the next decade.
…..the field will continue to advance through a global circuit-based approach to cognitive representation by the brain. (Albright, Kandel and Posner, 2000: pp.620-621).
[bottom of page 10 of handout]AGAINST functional localization
“..all of the cells of the brain, are participating, by a sort of algebraic summation, in every activity. There are no special cells for special memories.” (Lashley, 1950).
“Dissociation of functions, as in isolated loss of colour vision.... are less clearly referable to injury in any specific region.” (Lashley, 1948).
“It is not possible to demonstrate the isolated localization of a memory trace anywhere within the nervous system. Limited regions may be essential for learning or retention of a particular activity, but withing such regions the parts are functionally equivalent. The engram is represented throughout the region” (Lashley, 1950, p478)
Results are used to argue against innate localization of linguistic representations, and in favor of an alternative view in which innate regional biases in style of information processing lead to familiar patterns of brain organization for language under normal conditions and permit alternative patterns to emerge in children with focal brain injury. (Bates et al, 1997)
[bottom of page 10 of handout]A Compromise
“Another common source of confusion is the idea that distributed representation are somehow in conflict with the extensive evidence for localization of function in the brain (Luria, 1973). A system that uses distributed representation still requires many different modules for representing completely different kinds of thing at the same time. The distributed representations occur within the localized modules. For example, different modules would be devoted to things as different as mental images and sentence structures, but two different mental images would correspond to alternative patterns of activity in the same module. The representations advocated here are local at a global scale and global at a local scale.” (Hinton et al; 1986 vol 2, p. 79).
…..the field will continue to advance through a global circuit-based approach to cognitive representation by the brain. (Albright, Kandel and Posner, 2000: p621).
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