PowerPoint Presentation - Brain Areas from Brain Imaging


	Slide 2. Visual cortex is retintopically and functionally subdivided into multiple areas: purpose is to localize the retinotopic regions, and to assess function. Introduce colour issue. Compare both chromatic responses (say that they are separated subcortically). The extent of color processing is controversial in primate neurophysiology. There is controversy on the extent to which neurons are color vs achromatically sensitive, and their proportions. One of the limiting issues in color vision has been how to define the chromatic stimuli, particularly their contrasts, in ways that allow you to compare meaningfully between chromatic and achromatic responses.

	Another key issue is that most of the research assessing cortical specializations have been done on primates and the extent to which human visual areas are analogous to the primate areas is presently being determined. For example, even in primates the extent that MT is color sensitive is controversial. In terms of V4 and the ventral stream, primate color processing has been controversial through out the 1990s, with Zeki defending V4 as a primate color area, in the face of primate lesion evidence suggesting that V4 is not specialized for color. It is known from clinical studies that this is unlikely in human, but the links between human V4 and primate V4, and the extent to which there exist other human color areas is presently controversial. (Need Wandell, MT, Liu & Wandell). Hadjakani.