PSY 3400 W2 Assignment Visual Modularity
PSY 3400 W2 Assignment Visual Modularity
In cognitive neuroscience, visual modularity is an organizational concept concerning how vision works. The way in which the primate visual system operates is currently under intense scientific scrutiny. One dominant thesis is that different properties of the visual world (color, motion, form and so forth) require different computational solutions which are implemented in anatomically/functionally distinct regions that operate independently – that is, in a modular fashion.[1]
Motion processing
Akinetopsia, a term coined by Semir Zeki,[2] refers to an intriguing condition brought about by damage to the Extrastriate cortex MT+ that renders humans and monkeys unable to perceive motion, seeing the world in a series of static “frames” instead[3][4][5][6] and indicates that there might be a “motion centre” in the brain. Of course, such data can only indicate that this area is at least necessary to motion perception, not that it is sufficient; however, other evidence has shown the importance of this area to primate motion perception. Specifically, physiological, neuroimaging, perceptual, electrical- and transcranial magnetic stimulation evidence (Table 1) all come together on the area V5/hMT+. Converging evidence of this type is supportive of a module for motion processing. However, this view is likely to be incomplete: other areas are involved with motion perception, including V1,[7][8][9] V2 and V3a [10] and areas surrounding V5/hMT+ (Table 2).
A recent fMRI study put the number of motion areas at twenty-one.[11] Clearly, this constitutes a stream of diverse anatomical areas. The extent to which this is ‘pure’ is in question: with Akinetopsia come severe difficulties in obtaining structure from motion.[12] V5/hMT+ has since been implicated in this function[13] as well as determining depth.[14] Thus the current evidence suggests that motion processing occurs in a modular stream, although with a role in form and depth perception at higher levels.