Visual modularity: Difference between revisions

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One of the first uses of the term "module" or "modularity" occurs in the influential book "[[Modularity of Mind]]" by philosopher [[Jerry Fodor]].<ref name=fodor>{{cite book|last=Fodor|first=Jerry A.|title=The modularity of mind : an essay on faculty psychology|year=1989|publisher=MIT Press|___location=Cambridge, Mass. [ u.a.]|isbn=0-262-56025-9|edition=6. printing.}}</ref> A detailed application of this idea to the case of vision was published by Pylyshyn (1999), who argued that there is a significant part of vision that is not responsive to beliefs and is "cognitively impenetrable".<ref name=pylyshyn>{{cite journal|last=Pylyshyn|first=Z|title=Is vision continuous with cognition? The case for cognitive impenetrability of visual perception|journal=The Behavioral and Brain Sciences|date=Jun 1999|volume=22|issue=3|pages=341–65; discussion 366–423|pmid=11301517|doi=10.1017/s0140525x99002022}}</ref>

Much of the confusion concerning modularity exists in neuroscience because there is evidence for specific areas (e.g. V4 or V5/hMT+) and the concomitant behavioral deficits following brain insult (thus taken as evidence for modularity). In addition, evidence shows other areas are involved and that these areas subserve processing of multiple properties (e.g. V1<ref name=leventhal>{{cite journal|last=Leventhal|first=AG|author2=Thompson, KG |author3=Liu, D |author4=Zhou, Y |author5= Ault, SJ |title=Concomitant sensitivity to orientation, direction, and color of cells in layers 2, 3, and 4 of monkey striate cortex|journal=The Journal of Neuroscience|date=Mar 1995|volume=15|issue=3 Pt 1|pages=1808–18|pmid=7891136}}</ref>) (thus taken as evidence against modularity). That these streams have the same implementation in early visual areas, like V1, is not inconsistent with a modular viewpoint: to adopt the canonical analogy in cognition, it is possible for different software to run on the same hardware. A consideration of [[psychophysics]] and neuropsychological data would suggest support for this. For example, psychophysics has shown that percepts for different properties are realized asynchronously.<ref name=moutoussis1/><ref name=viviani/> In addition, although achromats experience other cognitive defects<ref name=gegenfurtner>{{cite journal|last=Gegenfurtner|first=Karl R.|title=Sensory systems: Cortical mechanisms of colour vision|journal=Nature Reviews Neuroscience|year=2003|volume=4|issue=7|pages=563–572|doi=10.1038/nrn1138|pmid=12838331}}</ref> they do not have motion deficits when their lesion is restricted to V4, or total loss of form perception.<ref name=zeki3>{{cite journal|last=Zeki|first=S|title=The Ferrier Lecture 1995 behind the seen: the functional specialization of the brain in space and time|journal=Philosophical transactionsTransactions of the Royal Society of London. Series B, Biological sciencesSciences|date=Jun 29, 2005|volume=360|issue=1458|pages=1145–83|doi=10.1098/rstb.2005.1666|pmid=16147515|pmc=1609195}}</ref> Relatedly, Zihl and colleagues' [[akinetopsia]] patient shows no deficit to color or object perception (although deriving depth and structure from motion is problematic, see above) and object agnostics do not have damaged motion or color perception, making the three disorders triply [[dissociable]].<ref name="zihl2"/> Taken together this evidence suggests that even though distinct properties may employ the same early visual areas they are functionally independent. Furthermore, that the intensity of subjective perceptual experience (e.g. color) correlates with activity in these specific areas (e.g. V4),<ref name="barzek2"/> the recent evidence that [[synesthesia|synaesthetes]] show V4 activation during the perceptual experience of color, as well as the fact that damage to these areas results in concomitant behavioral deficits (the processing may be occurring but perceivers do not have access to the information) are all evidence for visual modularity.

==See also==