Visual modularity: Difference between revisions

Revision as of 23:22, 17 June 2017

Revision as of 22:32, 5 October 2017

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==Motion processing==

[[Akinetopsia]] is 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<ref name="zihl1">{{cite journal|vauthors=Zihl J, von Cramon D, Mai N, Schmid C |year=1991|title=Disturbance of movement vision after bilateral posterior brain damage|journal=Brain|issue=144|doi=10.1093/brain/114.5.2235|pages=2235–2252|volume=114|pmid=1933243}}</ref><ref name="zihl2">{{cite journal|last=Zihl|first=J. |author2=von Cramon, D.Y. |author3=Mai, N.|year=1983|title=Selective disturbances of movement vision after bilateral brain damage|journal=Brain|issue=2|doi=10.1093/brain/106.2.525-a|pages=313–340|volume=106}}</ref><ref name=Hess1989>{{cite journal |vauthors=Hess RH, Baker CL, Zihl J |title=The "motion-blind" patient: low-level spatial and temporal filters |journal=J. Neurosci. |volume=9 |issue=5 |pages=1628–40 |year=1989 |pmid=2723744 |doi= |url=}}</ref><ref name=Baker1991>{{cite journal | title=Residual motion perception in a" motion-blind" patient, assessed with limited-lifetime random dot stimuli | vauthors=Baker CL, Hess RF, Zihl J | journal=Journal of Neuroscience | year=1991 | volume=11 | issue=2 | pages=454–461 | pmid=1992012}}</ref> 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,<ref name="orban1">{{cite journal|last=Orban|first=G.A.|author2=Kennedy, H. |author3=Bullier, J. |year=1986|title=Velocity sensitivity and direction selectivity of neurons in areas V1 and V2 of the monkey: influence of eccentricity|journal=Journal of Neurophysiology|volume=56|issue=2|doi=10.1016/j.jphysparis.2004.03.004|pages=462–480|pmid=3760931}}</ref><ref name="mov1">{{cite journal|last=Movshon|first=J.A.|author2=Newsome, W.T. |year=1996|title=Visual response properties of striate cortical neurons projecting to area MT in macaque monkeys|journal=Journal of Neuroscience|volume=16|issue=23|pages=7733–7741|pmid=8922429}}</ref><ref>{{cite journal|last=Born|first=R.T.|author2=Bradley, D.C. |year=2005|title=Structure and function of visual area MT|journal=Annual Review of Neuroscience|volume=28|pages=157–189|pmid=16022593|doi=10.1146/annurev.neuro.26.041002.131052}}</ref> V2 and V3a <ref>{{cite journal|last=Grill-Spector|first=K.|author2=Malach, R. |year=2004|title=The Human Visual Cortex|journal=Annual Review of Neuroscience|volume=27|pages=649–677|doi=10.1146/annurev.neuro.27.070203.144220|pmid=15217346}}</ref> and areas surrounding V5/hMT+ (Table 2). A recent fMRI study put the number of motion areas at twenty-one.<ref name="stiers">{{cite journal|vauthors=Stiers P, Peeters R, Lagae L, Van Hecke P, Sunaert S |title=Mapping multiple visual areas in the human brain with a short fMRI sequence|journal=NeuroImage|date=Jan 1, 2006|volume=29|issue=1|pages=74–89|doi=10.1016/j.neuroimage.2005.07.033|pmid=16154766|url=http://www.sciencedirect.com/science/article/pii/S1053811905005070|accessdate=28 April 2013}}</ref> 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.<ref name=rizzo>{{cite journal|last=Rizzo|first=Matthew|author2=Nawrot, Mark |author3=Zihl, Josef |title=Motion and shape perception in cerebral akinetopsia|journal=Brain|date=1 January 1995|volume=118|issue=5|pages=1105–1127|doi=10.1093/brain/118.5.1105|pmid=7496774}}</ref> [[V5/hMT+]] has since been implicated in this function<ref name=grunewald>{{cite journal|last=Grunewald|first=A|author2=Bradley, DC |author3=Andersen, RA |title=Neural correlates of structure-from-motion perception in macaque V1 and MT|journal=The Journal of neuroscience : the official journal of the Society for Neuroscience|date=Jul 15, 2002|volume=22|issue=14|pages=6195–207|pmid=12122078}}</ref> as well as determining depth.<ref name=angelis>{{cite journal|last=DeAngelis|first=GC|author2=Cumming, BG |author3=Newsome, WT |title=Cortical area MT and the perception of stereoscopic depth|journal=Nature|date=Aug 13, 1998|volume=394|issue=6694|pages=677–80|doi=10.1038/29299|pmid=9716130}}</ref> 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.

{| class="wikitable"

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| Electrical-stimulation & perceptual

| Following electrical stimulation of V5/MT cells perceptual decisions are biased towards the stimulated neuron’s direction preference

| <ref name=salzman>{{cite journal|last=Salzman|first=CD|author2=Murasugi, CM |author3=Britten, KH |author4= Newsome, WT |title=Microstimulation in visual area MT: effects on direction discrimination performance|journal=The Journal of neuroscience : the official journal of the Society for Neuroscience|date=Jun 1992|volume=12|issue=6|pages=2331–55|pmid=1607944}}</ref>

|-

| [[Magnetic]]-stimulation

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|-

| [[Wavelength]] sensitive cells in V1 and V2

| <ref name=livingstone>{{cite journal|last=Livingstone|first=MS|author2=Hubel, DH |title=Anatomy and physiology of a color system in the primate visual cortex|journal=The Journal of neuroscience : the official journal of the Society for Neuroscience|date=Jan 1984|volume=4|issue=1|pages=309–56|pmid=6198495}}</ref><ref name=deyoe>{{cite journal|last=DeYoe|first=EA|author2=Van Essen, DC|title=Segregation of efferent connections and receptive field properties in visual area V2 of the macaque|journal=Nature|date=Sep 5–11, 1985|volume=317|issue=6032|pages=58–61|doi=10.1038/317058a0|pmid=2412132}}</ref>

|-

| anterior parts of the inferior temporal cortex

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== Form processing ==

Another clinical case that would a priori suggest a module for modularity in visual processing is visual [[agnosia]]. The well studied patient DF is unable to recognize or discriminate objects<ref name=mishkin>{{cite journal|last=Mishkin|first=Mortimer|author2=Ungerleider, Leslie G. |author3=Macko, Kathleen A. |title=Object vision and spatial vision: two cortical pathways|journal=Trends in Neurosciences|year=1983|volume=6|pages=414–417|doi=10.1016/0166-2236(83)90190-X}}</ref> owing to damage in areas of the lateral occipital cortex although she can see scenes without problem – she can literally see the forest but not the trees.<ref name=steeves>{{cite journal|last=Steeves|first=Jennifer K.E.|author2=Culham, Jody C. |author3=Duchaine, Bradley C. |author4=Pratesi, Cristiana Cavina |author5=Valyear, Kenneth F. |author6=Schindler, Igor |author7=Humphrey, G. Keith |author8=Milner, A. David |author9= Goodale, Melvyn A. |title=The fusiform face area is not sufficient for face recognition: Evidence from a patient with dense prosopagnosia and no occipital face area|journal=Neuropsychologia|year=2006|volume=44|issue=4|pages=594–609|doi=10.1016/j.neuropsychologia.2005.06.013|pmid=16125741}}</ref> [[Neuroimaging]] of intact individuals reveals strong occipito-temporal activation during object presentation and greater activation still for object recognition.<ref name=grillspector>{{cite journal|last=Grill-Spector|first=Kalanit|author2=Ungerleider, Leslie G. |author3=Macko, Kathleen A. |title=The neural basis of object perception|journal=Current Opinion in Neurobiology|year=2003|volume=13|issue=3|pages=399|doi=10.1016/S0959-4388(03)00060-6}}</ref> Of course, such activation could be due to other processes, such as visual attention. However, other evidence that shows a tight coupling of [[perceptual]] and [[physiological]] changes<ref name=sheinberg>{{cite journal|last=Sheinberg|first=DL|author2=Logothetis, NK |title=Noticing familiar objects in real world scenes: the role of temporal cortical neurons in natural vision|journal=The Journal of neuroscience : the official journal of the Society for Neuroscience|date=Feb 15, 2001|volume=21|issue=4|pages=1340–50|pmid=11160405}}</ref> suggests activation in this area does underpin object recognition. Within these regions are more specialized areas for face or fine grained analysis,<ref name=gauthier>{{cite journal|last=Gauthier|first=I|author2=Skudlarski, P |author3=Gore, JC |author4= Anderson, AW |title=Expertise for cars and birds recruits brain areas involved in face recognition|journal=Nature Neuroscience|date=Feb 2000|volume=3|issue=2|pages=191–7|doi=10.1038/72140|pmid=10649576}}</ref> place perception<ref name=epstein>{{cite journal|last=Epstein|first=R|author2=Kanwisher, N |title=A cortical representation of the local visual environment|journal=Nature|date=Apr 9, 1998|volume=392|issue=6676|pages=598–601|doi=10.1038/33402|pmid=9560155}}</ref> and human body perception.<ref name=downing>{{cite journal|last=Downing|first=PE|author2=Jiang, Y |author3=Shuman, M |author4= Kanwisher, N |title=A cortical area selective for visual processing of the human body|journal=Science|date=Sep 28, 2001|volume=293|issue=5539|pages=2470–3|doi=10.1126/science.1063414|pmid=11577239}}</ref> Perhaps some of the strongest evidence for the modular nature of these processing systems is the [[double dissociation]] between object- and face (prosop-) agnosia. However, as with color and motion, early areas (see <ref name=pasupathy/> for a comprehensive review) are implicated too, lending support to the idea of a multistage stream terminating in the inferotemporal cortex rather than an isolated module.

== Functional modularity ==

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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 : the official journal of the Society for 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 transactions of the Royal Society of London. Series B, Biological sciences|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==