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.
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 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, V2 and V3a  and areas surrounding V5/hMT+ (Table 2). A recent fMRI study put the number of motion areas at twenty-one. 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. V5/hMT+ has since been implicated in this function as well as determining depth. 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.
|Physiology (single cell recording)||Cells directionally and speed selective in MT/V5|||
|Neuroimaging||Greater activation for motion information than static information in V5/MT|||
|Electrical-stimulation & perceptual||Following electrical stimulation of V5/MT cells perceptual decisions are biased towards the stimulated neuron’s direction preference|||
|Magnetic-stimulation||Motion perception is also briefly impaired in humans by a strong magnetic pulse over the corresponding scalp region to hMT+|||
|Psychophysics||Perceptual asynchrony among motion, color and orientation.|||
|Physiology (single cell recording)||Complex motion involving contraction/expansion and rotation found to activate neurons in medial superior temporal area (MST)|||
|Neuroimaging||Biological motion activated superior temporal sulcus|||
|Neuroimaging||Tool use activated middle temporal gyrus and inferior temporal sulcus|||
|Neuropsychology||Damage to visual area V5 results in akinetopsia|||
Similar converging evidence suggests modularity for color. Beginning with Gowers’ finding that damage to the fusiform/lingual gyri in occipitotemporal cortex correlates with a loss in color perception (achromatopsia), the notion of a "color centre" in the primate brain has had growing support. Again, such clinical evidence only implies that this region is critical to color perception, and nothing more. Other evidence, however, including neuroimaging and physiology converges on V4 as necessary to color perception. A recent meta-analysis has also shown a specific lesion common to achromats corresponding to V4. From another direction altogether it has been found that when synaesthetes experience color by a non-visual stimulus, V4 is active. On the basis of this evidence it would seem that color processing is modular. However, as with motion processing it is likely that this conclusion is inaccurate. Other evidence shown in Table 3 implies different areas’ involvement with color. It may thus be more instructive to consider a multistage color processing stream from the retina through to cortical areas including at least V1, V2, V4, PITd and TEO. Consonant with motion perception, there appears to be a constellation of areas drawn upon for color perception. In addition, V4 may have a special, but not exclusive, role. For example, single cell recording has shown that only V4 cells respond to the color of a stimuli rather than its waveband, whereas other areas involved with color do not.
|Other areas involved with color/Other functions of V4||Source|
|Wavelength sensitive cells in V1 and V2|||
|anterior parts of the inferior temporal cortex|||
|posterior parts of the superior temporal sulcus (PITd)|||
|Area in or near TEO|||
|Link between vision, attention and cognition|||
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 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. Neuroimaging of intact individuals reveals strong occipito-temporal activation during object presentation and greater activation still for object recognition. 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 suggests activation in this area does underpin object recognition. Within these regions are more specialized areas for face or fine grained analysis, place perception and human body perception. 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  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.
One of the first uses of the term "module" or "modularity" occurs in the influential book "Modularity of Mind" by philosopher Jerry Fodor. 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." 
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) (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. In addition, although achromats experience other cognitive defects they do not have motion deficits when their lesion is restricted to V4, or total loss of form perception. 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. 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), the recent evidence that 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.
- Society of Mind which proposes the mind is made up of agents
- Two Streams hypothesis
- Calabretta,, R.; Parisi, D. (2005). "Evolutionary Connectionism and Mind/Brain Modularity". Modularity. Understanding the development and evolution of complex natural systems (Cambridge, MA: MIT Press) 361 (1467): 309–330. doi:10.1098/rstb.2005.1807. PMC 1609335. PMID 16524839.
- Zihl, J.; von Cramon, D.Y., Mai N., Schmid, C. (1991). "Disturbance of movement vision after bilateral posterior brain damage". Brain 114 (144): 2235–2252. doi:10.1093/brain/114.5.2235. PMID 1933243.
- Zihl, J.; von Cramon, D.Y., Mai, N. (1983). "Selective disturbances of movement vision after bilateral brain damage". Brain 106 (106): 313–340. doi:10.1093/brain/106.2.525-a.
- Hess, Baker, Zihl (1989). "The" motion-blind" patient: low-level spatial and temporal filters". Journal of Neuroscience 9 (5): 1628–1640. PMID 2723744.
- Baker, Hess, Zihl (1991). "Residual motion perception in a" motion-blind" patient, assessed with limited-lifetime random dot stimuli". Journal of Neuroscience 11 (2): 454–461. PMID 1992012.
- Orban, G.A.; Kennedy, H.; Bullier, J. (1986). "Velocity sensitivity and direction selectivity of neurons in areas V1 and V2 of the monkey: influence of eccentricity". Journal of Neurophysiology 56 (2): 462–480. doi:10.1016/j.jphysparis.2004.03.004. PMID 3760931.
- Movshon, J.A.; Newsome, W.T. (1996). "Visual response properties of striate cortical neurons projecting to area MT in macaque monkeys". Journal of Neuroscience 16 (23): 7733–7741. PMID 8922429.
- Born, R.T.; Bradley, D.C. (2005). "Structure and function of visual area MT". Annual Review of Neuroscience 28: 157–189. doi:10.1146/annurev.neuro.26.041002.131052. PMID 16022593.
- Grill-Spector, K.; Malach, R. (2004). "The Human Visual Cortex". Annual Review of Neuroscience 7: 649–677. doi:10.1146/annurev.neuro.27.070203.144220. PMID 15217346.
- Stiers, P; Peeters, R; Lagae, L; Van Hecke, P; Sunaert, S (Jan 1, 2006). "Mapping multiple visual areas in the human brain with a short fMRI sequence". NeuroImage 29 (1): 74–89. doi:10.1016/j.neuroimage.2005.07.033. PMID 16154766. Retrieved 28 April 2013.
- Rizzo, Matthew; Nawrot, Mark; Zihl, Josef (1 January 1995). "Motion and shape perception in cerebral akinetopsia". Brain 118 (5): 1105–1127. doi:10.1093/brain/118.5.1105. PMID 7496774.
- Grunewald, A; Bradley, DC; Andersen, RA (Jul 15, 2002). "Neural correlates of structure-from-motion perception in macaque V1 and MT". The Journal of neuroscience : the official journal of the Society for Neuroscience 22 (14): 6195–207. PMID 12122078.
- DeAngelis, GC; Cumming, BG; Newsome, WT (Aug 13, 1998). "Cortical area MT and the perception of stereoscopic depth". Nature 394 (6694): 677–80. doi:10.1038/29299. PMID 9716130.
- Zeki, SM (Feb 1974). "Functional organization of a visual area in the posterior bank of the superior temporal sulcus of the rhesus monkey". The Journal of physiology 236 (3): 549–73. PMC 1350849. PMID 4207129.
- Van Essen, D. C.; Maunsell, J. H. R.; Bixby, J. L. (1 July 1981). "The middle temporal visual area in the macaque: Myeloarchitecture, connections, functional properties and topographic organization". The Journal of Comparative Neurology 199 (3): 293–326. doi:10.1002/cne.901990302. PMID 7263951.
- Maunsell, JH; Van Essen, DC (May 1983). "Functional properties of neurons in middle temporal visual area of the macaque monkey. I. Selectivity for stimulus direction, speed, and orientation". Journal of neurophysiology 49 (5): 1127–47. PMID 6864242.
- Felleman, DJ; Kaas, JH (Sep 1984). "Receptive-field properties of neurons in middle temporal visual area (MT) of owl monkeys". Journal of neurophysiology 52 (3): 488–513. PMID 6481441.
- Culham, JC; Brandt, SA; Cavanagh, P; Kanwisher, NG; Dale, AM; Tootell, RB (Nov 1998). "Cortical fMRI activation produced by attentive tracking of moving targets". Journal of neurophysiology 80 (5): 2657–70. PMID 9819271.
- Salzman, CD; Murasugi, CM; Britten, KH; Newsome, WT (Jun 1992). "Microstimulation in visual area MT: effects on direction discrimination performance". The Journal of neuroscience : the official journal of the Society for Neuroscience 12 (6): 2331–55. PMID 1607944.
- Hotson, John; Braun, Doris; Herzberg, William; Boman, Duane (1994). "Transcranial magnetic stimulation of extrastriate cortex degrades human motion direction discrimination". Vision Research 34 (16): 2115–2123. doi:10.1016/0042-6989(94)90321-2. PMID 7941409.
- Beckers, G.; Zeki, S. (1 January 1995). "The consequences of inactivating areas V1 and V5 on visual motion perception". Brain 118 (1): 49–60. doi:10.1093/brain/118.1.49. PMID 7895014.
- Walsh, V; Cowey, A (Mar 1, 1998). "Magnetic stimulation studies of visual cognition". Trends in cognitive sciences 2 (3): 103–10. doi:10.1016/S1364-6613(98)01134-6. PMID 21227086.
- Moutoussis, K.; Zeki, S. (22 March 1997). "A direct demonstration of perceptual asynchrony in vision". Proceedings of the Royal Society B: Biological Sciences 264 (1380): 393–399. doi:10.1098/rspb.1997.0056. PMC 1688275. PMID 9107055.
- Viviani, Paolo; Aymoz, Christelle (1 October 2001). "Colour, form, and movement are not perceived simultaneously". Vision Research 41 (22): 2909–2918. doi:10.1016/S0042-6989(01)00160-2. PMID 11701183.
- Tanaka, K; Saito, H (Sep 1989). "Analysis of motion of the visual field by direction, expansion/contraction, and rotation cells clustered in the dorsal part of the medial superior temporal area of the macaque monkey". Journal of neurophysiology 62 (3): 626–41. PMID 2769351.
- Grossman, E; Donnelly, M; Price, R; Pickens, D; Morgan, V; Neighbor, G; Blake, R (Sep 2000). "Brain areas involved in perception of biological motion". Journal of Cognitive Neuroscience 12 (5): 711–20. doi:10.1162/089892900562417. PMID 11054914.
- Beauchamp, MS; Lee, KE; Haxby, JV; Martin, A (Oct 1, 2003). "FMRI responses to video and point-light displays of moving humans and manipulable objects". Journal of Cognitive Neuroscience 15 (7): 991–1001. doi:10.1162/089892903770007380. PMID 14614810.
- Gowers, W. (1888). A manual of diseases of the brain. J & A Churchill.
- Meadows, JC (Dec 1974). "Disturbed perception of colours associated with localized cerebral lesions". Brain : a journal of neurology 97 (4): 615–32. doi:10.1093/brain/97.1.615. PMID 4547992.
- Zeki, S. (1 January 1990). "Parallelism and Functional Specialization in Human Visual Cortex". Cold Spring Harbor Symposia on Quantitative Biology 55 (0): 651–661. doi:10.1101/SQB.1990.055.01.062.
- Grüsser and Landis (1991). Visual agnosias and other disturbances of visual perception and cognition. MacMillan. pp. 297–303.
- Bartels, A. & Zeki, S. (2005). "Brain dynamics during natural viewing conditions - a new guide for mapping connectivity in vivo". NeuroImage 24 (2): 339–349. doi:10.1016/j.neuroimage.2004.08.044. PMID 15627577. "no"
- Bartels, A. & Zeki, S. (2000). "The architecture of the colour centre in the human visual brain: new results and a review". European Journal of Neuroscience 12 (1): 172–193. doi:10.1046/j.1460-9568.2000.00905.x. PMID 10651872. "no"
- Wachtler, T; Sejnowski, TJ; Albright, TD (Feb 20, 2003). "Representation of color stimuli in awake macaque primary visual cortex". Neuron 37 (4): 681–91. doi:10.1016/S0896-6273(03)00035-7. PMC 2948212. PMID 12597864.
- Kusunoki, M; Moutoussis, K; Zeki, S (May 2006). "Effect of background colors on the tuning of color-selective cells in monkey area V4". Journal of neurophysiology 95 (5): 3047–59. doi:10.1152/jn.00597.2005. PMID 16617176.
- Bouvier, S. E.; Engel, SA (27 April 2005). "Behavioral Deficits and Cortical Damage Loci in Cerebral Achromatopsia". Cerebral Cortex 16 (2): 183–191. doi:10.1093/cercor/bhi096. PMID 15858161.
- Rich, AN; Williams, MA; Puce, A; Syngeniotis, A; Howard, MA; McGlone, F; Mattingley, JB (2006). "Neural correlates of imagined and synaesthetic colours". Neuropsychologia 44 (14): 2918–25. doi:10.1016/j.neuropsychologia.2006.06.024. PMID 16901521.
- Sperling, JM; Prvulovic, D; Linden, DE; Singer, W; Stirn, A (Feb 2006). "Neuronal correlates of colour-graphemic synaesthesia: a fMRI study". Cortex; a journal devoted to the study of the nervous system and behavior 42 (2): 295–303. doi:10.1016/S0010-9452(08)70355-1. PMID 16683504.
- Livingstone, MS; Hubel, DH (Jan 1984). "Anatomy and physiology of a color system in the primate visual cortex". The Journal of neuroscience : the official journal of the Society for Neuroscience 4 (1): 309–56. PMID 6198495.
- DeYoe, EA; Van Essen, DC (Sep 5–11, 1985). "Segregation of efferent connections and receptive field properties in visual area V2 of the macaque". Nature 317 (6032): 58–61. doi:10.1038/317058a0. PMID 2412132.
- Zeki, S; Marini, L (1998). "Three cortical stages of colour processing in the human brain". Brain 121 (9): 1669–1685. doi:10.1093/brain/121.9.1669. PMID 9762956.
- Beauchamp, MS; Haxby, JV; Rosen, AC; DeYoe, EA (2000). "A functional MRI case study of acquired cerebral dyschromatopsia". Neuropsychologia 38 (8): 1170–9. doi:10.1016/S0028-3932(00)00017-8. PMID 10838151.
- Conway, B. R.; Tsao, DY (22 December 2005). "Color Architecture in Alert Macaque Cortex Revealed by fMRI". Cerebral Cortex 16 (11): 1604–1613. doi:10.1093/cercor/bhj099. PMID 16400160.
- Tootell, R. B.H.; Nelissen, K; Vanduffel, W; Orban, GA (1 April 2004). "Search for Color 'Center(s)' in Macaque Visual Cortex". Cerebral Cortex 14 (4): 353–363. doi:10.1093/cercor/bhh001. PMID 15028640.
- Pasupathy, A (2006). "Neural basis of shape representation in the primate brain". Progress in brain research. Progress in Brain Research 154: 293–313. doi:10.1016/S0079-6123(06)54016-6. ISBN 9780444529664. PMID 17010719.
- David, SV; Hayden, BY; Gallant, JL (Dec 2006). "Spectral receptive field properties explain shape selectivity in area V4". Journal of neurophysiology 96 (6): 3492–505. doi:10.1152/jn.00575.2006. PMID 16987926.
- Chelazzi, L; Miller, EK; Duncan, J; Desimone, R (Aug 2001). "Responses of neurons in macaque area V4 during memory-guided visual search". Cerebral cortex (New York, N.Y. : 1991) 11 (8): 761–72. doi:10.1093/cercor/11.8.761. PMID 11459766.
- Mishkin, Mortimer; Ungerleider, Leslie G.; Macko, Kathleen A. (1983). "Object vision and spatial vision: two cortical pathways". Trends in Neurosciences 6: 414–417. doi:10.1016/0166-2236(83)90190-X.
- Steeves, Jennifer K.E.; Culham, Jody C.; Duchaine, Bradley C.; Pratesi, Cristiana Cavina; Valyear, Kenneth F.; Schindler, Igor; Humphrey, G. Keith; Milner, A. David; Goodale, Melvyn A. (2006). "The fusiform face area is not sufficient for face recognition: Evidence from a patient with dense prosopagnosia and no occipital face area". Neuropsychologia 44 (4): 594–609. doi:10.1016/j.neuropsychologia.2005.06.013. PMID 16125741.
- Grill-Spector, Kalanit; Ungerleider, Leslie G.; Macko, Kathleen A. (2003). "The neural basis of object perception". Current Opinion in Neurobiology 13 (3): 399. doi:10.1016/S0959-4388(03)00060-6.
- Sheinberg, DL; Logothetis, NK (Feb 15, 2001). "Noticing familiar objects in real world scenes: the role of temporal cortical neurons in natural vision". The Journal of neuroscience : the official journal of the Society for Neuroscience 21 (4): 1340–50. PMID 11160405.
- Gauthier, I; Skudlarski, P; Gore, JC; Anderson, AW (Feb 2000). "Expertise for cars and birds recruits brain areas involved in face recognition". Nature Neuroscience 3 (2): 191–7. doi:10.1038/72140. PMID 10649576.
- Epstein, R; Kanwisher, N (Apr 9, 1998). "A cortical representation of the local visual environment". Nature 392 (6676): 598–601. doi:10.1038/33402. PMID 9560155.
- Downing, PE; Jiang, Y; Shuman, M; Kanwisher, N (Sep 28, 2001). "A cortical area selective for visual processing of the human body". Science 293 (5539): 2470–3. doi:10.1126/science.1063414. PMID 11577239.
- Fodor, Jerry A. (1989). The modularity of mind : an essay on faculty psychology (6. printing. ed.). Cambridge, Mass. [ u.a.]: MIT Press. ISBN 0-262-56025-9.
- Pylyshyn, Z (Jun 1999). "Is vision continuous with cognition? The case for cognitive impenetrability of visual perception". The Behavioral and brain sciences 22 (3): 341–65; discussion 366–423. doi:10.1017/s0140525x99002022. PMID 11301517.
- Leventhal, AG; Thompson, KG; Liu, D; Zhou, Y; Ault, SJ (Mar 1995). "Concomitant sensitivity to orientation, direction, and color of cells in layers 2, 3, and 4 of monkey striate cortex". The Journal of neuroscience : the official journal of the Society for Neuroscience 15 (3 Pt 1): 1808–18. PMID 7891136.
- Gegenfurtner, Karl R. (2003). "Sensory systems: Cortical mechanisms of colour vision". Nature Reviews Neuroscience 4 (7): 563–572. doi:10.1038/nrn1138. PMID 12838331.