Visual processing

Not to be confused with image processing.

Visual processing is the sequence of steps that information takes as it flows from visual sensors to cognitive processing organs. The sensors may be zoological eyes or they may be cameras or sensor arrays that sense various portions of the electromagnetic spectrum.

Processing of face and place stimuli

Past models of visual processing have distinguished certain areas of the brain by the specific stimuli that they are most responsive to; for example, the parahippocampal place area (PPA) has been shown to have heightened activation when presented with buildings and place scenes (Epstein & Kanwisher, 1998), whereas the fusiform face area (FFA) responds mostly strongly to faces and face-like stimuli (Kanwisher et al., 1997).

Parahippocampal Place Area (PPA)

The parahippocampal place area (PPA) is located in the posterior parahippocampal gyrus, which itself is contained in the medial temporal lobe with close proximity to the hippocampus. Its name comes from the increased neural response in the PPA when viewing places, like buildings, houses, and other structures, and when viewing environmental scenes, both indoors and outdoors (Epstein & Kanwisher, 1998). This is not to say that the PPA does not show activation when presented with other visual stimuli – when presented with familiar objects that are neither buildings nor faces, like chairs, there is also some activation within the PPA (Ishai et al, 2000). It does however appear that the PPA is associated with visual processing of buildings and places, as patients who have experienced damage to the parahippocampal area demonstrate topographic disorientation, in other words, unable to navigate familiar and unfamiliar surroundings (Habib & Sirigu, 1987). Outside of visual processing, the parahippocampal gyrus is involved in both spatial memory and spatial navigation (Squire & Zola-Morgan, 1991).

Fusiform Face Area (FFA)

The fusiform face area is located within the inferior temporal cortex in the fusiform gyrus. Similar to the PPA, the FFA exhibits higher neural activation when visually processing faces more so than places or buildings (Kanwisher et al., 1997). However, the fusiform area also shows activation for other stimuli and can be trained to specialize in the visual processing of objects of expertise. Past studies have investigated the activation of the FFA in people with specialized visual training, like bird watchers or car experts who have adapted a visual skill in identifying traits of birds and cars respectively. It has been shown that these experts have developed FFA activation for their specific visual expertise. Other experiments have studied the ability to develop expertise in the FFA using ‘greebles’, a visual stimulus generated to have a few components that can be combined to make a series of different configurations, much like how a variety of slightly different facial features can be used to construct a unique face. Participants were trained on their ability to distinguish greebles by differing features and had activation in the FFA measured periodically through their learning – the results after training demonstrated that greeble activation in the FFA increased over time whereas FFA responses to faces actually decreased with increased greeble training. These results suggested three major findings in regards to FFA in visual processing: firstly, the FFA does not exclusively process faces; secondly, the FFA demonstrates activation for ‘expert’ visual tasks and can be trained over time to adapt to new visual stimuli; lastly, the FFA does not maintain constant levels of activation for all stimuli and instead seems to ‘share’ activation in such a way that the most frequently viewed stimuli receives the greatest activation in the FFA as seen in the greebles study (Gauthier et al., 2000).  

Development of the FFA and PPA in the brain

Some research suggests that the development of the FFA and the PPA is due to the specialization of certain visual tasks and their relation to other visual processing patterns in the brain. In particular, existing research shows that FFA activation falls within the area of the brain that processes the immediate field of vision, whereas PPA activation is located in areas of the brain that handle peripheral vision and vision just out of the direct field of vision (Levy et al.­­, 2001). This suggests that the FFA and PPA may have developed certain specializations due to the common visual tasks within those fields of view. Because faces are commonly processed in the immediate field of vision, the parts of the brain that process the direct field of vision eventually also specialize in more detailed tasks like face recognition. The same concept applies to place: because buildings and locations are often viewed in their entirety either right outside of the field of vision or in an individual’s periphery, any building or location visual specialization will be processed within the areas of the brain handling peripheral vision. As such, commonly seen shapes like houses and buildings become specialized in certain regions of the brain, i.e. the PPA.

See also

• Visual agnosia
• Visual cortex
• Visual perception
• Visual system

References

• Das M, Bennett DM, Dutton GN (November 2007). "Visual attention as an important visual function: an outline of manifestations, diagnosis and management of impaired visual attention". Br J Ophthalmol. 91 (11): 1556–60. doi:10.1136/bjo.2006.104844. PMC 2095436. PMID 17301124.
• Hellige JB (1996). "Hemispheric asymmetry for visual information processing". Acta Neurobiol Exp. 56 (1): 485–97. PMID 8787209.
• Kitahara K (March 2007). "[Physiology and pathology of visual information processing]". Nippon Ganka Gakkai Zasshi (in Japanese). 111 (3): 160–91, discussion 192. PMID 17402561.
• Miles FA (March 1998). "The neural processing of 3-D visual information: evidence from eye movements". Eur. J. Neurosci. 10 (3): 811–22. doi:10.1046/j.1460-9568.1998.00112.x. PMID 9753150.
• Vidyasagar TR (2005). "Attentional gating in primary visual cortex: a physiological basis for dyslexia". Perception. 34 (8): 903–11. doi:10.1068/p5332. PMID 16178142.
• Epstein, R., & Kanwisher N. (1998). A cortical representation of the local visual environment. In Nature (Vol 392, pp. 598-601).
• Gauthier, I., Skudlarski, P., Gore, J.C., & Anderson, A.W. (2000). Expertise for cars and birds recruits brain areas involved in face recognition. In Nature Neuroscience (Vol 3, pp. 191-197).
• Habib M. & Sirigu A. (1987). Pure topographical disorientation: a definition and anatomical basis. In Cortex (Vol 23, pp. 73-85).
• Ishai A., Ungerleider L.G., & Haxby J.V. (2000). Distributed neural systems for the generation of visual images. In Neuron (Vol 28, pp 979-990).
• Kanwisher N., McDermott J., & Chun MM. The fusiform face area: a module in human extrastriate cortex specialized for face perception. In Neurosci (Vol 17, pp 4302-4311).
• Levy, I., Hasson, U., Avidan, G., Hendler, T., & Malach, R. (2001). Center-periphery organization of human object areas. In Nature Neuroscience (Vol 4, pp. 533-539).
• Squire, L.R, Zola-Morgan, S. (1991). The medial temporal lobe memory system. In Science (Vol 253, pp. 1380-1386)