Prosopagnosia

Prosopagnosia

What if you saw your friends but couldn’t recognize them. Or a picture of you and your family, and you just couldn’t distinguish your own face from the rest of the group. Despite the complexity of human faces as visual stimuli, most people rapidly and unthinkingly identify the faces of our family and friends. Since we do this with such a remarkable efficiency in this computationally formidable task, research suggests that our visual perceptual system employs a specific mechanism dedicated to processing facial identity. Evidence for the existence of such a mechanism comes from a disorder called prosopagnosia, or “face blindness,”, which is a selective and often severe deficit in the ability to recognize others’ faces. People suffering from the disorder are often unable to recognize their friends and family members by face alone, instead relying on vocal cues for proper identification. They cannot name images of celebrities, even if they can describe who the celebrity is.

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People with this disorder often describe faces as nearly indistinguishable; often as “strangely flat, white with emphatic dark eyes, as if made from a flat surface, like white, oval plates, all alike.” However, their general memory, visual ability and recognition of non-face objects often remains intact. They may properly judge facial expression, gender, and age, they often perform similarly to typical subjects on judgments of the trustwor­thiness or attractiveness of a face. They may also be able to detect a face-like pattern from a superficially meaningless visual array (pareidolia), and they can tell when an object is or is not a face.

This suggests that different com­ponents of face perception are disso­ciable and that prosopagnosia primarily involves a deficit specific to the process­ing of facial identity; more specifically from damage to the occipital and/or ventral temporal lobe, often including the fusi­form face area or occipital face area. Given the crucial social relevance of face recognition, it is unsurprising that evolution may have equipped humans with a neural mecha­nism dedicated to this task.

Several functional magnetic resonance imaging (fMRI) studies have examined activation in the fusiform face area in the fusiform gyrus during face perception, as this brain region is known to respond much more strongly to faces than other objects and scrambled images in normal subjects. In 2010, Stanford neuroscientists Kalanit Grill-Spector and Kevin Weiner discovered two nerve clusters in the fusiform gyrus — dubbed pFus and mFus — that respond more strongly to faces than they do to inanimate objects or other body parts. By building on these findings, they’ve offered some of the most compelling evidence to date of the fusiform’s role in facial recognition.

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Based on an article in the Journal of Neuroscience, researchers show that mild electrical stimulation of pFus and mFus caused a test subject’s perception of faces to be instantly distorted., he was experiencing instant prosopagnosia. Watch the interesting video at the bottom of this article:

http://io9.com/5953993/what-makes-us-see-jesus-in-a-taco-or-a-human-face-on-mars

The academic article can be found here:

Electrical Stimulation of Human Fusiform Face-Selective Regions Distorts Face Perception

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This entry was posted in Diplopi, Face perception, Neuroscience, Pareidolia, Perception and tagged , , , , . Bookmark the permalink.

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