Agnosia: is a failure of perception, or “to experience a failure of knowledge”. For some, they are not able to develop a rational percept; others are not able to access the knowledge to identify an object.
Cortical Pathways
The occipitotemporal pathway is for object perception and recognition. The occipitoparietal pathway is for spatial perception or determining where an object is. Typically, the parietal and periphery determine “where” and the temporal and fovea help to determine “what”.
Object Recognition
Apperceptive Agnosia: failure to recognize an object. One study tested people with apperceptive agonsia to see how well they are able to recognize an incomplete picture. Typically, they are not able to tell what they picture is until it is complete. Reseachers found that there is more of a deficit when the right hemisphere is damaged than the left hemisphere. Warrington also gave the Unusual Views Object Test to those with apperceptive agnosia and found that they are not able to recognize and object that is shown to them in an unusual view.
Associative Agnosia: have the correct information but are not able to access it. One study found that those with associative agnosia could point out an object when they were named but could not point out the object when asked if they were different.
Prosopagnosia: the inability to recognize faces. Not only can a damaged brain cause prosopagnosia, but genes also play a role in this. Two regions of the temporal lobe a activiated while looking at faces: the superior temporal sulcus and the inferotemporal gyrus.
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