Visual Agnosia

The Nature of Visual Agnosia

In neuropsychology visual agnosia is the name of a general condition characterized by the inability to recognize visual stimuli despite normal low-level vision (e.g., normal color perception and normal visual field). Patients can show inability to recognize objects (object agnosia), colors (color agnosia) and/or faces (prosopagnosia) (Denes and Pizzamiglio, 1996).

Prosopagnosia describes a condition of face blindness. Patients can recognize other objects, but they can no longer recognize faces. Most people can recognize a face regardless of context.

One can recognize his or her father’s face, regardless of where one sees it. If the father’s face is in the newspaper, on the “fan-cam” at a sporting event, or in a family album, it can be recognized. A patient with prosopagnosia cannot do this. However, characteristics that are not facial in nature can help the patient recognize a familiar face. For example, if the patient’s spouse always wears a trademark hat, recognition can occur by noting the hat.

In summary, face memory seems to be an integrated process involving both areas in the occipital lobe, which we know are involved with the perception and recognition of faces, and areas in the temporal lobe, which we know are involved in recognizing complex objects and memory.

Damage to these areas results in a strange condition known as prosopanosia, which is a selective deficit at recognizing and remembering human faces. In most people, however, these areas are constantly being used as we negotiate our ways through the sea of human faces that surround us.