Agnosia
Agnosia is the inability to process sensory information. Often there is a loss of ability to recognize objects, persons, sounds, shapes, or smells while the specific sense is not defective nor is there any significant memory loss. It is usually associated with brain injury or neurological illness, particularly after damage to the occipitotemporal border, which is part of the ventral stream. Agnosia only affects a single modality, such as vision or hearing. More recently, a top-down interruption is considered to cause the disturbance of handling perceptual information.
Visual agnosia
The two main categories of visual agnosia are:Patient C.K. was born in 1961 in England and emigrated to Canada in 1980. In January of 1988, C.K. sustained a head injury from a motor vehicle accident while out for a jog. Following the accident, C.K. experienced many cognitive issues, mood swings, poor memory, and temper outbursts. C.K. also had motor weakness on the left side and a left homonymous hemianopia. He recovered well, retaining normal intelligence and normal visual acuity. He was able to complete a Masters in History, later working as a manager at a large corporation. Although his recovery was successful in other areas of cognition, C.K. still struggles to make sense of the visual world.