Visual Perception Disorders

Damage to the parts of the brain that process visual information can lead to a variety of visual agnosias, depending on which area is damaged. Some people with agnosia have difficulty recognizing familiar faces or objects, others cannot distinguish color, and still others may not perceive movement. A related phenomenon is neglect, which results in inattention to one side of the body (and visual field), so that objects on that side are not noticed. There are many interesting case histories of such individuals, and studying both the site of damage and the particular loss of function can tell us a great deal about how the brain allows us to "see" the world. Such disorders also illustrate the principle that visual perception is somewhat modular, meaning that particular aspects of objects are processed by different brain areas.

To prepare for this Discussion:

• Review the information on vision, particularly the discussion on disorders of visual perception.

• Select one of the disorders covered in the book (object agnosia, prosopagnosia, color agnosia, movement agnosia, or neglect) to research in more detail. Locate a research report or other scientific article about this disorder in the Walden Library.

• For the disorder you selected, think about the symptoms and problems commonly experienced by people with the disorder and the impact of the disorder on areas of life including work, relationships, and leisure time. Also note the areas of the brain responsible for the disorder and specific behaviors the disorder affects.

With these thoughts in mind:

Summary of the symptoms of the disorder you chose. Include the brain area(s) responsible for the disorder, and common problems that people with such damage have. Explain what everyday life would be like for an individual with the disorder, including its impact on occupation, relationships, and leisure time. Be sure to include how the disorder might affect the person's behaviors and experiences in these settings.

This is some web sites

Visual Projections to the Cortex (Brain and Behavior, Figure 10.4)

http://www.sagepub.com/garrettbb2study/animations/10.4.htm

This sequence traces the route by which the eyes send information to the brain.

Visual Detection of Edges (Brain and Behavior, Figure 10.20)

http://www.sagepub.com/garrettbb2study/animations/10.20.htm

This sequence demonstrates how on-center/off-surround retinal ganglion cells respond to edges and how these responses affect simple cells in the primary visual cortex.