Behavioral Neuropsychology

Visual Spatial Disorders

Figure Caption: Lesion of this area of the right parietal lobe often results in spatial disorders.

Visual Spatial Disorders

Disorders of spatial processing range from basic visual sensory deficits that result in visual spatial errors to higher level processing of visual information that result in more abstract visual spatial disability. Basic visual sensory deficits that result in errors are usually classes as visual field defects, sensory neglect or visual object agnosia. Lesions of the occipital lobe and association areas of the parietal and temporal lobes are the usual causes of these deficits (See the Perceptual Disorders section). The patient who has these functions intact may still have deficits in spatial processing and these disabilities are those usually subsumes under the heading of visual-spatial disorders. Patients with lesions of the parietal lobe of the right hemisphere have the most pronounced spatial processing deficits.

Spatial Localization

Patients with visual spatial impairment have great difficulty localizing objects in two and three dimensional space. For example patients with spatial disorder cannot determine if a pattern of dots presented on a card are the same or different than another pattern. They have difficulty judging distance from themselves to objects in space. Stereopsis (binocular depth perception) is often impaired. They also have difficulty matching directional orientation of objects. For example, it is difficult for these patients to judge whether two lines on a page have the same angular orientation. These difficulties in judging direction and distance are maintained even when the information about the objects is presented by touch as well as vision.

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Topographical Disorientation

This refers to a variety of errors in forming spatial maps and using them to find your places or solve topographical problems (e.g., "Tell me how far it is from the hospital to city hall"). Patients may even have difficulty formulating the layout of familiar environments, such as the patients home. It is difficult to determine if the deficit represents a failure in recalling familiar environments or in using imagery as a processing tool to solve the topographical problem posed to the patient.

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Visual Spatial Construction

As a result of visual-spatial processing deficits, patients have difficulty with construction activities that require spatial abilities. These include drawing, both copying as well as drawing to verbal command, and assembling two and three dimensional objects. This latter ability is usually examined with block puzzles. However, the deficit extends to everyday activities that require assembling objects from basic elements, such as laying out a place-setting at the table, assembling furniture or drawing a map to one's house. Although patients with visual spatial impairment show impairment on these tasks, the activities all require substantial motor skill and praxis. Consequently, patients with lesions of other parts of the brain that subsume these functions will also have difficulty with spatial construction tasks.

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Assessment

Examination of visual-spatial ability is accomplished by asking the patient to draw simple figures, such as a flower, square or the face of a clock. Completing pencil-and-paper mazes also reveals visual spatial ability. Block puzzle tasks are also used to examine the patient's ability to form two- and three-dimensional constructions. Usually the patient is asked to reproduce a block shape shown in a picture or assembled by the examiner. Errors in route-finding and topographical orientation are assessed by self-report of the patient or by an interview of the patient's spouse or family. They will usually have a few stories about the patient's difficulties that clearly suggest the patient gets lost or cannot coordinate the body in space.

The line orientation test is also used to examine spatial reasoning. Here, the patient is asked to find a model line, presented at an angle, among a group of lines presented at different angles. One of the alternative lines is presented at the same angle as the model.

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