Visual — Spatial Functioning

Abstract

Visual-spatial functioning, as used in this book, is a general term referring to visuoperceptual, visuospatial, or visuoconstructive abilities. The visual system may be divided into a number of areas of functioning and anatomically separate subsystems. Visual object perception or pattern recognition involves the identification of spatial collections of visual qualities. Impairment is termed visual agnosia. The neuroanatomical substrate of object recognition appears to involve the posterior temporal or inferotemporal cortex (Benton, 1985; Ungerleider & Mishkin, 1982). Other forms of recognition include recognition of familiar faces (impairment is termed prosopagnosia) and recognition of unfamiliar faces. A review of the different varieties of visual agnosia may be found in Visual Agnosia (Farah, 1990). Visual synthesis is the ability to grasp the relationships between simultaneously presented stimuli and integrate them into a meaningful whole (Benton, 1985). Visuospatial abilities involve the localization of objects or the self in space. The neuroanatomical substrate of the ability to localize objects appears to involve the posterior parietal cortex (Benton, 1985; Ungerleider & Mishkin, 1982). Subcategories of visuospatial abilities include the ability to localize points in space and to judge direction, distance, and depth. Topographical orientation is the ability to find one’s way around in or to describe various environments, e.g., home, neighborhood, or city. Visuoconstructive ability or constructional praxis is the ability to put parts together to form a single object (Benton, 1985). Successful performance of this activity requires accurate perception of the parts and their spatial relationships and unimpaired organization and performance of the motor activities necessary to construct the object (Benton, 1985).