Block constructions of chronic alcoholic and unilateral brain-damaged patients: a test of the right hemisphere vulnerability hypothesis of alcoholism.

A detailed analysis of the block construction performance of chronic alcoholics, unilateral brain-damaged patients, and normal control subjects was conducted to test two hypotheses: (a) that alcoholics perform similarly to right-hemisphere damaged (RHD) patients but not left-hemisphere damaged (LHD) patients; and (b) that unilateral brain-damaged patients display qualitatively different strategies and errors. Differences in performance without a time limit and broken configuration errors suggest that the alcoholics have not incurred the type of visuospatial impairment characteristic of RHD patients. The LHD and RHD patients showed qualitative differences in their strategies and errors. Implications of the findings for research and clinical assessment of visuospatial dysfunction are discussed.

Visuospatial dysfunction following unilateral brain damage: dissociations in hierarchical and hemispatial analysis.

Unlike the aphasias, visuospatial dysfunction has resisted fractionation into meaningful spared and impaired component functions. In this study, we show that unilateral brain damage results in pronounced dissociations in both hierarchical and hemispatial processing. Patients with left-hemisphere damage showed the greatest impairment in drawing forms at the lower level of hierarchical stimuli presented in right hemispace, whereas patients with right-hemisphere compromise displayed the opposite pattern. We discuss implications of these results for research in visuospatial function and clinical assessment of visuospatial dysfunction.

Visuospatial functioning before and after commissurotomy. Disconnection in hierarchical processing.

A patient who underwent complete cerebral commissurotomy was tested before and after surgery on tasks involving drawing and recognition memory for visual hierarchical stimuli. These stimuli consisted of a large, higher-level form constructed from smaller, lower-level forms. Postoperatively, the patient was more accurate in drawing and recognizing higher-level forms relative to lower-level forms when responding with his left hand and primarily right hemisphere, whereas he showed the opposite pattern when responding with his right hand and primarily left hemisphere. Implications of these findings for theories of the cerebral organization of visuospatial processing are discussed.