Distinctive features of unilateral spatial agnosia in right and left brain-damaged patients.

In order to study the distinctive features of unilateral spatial agnosia shown by right and left brain-damaged patients, a test of copying drawings with guiding landmarks was given to 83 control subjects and to 248 patients affected by right (n = 108) or left (n = 140) hemispheric damage. The test enabled us to obtain a quantitative assessment both of the lines omitted ('omissions') and of the lines wrongly traced ('errors') on the half page contralateral to the damaged hemisphere. Results showed that contralaterally to the hemispheric locus of lesion a clear-cut double dissociation can be found between right and left brain-damaged patients: the former showed a striking tendency to omit the lines lying on the left half of the sheet, whereas the latter tended mainly to trace faulty lines on the right half of the drawings.