Mechanisms of unilateral spatial neglect in relation to laterality of cerebral lesions.

An Overlapping Figures test, considered as appropriate to study focusing of attention on small but complex stimuli falling in the central parts of visual field and a Searching for Animals test, designed to study the exploration of large parts of extrapersonal space, were administered to 38 controls, and 90 right and 82 left brain-damaged patients. The investigation was designed to test the hypothesis that the extent of space to be explored may have a different influence on unilateral spatial neglect of right and left brain-damaged patients. Both right and left brain-damaged patients showed an asymmetric exploration of space on the Searching for Animals test, making more omissions on the side contralateral to the damaged hemisphere than on the ipsilateral one. On the Overlapping Figures test, however, only right brain-damaged patients showed a clear tendency to omit figures lying on the left side of the composite pattern. This finding suggests that inability to extract visual information from one side of the stimuli during single eye fixations may be the most characteristic feature of unilateral spatial neglect resulting from right hemisphere lesions.