Parietal hemineglect and motor deficits in the monkey.

To study the parietal hemineglect syndrome, we trained and operated nine Macaca fasicularis monkeys. Contralateral to the lesion they showed response abnormalities to visual and somatic sensory stimuli, and misreaching toward targets in visual space, abberant finger and wrist postures and lack of pincer grasp. The latter did not appear during performance of a preoperatively practised task, nor depend for severity upon lesion size, whereas sensory response abnormalities did. We conclude that abnormal motor patterns are separable from hemineglect in parietal animals, and are worst when the movement is directed to a visual target in extrapersonal space.