VISUAL HEMINEGLECT INDUCED BY UNILATERAL STRIATAL DOPAMINE DEFICIENCYIN MONKEYS

UNILATERAL dopamine deficiency of the basal ganglia produced a profoun d impairment of visual search. Dopaminergic innervation of the monkey striatum was deprived unilaterally by infusing 1-methyl-4-phenyl-1,2,3 ,6-tetrahydropyridine (MPTP) into the caudate nucleus. The monkeys wer e shown a mirror in which they saw their own image and surroundings. C ompared with the concentric and symmetrical distribution of visual sea rch before MPTP infusion, the gaze after MPTP infusion was confined an d sometimes frozen in peripheral regions in the hemispace ipsilateral to the infusion; the contralateral side was largely neglected. An expe riment using a choice saccade task indicated that the contralateral vi sual signal, which alone was processed normally, was suppressed by the ipsilateral signal.