Abstract
The relevance of the thalamus to intelligent behavior, which is suggested by its cortical connections, and by a few impressive, if isolated instances of selective thalamic disease in man,1-3 has been difficult to verify experimentally. While it is true that deficits in problem solving have been observed in rats4-6 and cats7,8 with thalamic lesions, similar studies with monkeys have yielded negative results. Defective performance in delayed response tests in monkeys with bilateral lesions of the dorsomedial nucleus have been sought for particularly, because of the frontal connections of this nucleus, and the consistent impairment in delayed response which is produced by bilateral frontal lesions. However, Walker9 and Peters et al10 found no impairment in delayed response performance in monkeys with bilateral lesions of the dorsomedial nucleus, and Chow,11 likewise, was unable to induce defects in delayed response by combined lesions in the pulvinar