“…As first demonstrated by Blum (1952), an equally disabling deficit on delayed-response tasks can be produced by more focal lesions of just the "midlateral" portion of the PFC. In fact, small circumscribed lesions of just the principal sulcus (i.e., areas 46 and 9/46d) can produce deficits as great as larger total prefrontal lesions (Butters & Pandya, 1969;Butters, Pandya, Stein, & Rosen, 1972;Goldman & Rosvold, 1970;Goldman, Rosvold, Vest, & Galkin, 1971;Gross & Weiskrantz, 1962;Mishkin, 1957). Lesions of the periacuate (i.e., areas 8Ad and 8Av), superior frontal (i.e., areas 8B and 9), orbital (i.e., areas 11 and 12), premotor (i.e., areas 6, 8, and 44), inferior temporal, and parietal cortex do not typically cause significant or long-lasting impaired delayed-response performance (Butters & Pandya, 1969;Goldman & Rosvold, 1970;Goldman et al, 1971;Jacobsen, 1936; Rosenkilde, The delayed matching-to-sample task (middle) is a nonspatial working memory task and requires the monkey to remember an object over a delay.…”