PET VALIDATION OF A NOVEL PREFRONTAL TASK - DELAYED-RESPONSE ALTERNATION

Deficits in working memory have been proposed to explain the performan ce failures of frontally lesioned primates on delayed alternation(DA) and delayed response (DR) tasks. The authors examined a computerized t est of delayed response alternation (DRA), which combines elements of DR and DA in a sample of 18 normal volunteers who underwent oxygen-15 PET regional cerebral blood flow scans during the DRA and a sensorimot or control task. Significant activations were observed in a network of frontal, parietal, occipital, and temporal regions during initial tas k performance. A qualitatively similar but somewhat reduced set of act ivations was observed in a subset of participants who repeated the tas k after practice and instruction. These results are consistent with di stributed models of working memory derived from studies of nonhuman pr imates and suggest that the frontal lobes contribute to human working memory function.