27. Prefrontal systems underlying spontaneous and directed strategic processing during verbal learning

Prefrontal cortex supports strategic memory processes, including the ability to use semantic organizational strategies in novel or ambiguous learning situations. We used PET and a verbal learning paradigm to evaluate neural systems supporting spontaneous and directed use of semantic organizational strategies. There were three encoding conditions (Spontaneous, Di-rected, Unrelated) and behavioral measures of semantic clustering. In graded PET contrasts (D > S > U), two activations were found in left inferior prefrontal cortex (IPFC) and left dorsolateral prefrontal cortex (DLPFC). Covariate analyses indicated that blood flow in orbitofrontal cortex (OFC) was strongly correlated with spontaneous use of semantic clustering strategies during free recall. Findings indicate that OFC plays an important, and previously unappreciated, role in strategic memory by supporting early mobilization of behavioral strategies in novel or ambiguous situations.