Differential functional connectivity of prefrontal and medial temporal cortices during episodic memory retrieval.

Some theories of brain function emphasize the interactions between brain areas as the major determinant of cognitive and behavioral operations. We explored such interactions in a PET study of episodic memory retrieval having three retrieval conditions, with differing levels of retrieval success. Functional connectivity of voxels located within Brodmann areas 10 and 45/47 in the right prefrontal cortex (RPFC) and the left hippocampus (LGH) with the rest of the brain was estimated using partial least squares. Area 10 and LGH showed an opposite pattern of functional connectivity, with a large expanse of bilateral limbic cortices that was equivalent in all tasks. However, during high retrieval, area 45/47 was included in this pattern. The results suggest that activity in portions of the RPFC reflects either memory retrieval mode or retrieval success, depending on other brain regions to which it is functionally linked. Copyright (c) 1997 Wiley-Liss, Inc.