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Abstract:
Both material-specific and set-specific regions were
identified in frontal cortex, using a two (material type: verbal,
nonverbal) by two (task: encoding, retrieval) within-subjects
design and fMRI. A region in the posterior and dorsal extent of
inferior frontal gyrus (BA 6/44), which has been shown to
demonstrate laterality effects in intentional encoding as a
function of material type (Kelley, et al. 1998), demonstrated
similar laterality effects during recognition memory: Words
produced predominantly left-lateralized activation, whereas
unfamiliar faces elicited predominantly right-lateralized
activations. No effect of the encoding/retrieval manipulation were
observed in this region. A region of right anterior prefrontal
cortex (BA10) has been activated in many memory retrieval studies
(e.g.,Buckner et al., 1996). Many, but not all, studies showing
this pattern have used verbal materials. We demonstrated that both
faces and words produced higher levels of activation in this region
during the retrieval task than during the encoding task. In
summary, two distinct regions of prefrontal cortex were dissociated
as a function of task demands: Right anterior prefrontal cortex was
sensitive to the ìsetî or intention of the
participants (i.e., was more active in retrieval than encoding),
and a region of inferior frontal gyrus was equivalently active in
encoding and retrieval but was sensitive to the materials
manipulation.
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