Set- and code-specific activation in the frontal cortex: An fMRI study of encoding and retrieval of faces and words

The frontal cortex has been described as playing both "set-specific" and "c ode-specific" roles in human memory processing. Set specificity refers to t he finding of goal-oriented differences in activation patterns (e.g., encod ing relative to retrieval). Code specificity refers to the finding of diffe rent patterns of activation for different types of stimuli (e.g., verbal/no nverbal). Using a two (code: verbal, nonverbal) by two (set: encoding, retr ieval) within-subjects design and fMRI, we explored the influence of type o f code and mental set in two regions in the frontal cortex that have been p reviously shown to be involved in memory. A region in the dorsal extent of the inferior frontal gyrus (BA 6/44) demonstrated code-specific effects. Sp ecifically, an interaction of material type with hemisphere was obtained, s uch that words produced predominantly left-lateralized activation, whereas unfamiliar faces elicited predominantly right-lateralized activation. A reg ion of the right frontal polar cortex tin or near BA 10), which has been ac tivated in many memory retrieval studies, showed set-specific activation in that it was more active during retrieval than encoding. These data demonst rate that distinct regions in the frontal cortex contribute in systematic y et different ways to human memory processing.