Selective activation of the ventrolateral prefrontal cortex in the human brain during active retrieval processing

The present study examined the role of the prefrontal cortex in retrieval p rocessing using functional magnetic resonance imaging in human subjects. Te n healthy subjects were scanned while they performed a task that required r etrieval of specific aspects of visual information. In order to examine bra in activity specifically associated with retrieval, we designed a task that had retrieval and control conditions that were perfectly matched in terms of depth of encoding, decision making and postretrieval monitoring and diff ered only in terms of whether retrieval was required. In the retrieval cond ition, based on an instructional cue, the subjects had to retrieve either t he particular stimulus that was previously presented or its location. In th e control condition, the cue did not instruct retrieval but shared with the instructional cues the function of alerting the subjects of the impending test phase. The comparison of activity between the retrieval and control co nditions demonstrated a significant and selective increase in activity rela ted to retrieval processes within the ventrolateral prefrontal cortical reg ion, more specifically within area 47/12. These activity increases were bil ateral but stronger in the right hemisphere. The present study by strictly controlling the level of encoding, postretrieval monitoring, and decision m aking has demonstrated a specific increase in the ventrolateral prefrontal region that could be clearly related to active retrieval processing, i.e. t he active selection of particular stored visual representations.