Behavioral/Systems/Cognitive Separable Prefrontal Cortex Contributions to Free Recall

In everyday life, we often must remember the past in the absence of helpful cues in the environment. In these cases, the brain directs retrieval by relying on internally maintained cues and strategies. Free recall is a widely used behavioral paradigm for studying retrieval withminimal cue support. During free recall, individuals often recall semantically related items consecutively—an effect termed seman-tic clustering—andprevious studies have sought to understand clustering to gain leverage on the basicmechanisms supporting strategic recall. Successful recall and semantic clustering depend on the prefrontal cortex (PFC). However, as a result of methodological limita-tions, few functional magnetic resonance imaging (fMRI) studies have assessed the neural mechanisms at encoding that support subse-quent recall, andnone have tested the event-related correlates of recall itself. Thus, it remains openwhether one or several frontal control mechanisms operate during encoding and recall. Here, we applied a recently developed method (Öztekin et al., 2010) to assess event-related fMRI signal changes during free recall. During encoding, dorsolateral prefrontal cortex (DLPFC) activation was predictive of subsequent semantic clustering. In contrast, subregions of ventrolateral prefrontal cortex (VLPFC) were predictive of subsequent recall, whether clustered or nonclustered, and were inversely associated with clustering during recall. These results suggest that DLPFC sup-ports relational processes at encoding that are sufficient to produce category clustering effects during recall. Conversely, controlled retrieval mechanisms supported by VLPFC support item-specific search during recall