Encoding-specific effects of social cognition on the neural correlates of subsequent memory.
To examine whether social cognition recruits distinct mental operations, we measured brain activity during social ("form an impression of this person") and relatively nonsocial ("remember the order in which person information is presented") orienting tasks. Extending previous research on the neural basis of social cognition, the impression formation task differentially engaged an extensive region of the dorsomedial prefrontal cortex (PFC). In contrast, the nonsocial sequencing task differentially engaged the superior frontal and parietal gyri, precentral gyrus, and the caudate. In addition, we compared encoding activations for subsequently remembered (i.e., hits) to subsequently forgotten (i.e., misses) items. The brain regions in which the blood oxygenation level-dependent signal distinguished subsequent hits from subsequent misses depended on which orienting task was performed at encoding: subsequent memory was correlated with encoding activity only in the medial PFC for impression formation trials but in the right hippocampus for sequencing trials. These data inform two interrelated cognitive issues. First, results underscore the neuroanatomical distinctiveness of social cognition and suggest that previous psychological theories may have neglected important functional differences in how the human brain instantiates social and nonsocial cognitive processes. Second, by demonstrating that activity in different brain regions correlates with subsequent memory as a function of the orienting task performed at encoding, these data provide evidence of the neural basis for encoding specificity, the principle that memory is critically determined by the cognitive process engaged by the initial study episode.