Electrophysiological dissociation of the neural correlates of recollection and familiarity

Event-related potentials (ERPs) were employed to investigate electrophysiological correlates of recognition memory in a task that allowed segregation of test items according to whether they were recollected (operationalized by introspective report) or, if recollection failed, their level of familiarity (operationalized by recognition confidence). The amplitude of a negative-going ERP deflection that onsets around 300 ms post-stimulus varied inversely with familiarity strength. This effect was maximal over the left frontal scalp. It did not differ between the ERPs elicited by highly familiar versus recollected items, indicating that the recollection is not merely a consequence of strong familiarity. By contrast, a later positive deflection (onset ca. 500 ms post-stimulus) was enhanced in ERPs elicited by recollected relative to highly familiar items. This effect was maximal over the left posterior scalp and was insensitive to familiarity, as indicated by its absence in the contrast between items judged highly familiar versus highly unfamiliar. The findings constitute a double dissociation between the neural correlates of recollection and familiarity. Together with the results of a parallel functional magnetic resonance imaging study (A.P. Yonelinas et al., J. Neurosci. (2005), 25, 3002–3008), they indicate that recollection and familiarity rely on qualitatively distinct neural systems and strongly support dual-process models of recognition memory.