Magnetoencephalographic correlates of processes supporting long-term memory judgments

The sensitivity of event-related fields (ERFs) to memory retrieval processes is not well determined. This stands in sharp contrast to event-related potential (ERP) studies, as ERPs have been employed widely to address questions about the functional architecture supporting memory retrieval. Despite their success in this endeavour, however, the sensitivity of ERPs to one retrieval process-familiarity-is somewhat limited. This experiment was designed to determine the sensitivity of ERFs to familiarity, and thus to examine the functional leverage that is available to investigate item familiarity via magnetic means of indexing retrieval processing in real-time. The analyses of the ERF data focused on old/new effects, which are differences between the neural activities associated with old (previously studied) and new test items that attract correct memory judgments. The ERFs showed a level of sensitivity to changes in item familiarity superior to that reported previously in very similar studies where ERPs were acquired. Moreover, analyses of the ERF data revealed four functionally distinct old/new effects. These findings provide strong incentives for employing ERFs in subsequent studies of human memory retrieval processing operations.