ERP correlates of intentional forgetting.

In this study we investigated the neurocognitive processes underlying the control of memory retrieval. In a Think/No-Think paradigm, adopted for the use in an event-related potential (ERP) experiment, participants learned word pairs and were subsequently presented with cue words and asked to either suppress or to recall the target word. During final cued recall tests for all initially learned targets, memory for the to-be-suppressed or to be-recalled items were tested. Memory for to be-recalled items was enhanced but no forgetting of to-be-suppressed items was obtained. The ERPs in the test phase were separated on the basis of prior learning success and failure, allowing separate analyses of strategic memory control, i.e. attempts to retrieve or to avoid retrieval and the outcome of these processes, i.e. successful retrieval and retrieval avoidance. An early P2 component and a parietal positivity were related to retrieval attempts and a centro-parietal N2 component was associated with attempts to avoid memory retrieval. The parietal positivity was attenuated for No-Think trials on learned items, for which item-specific memories exist. However, under the present testing conditions and in contrast to prior studies (Bergström, Velmans, de Fockert, Richardson-Klavehn, 2007) the parietal positivity was also sensitive to mere retrieval attempts. To examine whether similar neural systems are involved in the inhibitory control of unwanted memories and prepotent motor responses, a motor stopping experiment using a stop signal task was conducted with the same participants. Successful stopping was associated with an enhanced stop signal N2 that showed a similar centro-parietal scalp distribution as the aforementioned N2 to No-Think trials. As both components were significantly correlated, we assumed that some of the systems recruited to override prepotent motor responses are also involved to suppress memory retrieval.