P 17 Neural signatures of post-perceptual attention and selective working memory encoding

Abstract

Post-perceptual cues can enhance visual short term memory encoding even after the offset of the visual stimulus. However, both the mechanisms by which the sensory stimulus characteristics are buffered as well as the mechanisms by which post-perceptual selective attention enhances short term memory encoding remain unclear. We analyzed late post-perceptual event-related potentials (ERP) in visual change detection tasks (100 ms stimulus duration) by high-resolution ERP analysis to elucidate these mechanisms. The effects of auditory post-cues (300 ms or 850 ms after visual stimulus onset) as well as the effects of a visual interference stimulus were examined in 27 healthy right-handed adults. Focusing attention with post-perceptual cues at both latencies significantly improved memory performance, i.e. sensory stimulus characteristics were available for up to 850 ms after stimulus presentation. Passive watching of the visual stimuli evoked a slow negative wave over occipito-temporal visual areas. In the memory task, this N700 was strongly reduced by a visual interference stimulus which impeded memory maintenance. Therefore N700 could reflect visual post-processing by automatic attention attraction – when visual post-processing is not impeded by interference effects. In contrast, contralateral delay activity (CDA) still developed after the application of auditory post-cues in the retroactive interference condition. Thus CDA may reflect the top-down process of searching selectively for the required information through post-perceptual attention. N700 and CDA could be dissociated by retroactive interference effects and seem to represent two different processes involved in short term memory encoding. We discuss the meaning of cortical slow negative waves during post-perceptual attention changes in different modalities (olfactory, auditory, somatosensory, motor/proprioceptive, visual) in order to elucidate general mechanisms of the selective encoding of sensory features in working Hecht et al., 2016 , Lenk et al., 2014 , Bender et al., 2014 , Bender et al., 2012 , Bender et al., 2012 , Thiemann et al., 2012 , Bender et al., 2010 .