Searching for the Neurophysiological Correlates of Context Updating

Effective working memory (WM) functioning depends on a gating process which
regulates maintenance and updating. Our aim was to characterize the behavioral
and neural correlates of updating and gating. First, we investigated the relationship between WM updating and the P3b component. The Context Updating Model suggests that the P3b should increase with changes in the internal schema, namely when WM is being updated. We examined this hypothesis in the 1-back task, which requires WM updating, and in a two-alternative forced choice (2AFC) task, which involves updating that presumably occurs outside WM. Stimulus alternation only had an effect in 1-back, but not in the 2AFC, however in the opposite direction than predicted. Specifically, the P3b amplitude was smaller in alternation than in repetition trials, although alternation (rather than repetition) requires updating. Next, we will introduce a new paradigm: the reference-back task. This paradigm enables to empirically distinguish between the set of processes involved in typical n-back tasks: WM updating, comparison, gating and automatic updating. The ERP results from this task replicated the pattern observed in 1-back task, and suggest that the P3b might be related to a categorization process rather than WM updating. Finally, we show that event-based eyeblink rate (ebEBR), which presumably reflects phasic striatal dopamine activity, is correlated with WM updating and gating in the reference-back task. The implications of these finding for understanding the P3 will be discussed.