Electrophysiological evidence for greater attention to threat when cognitive control resources are depleted

In this study, we investigated the time course of attentional bias for threat-related (angry) facial expressions under conditions of high versus low cognitive (working memory) load. Event-related potential (ERP) and reaction time (RT) data were recorded while participants viewed pairs of faces (angry paired with neutral face) displayed for 500 ms and followed by a probe. Participants were required to respond to the probe while performing a concurrent task of holding in working memory a sequence of digits that were either in the same order (low memory load) or in a random mixed order (high memory load). The ERP results revealed that higher working memory load resulted in enhanced lateralized neural responses to threatening relative to neutral faces, consistent with greater initial orienting of attention to threatening faces (early N2pc: 180-252 ms) and enhanced maintenance of processing representations of threat (late N2pc, 252-320 ms; SPCN, 320-500 ms). The ERP indices showed significant positive relationships with each other, and also with the behavioral index of attentional bias to threat (reflected by faster RTs to probes replacing angry than neutral faces at 500 ms), although the latter index was not significantly influenced by memory load. Overall, the findings indicate that depletion of cognitive control resources, using a working memory manipulation, increases the capacity of task-irrelevant threat cues to capture and hold attention.