Event-related potential correlates of the interaction between attention and spatiotemporal context regularity in vision.

Visual perception is influenced at early processing stages by geometric spatiotemporal context regularities (consistent with the "vision-as-inference" view) and by attention, yet little is known about the interaction between these two influences on visual processing. Here, we investigate the temporal dynamics of the interaction between attention and spatiotemporal context regularity in target detection using event-related potentials (ERP). Spatial attention was withdrawn from the context by a secondary task in Experiment 1, and the role of task-relevance was explored in Experiment 2 by including a passive viewing condition. The ERP correlates of spatiotemporal regularity reported in an earlier study were replicated in single task (Experiment 1) and active viewing (Experiment 2): P1 and N1 peak-latency was shorter when the target was preceded by a context. Latency first differentiated between the two context conditions at N1, where latency was shortest for targets preceded by a context with both spatial and temporal regularities (compared with temporal regularity only). In dual task and passive viewing, this N1 latency-shift was abolished. Comparisons of "low-attention" (dual task or passive viewing) with "high-attention" conditions (single task or active viewing) revealed that attention only shortened N1 peak-latency when the target was preceded by stimulus sequences with spatial and temporal regularity. P1 latency was unaffected by manipulation of top-down attention factors. Attentional factors are likely to modulate influences of spatiotemporal context through re-afferent projections at later stages of visual processing in regions of extrastriate cortex associated with the generators of the N1 waveform.