In visual search, efficient selection of task-relevant objects depends on foreknowledge of their defining characteristics. Internal representations of these features comprise “attentional templates”, which bias attentional processing towards template-matching sensory signals, thereby promoting adaptive top-down selectivity. To proactively facilitate the detection and identification of target objects, target templates are assumed to become activated in advance of an up-coming search episode. However, an immediate neural signal for such preparatory template activation processes has yet to be discovered, so their existence remains elusive.
Here, we introduce the high-definition rapid serial probe presentation paradigm (RSPP-HD) – a method we recently developed to track target template activations in real time via monitoring of the N2pc component. In the RSPP-HD procedure, a series of task-irrelevant probe displays are presented at regular intervals during the period between successive task-relevant search displays. When a corresponding target template is active, lateralised probe stimuli including the target defining feature are expected to attract attention and elicit an N2pc, thereby tracking the temporal profile of preparatory template activation processes. To limit-test the temporal resolution with which such template-guided attentional shifts can be traced, between-probe SOA’s of 50, 100, and 200 ms were evaluated. Our findings demonstrate that the preparatory activation of target templates can be reliably monitored at higher sampling frequencies than previously achieved, without running the risk of confounding template-guided and salience-driven attentional shifts. The RSPP-HD paradigm therefore provides a viable means to approach various unanswered questions regarding the content and temporal dynamics of attentional templates for visual search.