Abstract
Previous research has shown that there are two types of spatial attention, sometimes referred to as voluntary (goal-directed) and involuntary (stimulus-driven) attention. These studies used the spatial-cueing paradigm in which a spatial cue could be predictive of the location of an upcoming target, or not. The target could be in either the cued or uncued location. Within this paradigm, predictive spatial cues engage voluntary attention, while nonpredictive cues capture involuntary attention. Event-related potential (ERP) studies have found no clear difference between the P1 and N1 components for predictive and nonpredictive cues, while studies using time-frequency analysis have found differences in the gamma-band response (30 to 80 Hz). We addressed this disconnect with a direct comparison of these analytical approaches within a single study. Furthermore, in all previous studies target-related activity was confounded with the lingering cue-related response. This is particularly a problem for target-cued trials, which differ in their physical composition from target-uncued trials and, as such, may influence the EEG response to the target. We addressed this overlapping activity in two ways. First, we used a cueing paradigm in which we differentially, but simultaneously, cued both spatial locations. The participants were told that these cues were either random with respect to the target (involuntary attention condition) or that one of the cues would predict the location of the target (voluntary attention condition). This design ensured that every trial was physically identical. Second, we employed a sufficiently long period between the cue and target (600 ms) to allow the ERP signal to return to baseline prior to the appearance of the target. With this design, we were able to separate cue-related and target-related activity both in ERP and time-frequency analyses, and to delineate what aspects of the EEG signal are due to voluntary attention.