Figure 2. Alpha-band oscillations enable spatially and temporally resolved tracking of covert spatial attention.

(a) Alpha CTFs precisely track where attention is deployed following an attentional cue. Observers performed a spatial-cueing task (left). A central cue (a cross with one uniquely colored arm) directed observers to attend one of eight place holders. After delay, a target digit was presented among distractor letters and then masked with a pound sign. The plot on the right shows the reconstructed alpha CTFs across time for each of eight locations. A channel offset of 0° corresponds to the channel tuned for the cued location. The yellow band in each subplot shows the peak channel response, which tracked the cued location start around 300 ms after cue onset. (b) The time course of alpha-band CTFs track the latency of target selection during visual search. Observers searched for a target (a vertical or horizontal bar) among distractors and reported the orientation of the target (left). The plots on the right show the selectivity of target-related CTFs as for easy and hard search (upper) and as a function of response times regardless of search condition (lower). Spatially selective activity that tracked the target position emerged earlier during easy search than during hard search, and earlier on trials with fast RTs than on trials with slow RTs. Adapted from [11].