Gating by inhibition during top-down control of willed attention

In natural settings, the control of attention may be influenced both by external information as well as internal decision-making processes driven by intent (e.g. free will). In past studies of spatial attention, we and others have developed experimental paradigms that permit individuals to choose where to direct their attention on a trial-by-trial basis in the absence of instructive external cues - we term this willed attention. Here we investigate the electrophysiological correlates of willed attention by recording EEG activity when subjects decided to focus covert attention on one of two lateralized target locations versus when they decided to maintain attention at fixation. Independent of the direction of attention, decisions to attend, relative to decisions not to attend, resulted in significant increases in both frontal theta (4-7 Hz) power and central alpha (8-13 Hz) power. We found that focusing spatial attention, as indexed by occipital alpha lateralization was predicted across subjects by the decision-related alpha increases over central scalp regions, but not changes in frontal theta power. This finding is interpreted in terms of the Gating by Inhibition model, where the central alpha EEG signals reflect cortical inhibition of decision processes that lead to the expression of willed attention.