Alpha-band fluctuations represent behaviorally relevant excitability changes as a consequence of top–down guided spatial attention in a probabilistic spatial cueing design

Abstract

Abstract Spatial attention is a key function enabling the selection of relevant information and meaningful behavioral responses and is likely implemented by different neural mechanisms. In previous work, attention led to robust but uncorrelated modulations of Steady-State-Visual-Evoked-Potentials (SSVEPs) as a marker of early sensory gain and visual as well as motor alpha-band activity. We probed the behavioral relevance of attention-modulated trial-by-trial fluctuations of these measures. For this purpose, in an experiment with a classical probabilistic visuospatial attention cueing task, a to-be-discriminated target stimulus was validly, neutrally, or invalidly cued, while behavioral responses and EEG were recorded. Single-trial flicker-driven SSVEPs, visual and motor alpha-band activity were measured and the relationship between their amplitudes and reaction times was modeled via Bayesian regression models, respectively. We replicated previous findings that these neural measures and behavioral responses were overall modulated by the attentional cue. Beyond that, SSVEP amplitudes were not associated with behavior, while single-trial alpha-band amplitudes were predictive of reaction times: For trials with a valid or neutral cue, lower visual and motor alpha-band amplitudes measured contralateral to the target in the cue–target interval were associated with faster responses (and for valid cues also higher amplitudes ipsilateral to the target). For invalid cues, which required attentional reallocating to the uncued side, no such relationship was found. We argue that behavioral relevance of alpha-band modulations is a consequence but not a mechanism of top–down guided spatial attention, representing neural excitability in cortical areas activated by the attentional shift.