Attention Periodically Binds Visual Features As Single Events Depending on Neural Oscillations Phase-Locked to Action

Recent psychophysical studies have demonstrated that periodic attention in the 4-8 Hz range facilitates performance on visual detection. The present study examined the periodicity of feature binding, another major function of attention, in human observers (3 females and 5 males for behavior, with 7 males added for the EEG experiment). In a psychophysical task, observers reported a synchronous pair of brightness (light/dark) and orientation (clockwise/counterclockwise) patterns from two combined brightness-orientation pairs presented in rapid succession. We found that temporal binding performance exhibits periodic oscillations at ∼8 Hz as a function of stimulus onset delay from a self-initiated button press in conditions where brightness-orientation pairs were spatially separated. However, as one would expect from previous studies on pre-attentive binding, significant oscillations were not apparent in conditions where brightness-orientation pairs were spatially superimposed. EEG results, while fully compatible with behavioral oscillations, also revealed a significant dependence of binding performance across trials on prestimulus neural oscillatory phases within the corresponding band. The peak frequency of this dependence was found to be correlated with intertrial phase coherence (ITPC) around the timing of button press in parietal sensors. Moreover, the peak frequency of the ITPC was found to predict behavioral frequency in individual observers. Together, these results suggest that attention operates periodically (at ∼8 Hz) on the perceptual binding of multimodal visual information and is mediated by neural oscillations phase-locked to voluntary action. Recent studies in neuroscience suggest that the brain's attention network operates rhythmically at 4-8 Hz. The present behavioral task revealed that attentional binding of visual features is performed periodically at ∼8 Hz, and EEG analysis showed a dependence of binding performance on prestimulus neural oscillatory phase. Furthermore, this association between perceptual and neural oscillations is triggered by voluntary action. Periodic processes driven by attention appear to contribute not only to sensory processing but also to the temporal binding of diverse information into a conscious event synchronized with action.