Visuospatial attention modulates audiovisual temporal perception: Context-dependent associations between prestimulus alpha lateralization and perceptual reports.

Abstract

Audiovisual temporal perception depends on the timing of sensory events and on preparatory attention. We examined how visuospatial cueing affects explicit synchrony judgments and sound-induced flash illusions, and how prestimulus EEG relates to these perceptual reports. In Experiment 1 (N = 39), participants judged beep-flash synchrony across auditory- and visual-leading stimulus onset asynchronies (SOAs). In Experiment 2 (N = 36), they reported flashes in fusion and fission conditions across SOAs and corresponding references. Experiment 1 showed a Cue validity × SOA interaction, with more synchrony reports on valid trials at -100 and +50 ms. Cueing shifted the point of subjective simultaneity among 21 participants with reliable fits. Trial-level posterior alpha lateralization was associated with synchrony reports as a function of Cue validity. In Experiment 2, valid cues reduced raw fusion reports at -100, -50, and +100 ms. A Cue validity × SOA interaction persisted for reference-adjusted fusion scores, whereas neither raw nor adjusted fission showed a corresponding interaction. The association between reference-adjusted alpha lateralization and fusion reports varied with Cue validity and SOA, although a direct comparison with the visual reference did not establish an illusion-specific association. These EEG-behavior associations were stable after accounting for temporal progression, preceding trials, cue side, and an ocular-sensitive EEG proxy. Together, the findings indicate timing- and context-dependent effects of visuospatial attention on audiovisual temporal perception and identify preparatory posterior alpha lateralization as a correlate of subsequent reports.