Gaze intersection points reveal the onset of visual processing during eye and head movement

This study explored the dynamics of steady-state visual evoked potentials (SSVEPs) amid unrestricted head and eye movements using immersive virtual reality (VR) to concurrently record eye and head movement data with a 64-channel electroencephalogram (EEG) during a visual fixation task. Employing a dual-condition approach—eye-shifting and head-turning—the trials were time-locked to stimulus onset, Gaze Intersection Point (GIP) onset, and fixation onset. Eye and head velocity, Canonical Correlation Analysis (CCA) correlation, and Inter-Trial Coherence (ITC) were computed across the trial duration. SSVEP signal detection (reflected in CCA scores) was most closely aligned with the GIP onset. The CCA score increase before fixation suggests that visual processing is not fully suppressed during simultaneous head and eye movements. These findings support the potential of SSVEP for tracking the time course of visual processing in naturalistic settings where research participants are free to move their heads and eyes as they explore their three-dimensional environment.