Early cortical processing of vection-inducing visual stimulation as measured by event-related brain potentials (ERP)

Visual motion stimuli can induce the perception of self-motion in stationary observers (known as vection). In the present study, we investigated the sensory processing underlying vection by measuring the human event-related brain potentials (ERPs) elicited by the movement onset of a visual stimulus. We presented participants a visual stimulus consisting of alternating black-and-white vertical bars that moved in horizontal direction, creating the sensation of vection. The stimulus was presented on a screen that was divided into a central and a surrounding peripheral visual area. Both areas moved independently from each other, resulting in four different movement patterns: the peripheral and the central stimulus moved in the same or opposite direction, or one of the two visual areas of the stimulus moved while the other remained stable. In addition, two different stimulus types varying with respect to the bars' width (narrow vs. wide) were used. Participants were presented with these stimuli in two phases of the experiment: During EEG-recording, only short phases (2.5-3.5 ms) of visual motion were applied. In a separate rating phase, visual motion was presented for 45 s. In this phase, vection onset, intensity, and duration were verbally recorded. Overall, the visual stimulation generated vection with different intensities (Le., weakest vection with sole central stimulus movement). Stimulus type did not affect vection. In the ERPs, stimulus onset elicited parieto-occipital P2 and N2 components. The amplitudes of the ERP components differed significantly between the four movement patterns (irrespective of stimulus type), however, they did not fully align with the subjective vection ratings. Since the ERPs are associated with early sensory processing preceding vection, we argue that the ERPs mirror the contribution of sensory cortical processes to vection rather than the subjective sensation of vection per se.