Beyond flickering: introducing code-modulated motion visual evoked potentials for brain-computer interfacing

This study presents a novel code-modulated motion visual evoked potential (c-MVEP) paradigm for brain-computer interfacing (BCI). To avoid the visual discomfort and fatigue often associated with traditional flickering stimuli, this paradigm uses pseudo-random sequences to visually stimulate objects using motion. We conducted offline and online experiments, to investigate signal characteristics and evaluate practical feasibility, respectively. In the offline experiment, EEG data were recorded and compared during sequential stimulation of a single target under four conditions: c-MVEP, code-modulated visual evoked potential (c-VEP), steady-state motion visual evoked potential (SSMVEP), and steady-state visual evoked potential (SSVEP). The c-MVEP evoked similar temporal and broadband spectral responses as c-VEP, with a comparable signal-to-noise ratio (SNR), although c-MVEP responses were more focused in the lower frequency range. While SSMVEP and SSVEP both showed clear harmonic oscillations, SSVEP yielded higher SNRs. Spatially, both motion-based stimulations peaked at Oz but spread across multiple electrodes, whereas both flicker-based stimulations were more localized at Oz. In the online experiment, we evaluated a four-target BCI using the same four conditions, testing the practical feasibility of the c-MVEP paradigm. The c-MVEP BCI reached a mean accuracy of 85.67% with an average selection time of 2.61 s, which was significantly lower than c-VEP (97.81%; 1.15 s) and SSVEP (93.42%; 1.94 s), but significantly higher than SSMVEP (64.91%; 4.18 s). The subjective ratings revealed no clear preference between the motion- and flicker-based paradigms, indicating comparable user comfort. Overall, this study demonstrates the strong potential of the newly proposed c-MVEP paradigm. By providing an effective, non-flickering alternative to traditional c-VEP and SSVEP, c-MVEP offers a highly viable approach for user-friendly BCI applications.