ERP Signatures of Stimulus Choice in Fixed-Gaze BCI Communication
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This study investigated event-related potential (ERP) markers—specifically P3 and Contingent Negative Variation (CNV)—elicited during the mental selection of motivational pictograms representing fundamental human needs, aiming to inform brain–computer interface (BCI) development for individuals with severe motor impairments (locked-in syndrome, LIS) including ocular movements. Methods: Stimuli were drawn from the PAIN Pictionary, an iconographic database designed for non-verbal communication in LIS contexts. Neural activity was recorded using high-density EEG in 30 neurologically healthy right-handed adults who consistently maintained gaze on the central fixation point. They viewed randomized sequences of pictograms representing ten need categories, with one category serving as the target in each sequence. Each pictogram was followed by a visual cue prompting a button press. During training, participants executed actual button presses; in the main task, they engaged in motor imagery, mentally simulating the press while maintaining fixation. Results: ERP analyses revealed a robust P300 over centro-parietal sites following target cues, reflecting attentional allocation and decision-making. Motor-related CNV activity emerged in left premotor regions, indexing anticipatory preparation of the right hand, and a late P600 was observed in response to prompts, consistent with stimulus choice and response monitoring. Conclusions: These findings demonstrate that pattern-onset ERP components can be modulated solely by motor imagery, independent of overt responses or gaze shifts, providing evidence that intentional, need-related communicative states can be decoded from EEG. Source reconstruction revealed that target-related motor imagery recruited a distributed network including prefrontal, premotor, motor, parietal, and limbic regions, integrating attentional, motor, and motivational processes. Collectively, these results establish a neural basis for BCIs enabling thought-driven communication in individuals with profound motor impairments.