Correlation analysis between momentary phases of ongoing EEG oscillations and erp amplitudes to identify the optimal brain state for stimulus presentation

Users of BCI systems are always encouraged to develop and maintain the most discriminable brain signal features that the BCI employs to decipher their intent. Instead of training users to develop new skills or strategies allwoing the users best control their brain signals by rewarding better performance with appropiate feedback, this paper exploited to augment driven neuroelectic responses to externally stimuli by presenting the visual stimulus at the time when brain fall in the state of effective processing the stimulus. Our work present electrophysiological evidence showing that the amplitudes of ERP(event related potential) component P300 indicating the brain recognitive state is actually modulated periodically. Firstly, we separated stimulus evoked response from ongoing spontaneous EEG with differentially variable component analysis (dVCA) method, and then analyzed correlation between amplitudes of P300 and the phase of ongoing EEG oscillations with circular-linear correlation. The ERP component P300 evoked by stimulus may reflect the human cognitive processing, such as visual information recognition, and the ongoing EEG oscillations relate to subsecond fluctuations of neuronal excitability. So, correlation analysis of ERP amplitudes and Ongoing EEG oscillations phases reveal the brain states that conducive for stimulus presentation. Our analysis demonstrated that amplitude of P300 induced with visual stimulus actually fluctuated over time along with the phase of spontaneous oscillations in the alpha (6.6 Hz) frequency band just about 396 milliseconds before stimulus onset. This fluctuation suggests that our perceptional and cognitive system in fact exerts its facilitative effect on P300 in a periodic fashion. Thus, we can record augmented P300 by presenting stilulus during the optimal state conducive for visual stimulus processing. Our study may help to improve reactive BCI where brain activity arise in reaction to external stimulation.