Association between EEG spectral power dynamics and event related potential amplitude on a P300 speller

Objective: Event related potentials (ERPs) are phenomena that produce alterations on the spectral power of different bands synced with stimuli presentation. Such a perspective overlooks that the spectral power time series present spontaneous oscillations, the dynamics of which have been associated with the state of health and could be also linked to superior processes such as attention, memory, or cognition. In this work, amplitude of the ERP has been associated with dynamics of the power spectral density (PSD) time series. Approach: Data from a public P3 speller database were analyzed. Statistics about latency, amplitude and scalp distribution of the ERP confirm correct task realization. The spectral power over alpha, beta and gamma bands were correlated with ERP amplitude, considering such estimations time-locked with stimuli presentation. Additionally, PSD time series over the same bands were constructed using a sliding window not synced with stimulation. From these time series, a scaling exponent was computed using a detrended fluctuation analysis approach, and such indices were correlated with ERP amplitude of all registered electrodes. Main results: The correlation between ERP amplitude and scaling exponents of PSD series achieve statistical significance in almost all channels and for all analyzed bands (excepting alpha at C4). In particular, beta and gamma PSD series achieve R-2 values above 0.6 for Cz. Meanwhile, the correlation analysis with time-locked PSD achieves a statistically significant relationship with ERP amplitude (p < 0.05) but with a coefficient of determination (R-2) below 0.2, only for gamma and alpha over the C4 and Pz channels. Significance: The ERP amplitude and scaling exponent of the PSD time series show an anticorrelated behavior, suggesting that larger ERP amplitudes are elicited when the PSD series are less autocorrelated, similar to white noise, further suggesting that the processes involved in the generation of such dynamics could be related to the mechanisms of cognitive responses.