Single-trial EEG and MEG alpha-band photic driving effects

Abstract

In recent years, interest in the single-trial analysis of electroencephalography (EEG) and magnetoencephalography (MEG) data has grown, driven by the need for a better understanding of instantaneous brain states and improved signal-to-noise ratios. So-called transient events, or bursts, have been shown to be the building blocks of well-known, established patterns in processed, i.e. averaged, electrophysiological recordings. To better understand the generation mechanisms and the frequent intra- and interindividual differences that occur during intermittent photic stimulation (IPS), we analyzed the effects of photic driving during individualized IPS in single-trial EEG and MEG in relation to transient events. Fifteen healthy volunteers received IPS at eight different stimulation frequencies, depending on their individual alpha peak frequencies (iAPFs). EEG and MEG were recorded simultaneously during the procedure. Transient events were detected during stimulation at and around the iAPF of each volunteer. The events were characterized by their number, frequency, power and time and frequency width. The main finding was that the number and frequency of events differed significantly across the various stimulation frequencies. The stimulation frequencies fstim = 0.7 × iAPF and fstim = 1.3 × iAPF produced notably different results compared to those around fstim = 0.5 × iAPF and fstim = 1.0 × iAPF. The results presented here extend the conventional (averaging) analysis of photic driving effects and reveal the importance of transient event number and frequency during photic stimulation to describe entrainment and resonance (photic driving) effects. This study improves our understanding of photic driving effects by contributing a characterization of transient events in single trials with varying stimulation frequencies.