Single-trial EEG analysis reveals burst structure during photic driving.

OBJECTIVE: Photic driving in the human visual cortex evoked by intermittent photic stimulation is usually characterized in averaged data by an ongoing oscillation showing frequency entrainment and resonance phenomena during the course of stimulation. We challenge this view of an ongoing oscillation by analyzing unaveraged data. METHODS: 64-channel EEGs were recorded during visual stimulation with light flashes at eight stimulation frequencies between 7.8 and 23 Hz for fourteen healthy volunteers. Time-frequency analyses were performed in averaged and unaveraged data. RESULTS: While we find ongoing oscillations in the averaged data during intermittent photic stimulation, we find transient events (bursts) of activity in the unaveraged data. Both resonance and entrainment occur for the ongoing oscillations in the averaged data and the bursts in the unaveraged data. CONCLUSIONS: We argue that the continuous oscillations in the averaged signal may be composed of brief, transient bursts in single trials. Our results can also explain previously observed amplitude fluctuations in averaged photic driving data. SIGNIFICANCE: Single-trial analyses might consequently improve our understanding of resonance and entrainment phenomena in the brain.

Entrainment and resonance effects with a new mobile audio-visual stimulation device.

Entrainment and photic driving effects triggered by repetitive visual stimulation are long-established in clinical and therapeutic scenarios. Nonetheless, such stimulation patterns are typically bound to stationary clinical and laboratory applications. We investigated the effects of repetitive stimulation with a new dynamic auditory-visual stimulation pattern using a novel consumer-grade stimulation device for home application.Fourteen volunteers (study group) received 16 sessions of combined auditory-visual stimulation during four weeks. An additional control group (seven volunteers) received auditory-only stimulation for two sessions. From 64-channel electroencephalography recordings, we compared individual alpha peak frequencies (iAPF) between week one and week four as well as power values from the time-frequency analysis.The novel stimulation device yielded stable entrainment and resonance effects for all investigated stimulation frequencies. Both groups showed no differences in their iAPFs between weeks one and four. The power comparison suggests that there are similar entrainment and resonance effects in week one and week four within the study group.We conclude that the novel portable consumer-grade stimulation device is suitable for home-based auditory-visual stimulation leading to consistent entrainment and resonance effects over the course of 16 stimulation sessions over four weeks.

An ecological study protocol for the multimodal investigation of the neurophysiological underpinnings of dyadic joint action.

A novel multimodal experimental setup and dyadic study protocol were designed to investigate the neurophysiological underpinnings of joint action through the synchronous acquisition of EEG, ECG, EMG, respiration and kinematic data from two individuals engaged in ecologic and naturalistic cooperative and competitive joint actions involving face-to-face real-time and real-space coordinated full body movements. Such studies are still missing because of difficulties encountered in recording reliable neurophysiological signals during gross body movements, in synchronizing multiple devices, and in defining suitable study protocols. The multimodal experimental setup includes the synchronous recording of EEG, ECG, EMG, respiration and kinematic signals of both individuals via two EEG amplifiers and a motion capture system that are synchronized via a single-board microcomputer and custom Python scripts. EEG is recorded using new dry sports electrode caps. The novel study protocol is designed to best exploit the multimodal data acquisitions. Table tennis is the dyadic motor task: it allows naturalistic and face-to-face interpersonal interactions, free in-time and in-space full body movement coordination, cooperative and competitive joint actions, and two task difficulty levels to mimic changing external conditions. Recording conditions-including minimum table tennis rally duration, sampling rate of kinematic data, total duration of neurophysiological recordings-were defined according to the requirements of a multilevel analytical approach including a neural level (hyperbrain functional connectivity, Graph Theoretical measures and Microstate analysis), a cognitive-behavioral level (integrated analysis of neural and kinematic data), and a social level (extending Network Physiology to neurophysiological data recorded from two interacting individuals). Four practical tests for table tennis skills were defined to select the study population, permitting to skill-match the dyad members and to form two groups of higher and lower skilled dyads to explore the influence of skill level on joint action performance. Psychometric instruments are included to assess personality traits and support interpretation of results. Studying joint action with our proposed protocol can advance the understanding of the neurophysiological mechanisms sustaining daily life joint actions and could help defining systems to predict cooperative or competitive behaviors before being overtly expressed, particularly useful in real-life contexts where social behavior is a main feature.