Joint recording of EEG and audio signals in hyperscanning and pseudo-hyperscanning experiments

Measuring auditory time-locked neurophysiological responses requires precise temporal synchrony between the delivery of the auditory signal to the participant and the sending of the digital trigger to the acquisition device. Often due to imprecision in hardware and software, an asynchrony is observed between the stimulus and digital trigger (Bridges, Pitiot, MacAskill, & Peirce, 2020). Recording auditory stimuli jointly with ongoing high temporal resolution neurophysiological recordings presents an efficient and effective way for off-line controlling any time shift between the digital trigger sent by the stimulation program and the actual onset of the auditory stimulus de-livered by the speakers/headphones. This inclusion is straightforward in magnetoencephalographic (MEG) re-cordings, since the system by default includes dedicated channels to record the experimental stimulation; howev-er, it is less common in electroencephalographic (EEG) recordings, where including the auditory signal requires the implementation of additional hardware connections. This configuration is particularly challenging in hyperscanning setups due to the already increased complexity of the methodology. In the case of the pseudo-hyperscanning designs using auditory stimuli, combined EEG-auditory recordings are a key feature, since it is by using the shared audio signal that off-line synchronisation is performed. In the current paper, we describe two hardware configurations wherein the real-time delivered auditory stimulus is recorded jointly with ongoing neuro-physiological recordings. Specifically, we describe and provide customized implementations for joint EEG-audio recording in hyperscanning and pseudo-hyperscanning setups using hardware and software from Brain Products GmbH.