Biology subjects

Hainke, L.

Publications and source records attributed to Hainke, L..

2 recordsLinked to original sources

bioRxiv2026

Audiovisual stimulation using wearable shutter glasses robustly evokes 40 Hz neuronal activity but does not modulate associative memory

Audiovisual stimulation is a promising approach for studying and modulating human neuronal gamma (>30 Hz) oscillations and associated memory processes. Portable setups can increase ecological validity and therapeutic potential, but options remain limited. See-through shutter glasses are a new mobile technology that adds a visual flicker effect to what the user naturally sees. Here, we validated this method in a multisensory, cognitively relevant setting. We leveraged a previous experimental design from our lab, aiming to A) characterise the neuronal gamma activity evoked by shutter glasses, and B) conceptually replicate the previously reported effect of audiovisual gamma stimulation on memory accuracy, in line with a Spike Timing Dependent Plasticity model. We recorded high-density Electroencephalography (EEG) from 24 healthy participants during an associative memory task. Video-sound pairs were presented with the sound amplitude-modulated at 40 Hz and 40 Hz visual flicker elicited by the shutter glasses, with a phase offset between both modalities. The visual flicker preceded the auditory modulation by 90 or 270 degrees. Participants were asked to remember the video-sound associations. They also underwent a visual-only condition and an electrically equivalent control condition. EEG evoked power and phase coherence were reconstructed at source level and analysed along with behavioural accuracy. As expected, the shutter glasses robustly increased EEG evoked power and phase coherence at 40 Hz compared to the control condition. Effects were widespread and stronger than in a previous study not using shutter glasses. However, we did not replicate the previously reported effects of audiovisual phase offsets on memory accuracy. This could be due to reduced statistical power or methodological differences. Nonetheless, the validation of shutter glasses in a multisensory setting and the EEG analysis software, now improved and open source, enable important further investigations of audiovisual gamma stimulation in research and clinical settings.

neuroscience↗

bioRxiv2024

Visually Evoked 40 Hz Gamma Activity Enhanced by Transcranial Electrical Stimulation

ObjectiveTranscranial Electrical Stimulation and Visual Stimulation in the gamma band (30-100 Hz, especially 40 Hz) are increasingly used to study and even enhance human cognition. Combining both techniques would be of scientific and clinical value, provided that Steady-State Visually Evoked Potentials (SSVEPs) are measured concurrently to determine any neuronal effects of the electrical brain stimulation. This poses a substantial methodological challenge. We aimed to demonstrate that recording visually evoked 40 Hz activity with EEG during electrical brain stimulation is possible and to explore potential interactions. ApproachWe tested if electrical and visual stimulation might interact depending on which brain areas are electrically stimulated (Experiment 1; N=25) and how closely the respective frequencies match (Experiment 2; N=25). Experiment 3 (N=25) assessed how effectively the data processing pipeline can mitigate electrical artefacts and recover real evoked neuronal activity. SSVEPs were processed and analysed in the time domain using an optimised adaptive template subtraction approach. Main Results40 Hz SSVEPs were successfully recorded during frequency-matched electrical stimulation applied between central and occipital regions. Waveform correlations revealed that SSVEPs from combined visual and electrical stimulation were more similar in shape to baseline SSVEPs from visual stimulation alone than to control data from electrical stimulation alone. Accordingly, during combined stimulation, the recovered signals were stronger in amplitude than the electrical control data. We found no evidence of interactions between electrical and visual stimulation. SignificanceWe demonstrated that 40 Hz SSVEPs can be reliably measured with EEG during frequency-matched electrical brain stimulation, distinguishing neuronal activity from electrical or physiological confounds. This method enables fundamental and clinical researchers to combine rhythmic sensory and electrical stimulation in the gamma band and concurrently quantify neuronal electrophysiological effects.

neuroscience↗