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40 Hz steady-state visually evoked potentials recovered during oscillating transcranial electrical stimulation
Laura Hainke1,2,3, Manuel Spitschan2,4,5, Josef Priller1,6,7,8
1Department of Psychiatry and Psychotherapy, TUM School of Medicine and Health, Technical University of Munich, Ismaninger Str. 22, 81675 Munich, Germany.
Biomedical Physics & Engineering Express
|August 21, 2025
Summary
Researchers developed a new EEG method to measure brain activity during combined electrical and visual stimulation. This technique successfully removes artifacts, enabling reliable recording of 40 Hz Steady-State Visually Evoked Potentials (SSVEPs).
Area of Science:
- Neuroscience
- Electrophysiology
- Brain-Computer Interfaces
Background:
- Combining 40 Hz electrical and visual stimulation shows potential but faces challenges in concurrent electrophysiological measurement due to stimulation artifacts and low-amplitude gamma signals.
- Existing methods struggle to isolate genuine neuronal activity from electrical and physiological confounds during combined stimulation paradigms.
Purpose of the Study:
- To develop and validate a robust electroencephalography (EEG) method for recording 40 Hz Steady-State Visually Evoked Potentials (SSVEPs) during concurrent 40 Hz electrical brain stimulation.
- To assess the effectiveness of an adaptive template subtraction approach in removing stimulation artifacts and isolating neural signals.
- To investigate potential interactions between frequency-matched electrical and visual stimulation.
Main Methods:
- Utilized an adaptive template subtraction approach in the time domain for flexible, millisecond-precision artifact removal from EEG data.
- Developed an improved algorithm with refined artifact template fitting, interpolation, and segment rejection criteria for enhanced signal processing.
- Conducted experiments with 25 healthy volunteers, applying 40 Hz electrical stimulation to central and occipital regions alongside visual stimulation.
Main Results:
- Successfully recovered 40 Hz SSVEPs during frequency-matched electrical stimulation, with recorded waveforms closely matching baseline SSVEPs.
- A control condition without visual stimulation confirmed robust artifact removal, yielding uncorrelated low-amplitude signals.
- No significant interactions were found between the electrical and visual stimulation parameters.
Conclusions:
- Demonstrated a reliable EEG method for measuring 40 Hz SSVEPs during concurrent electrical brain stimulation, effectively distinguishing neural activity from artifacts.
- The developed technique provides a valuable tool for researchers combining rhythmic sensory and electrical stimulation in the gamma band.
- Enables precise quantification of neuronal electrophysiological effects in both fundamental and clinical research settings.
