Multi-channel electroencephalogram detection system compatible with transcranial magnetic stimulation

Transcranial magnetic stimulation combined with electroencephalogram (TMS-EEG) has become a powerful way to study the excitability, plasticity and connectivity between different regions of the brain. Conventional EEG acquisition equipment, under the TMS operating environment, causes the amplifier to be saturated for a long time. How to solve the interference caused by TMS on EEG and minimize the loss of information is an important challenge nowadays. Therefore, in order to obtain clean TMS-EEG signals, a TMS-compatible multi-channel EEG detection system is proposed in this paper. Firstly, in order to improve the compatibility and accuracy of the acquisition system, the multi-channel data acquisition card uses a synchronized attenuation circuit and a high-speed 24-bit analog-to-digital converter (ADC). Then, an interpolation algorithm based on Hermite is improved for the artifacts caused by the pulsed magnetic field generated by the TMS device. Finally, in order to judge the device, the ADC on the acquisition card is calibrated first, and then the static and dynamic characteristics of the system are evaluated. The experimental results show that the average absolute error of the corrected ADC is 1.54μV and the integration nonlinearity error is 0.41 ppm; the average channel signal-to-noise ratio is 108 dB, the crosstalk is −98 dB, the spurious-free dynamic range is 112 dB, and the total harmonic distortion is −109 dB. It proves that the system has the advantages of multi-channel, data throughput, synchronization, and visualization.