High Frequency Oscillation Acquisition System Of Somatosensory Evoked Potential

EEG signal is the synchronous discharge activity of thousands of neuron cells in the same spatial orientation.The traditional EEG signal collection frequency band is mainly concentrated at 0.5～30Hz.There are few studies on the collection of high frequency EEG signals higher than 100Hz,and the physiological significance of different high frequency EEG signals also needs further study.Combined with somatosensory evoked experiment,this paper designs a set of high sampling rate EEG signal acquisition system which can collect low frequency and high frequency EEG signals of sensory-evoked potential.This system is divided into two parts:EEG amplifier and pulsed electrical stimulation.The EEG amplifier includes analog cir-cuit,digital circuit and computer acquisition software.The analog circuit includes sig-nal amplification and filtering,digitization and electrical isolation circuit,which has the characteristics of high input impedance,low noise,high sampling rate and safe electrical isolation.The digital circuit uses FPGA chip to control data transformation and real-time data transmission via USB.The acquisition software on the computer side is written by Qt to realize real-time data receiving,saving and drawing display.The EEG amplifier has 8 signal channels,the sampling rate is 20 KHz,the theoretical design bandwidth is 1.592～1592Hz,the resolution of the anal og-to-digital converter is 24 bits,the peak to peak of the signal reference ground short connection noise is less than 3.5μV,and the common mode rejection ratio of the system can reach more than 109dB(50Hz).Somatosensory evoked pulse electrical stimulation equipment,mainly includes analog Howland current source part and digital control part,stimulation mode is pulse electrical stimulation,high level duration of 200μs,stimulation frequency adjustable 1～30Hz,stimulation intensity adjustable 0.5～20mA.In order to verify the feasibility and stability of the whole system,this paper tested the gain bandwidth,noise and common mode rejection ratio of the EEG amplifier hard-ware.Based on the somatosensory evoked potential test,under the same conditions,respec-tively,using self-made equipment and commercial collected 10 subjects of somatosensory evoked N20,HFOs signal,respectively from the time domain and frequency domain anal-ysis to verify the authenticity of the signal,the related parameters of N20,HFOs has carried on the statistical analysis,finally verify the feasibility of system described in this article,It can be applied to subsequent experimental research.