Research On Auditory Brainstem Response Detection Method Based On Reference Electrode Standardization Technique

Auditory brainstem response(ABR)is an evoked potential collected by electrodes placed on the scalp under specific sound stimuli,and can reflect the functional status of the auditory nerve and brainstem.The ABR has a total of 5 to 7 peaks,each corresponding to a different anatomical location of the auditory system.When the human auditory system has a lesion,it is expressed by the waveform of the ABR,so it is of great significance in clinical applications.In the research and application of EEG,the components of evoked potential(EP)and spontaneous electroencephalogram(EEG)are described by the changes of waveform,latency,polarity and cortical distribution,and the magnitude of these eigenvalues needs a zero potential point as a reference to determine.However,neither the head electrode nor the non-head electrode has an absolute zero potential point.The potential activity at the reference point affects the time domain analysis and spectrum analysis of the EEG signal.Therefore,the choice of reference electrodes has been the key to EEG/EP research.This paper compares the effects of two average reference(AR)and digitally linked mastoid reference(MM)commonly used in EEG/EP studies and a new reference method for mathematical reference design named reference electrode standardization technique(REST)on the waveform morphology,latency and amplitude etc.of ABR.The waveform shape,latency and amplitude of the ABR are affected by various factors.For normal subjects,changing the stimulation intensity and stimulation rate will cause changes in the ABR waveform.This paper mainly compares the effects of AR,REST and MM on ABR waveforms under different stimulation conditions,and compares the morphology,amplitude and distribution features,etc of ABR in different brain regions by waveform analysis and EEG topographic map.Because ABR belongs to short latency potential,which occurs within 10 ms after stimulation.It requires high synchronization of stimulus and trigger signal.In this paper,a stimulus generation module designed by our research group is used.The module is controlled by a platform based on MATLAB,which can achieve more controllable stimulus conditions and stimulus presentation times.The results show that the amplitude of I,III,and V waves obtained by the digitally connected mastoid is the largest,followed by the REST reference,and the smallest amplitude is the average reference.The ABR waveforms obtained by MM reference method and the REST reference method are better,but the amplitudes of I,III and V waves obtained by the MM reference method are larger than those obtained by REST reference method.As the stimulation rate increases,the latency of the V wave is prolonged,and the lower the stimulation rate,the better the waveform differentiation.As the intensity of the stimulus decreases,the latency shifts back and the waveform shape deteriorates.In the single-channel acquisition of ABR,researchers or clinicians usually choose FPz channel or Cz channel,so we prefer the electrode on the midline when discussing a single channel.Therefore,when discussing single channel,we give priority to the middle line electrode.The experimental results show that the ABR waveform of the midline electrode does show good waveform shape,especially Cz channel near the cranial ridge,and its waveform differentiation and repeatability are strong.The waveform obtained by REST reference method is similar to that obtained by digitally connected mastoids and is well differentiated.At the same time,REST reference method has a good effect in hearing threshold exploration.In practical application,the digital mastoid connection method assumes that the potential at the mastoid is zero,but in fact,it is difficult to maintain this hypothesis.The REST reference method transforms the reference potential of a point on the scalp into the reference potential of an infinite point by reconstructing the head model,which is not affected by the head electrical activity.Therefore,it is easy to obtain more real EEG signals by using REST reference method in the study of evoked EEG.