Design Of Portable Wireless Auditory Evoked Potential Experiment System

Auditory evoked potential(AEP)is a kind of bioelectrical activity synchronously occurred at various origins in the auditory neural pathway due to specific sound stimulation.AEPs are widely applied in the field of basic science and clinic.Based on characteristic of different AEPs,auditory brainstem response(ABR)is mainly used in hearing screening and audiometry;and auditory steady state response(AS SR)is another well-established method to record electrophysiological signals for rapid periodical sound stimulation in hearing test,which is used increasingly as a biomarker for brain functions in various neuropsychiatric disorders,such as autism spectrum disorders,schizophrenia and bipolar disorders.Other AEPs,such as P300 or mismatch negativity,are mainly used in cognitive psychology.With the continuous expansion of AEP applications and the rapid development of electronic and computer technologies,the traditional AEP equipment is required to update the functionality and manufacturing with new features such as portability,mobility and wireless transmission performance.In addition,the cost of also have to be addressed for the commercial AEP equipment which is mainly of imported brands such as Otometrics,Vivosonic,Neuroscan,etc.In this article,a portable AEP experiment system with wireless transmission is proposed,which consists of two parts:acquisition and calibration.The acquisition system assemble an EEG collector and an auditory stimulator into a volume of 80*90*30mm3.The communication between EEG collector and auditory stimulator is implemented via an I/O port,which passes control and feedback instructions used to coordinate the playback of the stimulus sound and the synchronous acquisition of the multi-channel EEG signals.The EEG collector is connected to the PC-based interface through Bluetooth module for transmission of the EEG signals up to 8-channels real time data.The whole recording process is automatically controlled by PC program without any involvement from the user.The hardware system can be powered by dry batteries for portable scenario.The calibration system includes the EEG calibrator and the stimulus sound calibrator.The EEG calibrator is a tiny signal generator that generates 1?64Hz sine wave and pulse wave of different widths.The frequency of sine waves can be selected by a DIP switch of 1Hz incremental.The amplitude can be set to 50?V,200?V,2000?V The stimulus sound calibrator is comprised of a 2cc coupler,microphone,preamplifiers,measuring amplifier and an NI data acquisition card.The stimulus data are collected via the acquisition card to the PC for the displayed and further analysis.In this article,four tests were performed to verify performance.First,the stimulus sound was tested using oscilloscope and auditory stimulator to test the features of stimulus sound,and its synchronization with the trigger signal.Second,the transmission performance and distance of Bluetooth module were tested.And then,the electric characteristics of EEG amplifier were tested by the EEG calibrator,including the input impedance and the noise level.Finally,a simple click stimuli sequence was used to conduct the AEP acquisition experiments on 3 human subjects.In summary,this new developed prototype can accomplished the fundamental AEP functionality and can be operated and worked in a durable and stale way with the advantage of portability and low power-consumption.