The Design Of Auditory Nerve Stimulator Based On Current Orientation Technology

Hearing is one of the important sensory functions of mankind.The hearing loss will impact on their learning,life and work seriously,and even affect them integrating into society.At present there are drug therapies,surgical therapy and hearing AIDS to treat deafness.Although the above-mentioned therapy for mild deafness patients are useful for hearing recovery,they are ineffective for severe deafness disease.The cochlear implant can directly stimulate the auditory nerve by converting the sound signal into a current pulse,At present,cochlear implants have a good sense of hearing perception in a quiet environment,but the level of auditory perception in the noise environment and music appreciation scenarios needs to be improved.Therefore,it is of great practical significance to improve the resolution of auditory nerve function and to improve the perceived level of cochlear implant.However,due to implantation of auditory nerve stimulation equipment can't have hundreds of channels at the same time to stimulate the auditory nerve,which is not only limited by the current production process,and the unit charge safety density limits the size of the microelectrode can't be infinitely reduced.The directional current technology can improve the number of electrodes without increasing the rate of auditory nerve electrical stimulation,and foreign countries are using large-scale integrated circuit technology to achieve,high technical threshold,high cost.To this end,this article will use the microcontroller,virtual instrument software,discrete electronic components to design a current orientation technology of the auditory nerve electrical stimulator.This paper with the microcontroller MSP430F169 as the control core and combined with digital-analog conversion chip DAC7724 to generate four-channel analog stimulation pulse.And then the voltage signal is converted into a current signal by a voltage-controlled constant current source circuit.Finally,the unipolar pulse is converted into a bipolar pulse by a polarity conversion circuit.And the system hardware circuit corresponding to the software program design includes two parts: the host computer program design and the lower computer program design.The upper computer program uses LabVIEW to design the current orientation coefficient ?,the stimulating current frequency,the stimulating current size and the stimulating current pulse width.The lower one is designed to generate the stimulus waveform and set up the current orientation coefficient and adjust the stimulus parameters of the program in the IAR EW430 development environment by using C language.After the hardware and software design of the system is completed,the total current source linearity,constant current characteristics,output waveform and stimulation parameters of the auditory nerve stimulator are tested.The results showed that the indicators of the stimulator basically reached the expected target.Finally,the experimental results showed that the stimulator could stimulate the response of guinea pig auditory neurons.In conclusion,the auditory nerve stimulator developed in this paper can effectively improve the auditory resolution without increasing the stimulation electrode,which not only can stimulate the adjustment of the parameters,but also can meet the research requirements of the laboratory.