Microprocessor-based auditory brainstem response (ABR) simulator.

Abstract

A low-cost, microprocessor-based instrument is designed to simulate the human auditory brainstem response (ABR) to acoustic clicks. the device normally delivers a continuous simulated EEG signal in the absence of click input. When an acoustic click is sensed, its onset and intensity are recognised promptly and an appropriate ABR waveform is superimposed on the ongoing EEG. Fast recognition of onset and intensity are achieved by using analogue detector circuits which issue microprocessor interrupts. The output waveform is synthesised by a 16-bit D/A convertor to preserve realistic signal (ABR) to noise (EEG) ratios. As multiplication operations cannot be performed at speeds appropriate for ABR waveform simulation, superposition is accomplished by position-weighted loading operations in a 16-bit register. The instrument is tested using a microcomputer-based signal averager. it satisfactorily simulates the randomness of single sweeps. Upon averaging enough sweeps, an ABR waveform is obtained. The device, believed to be the first available of its kind, is used to test and calibrate clinical EP systems and is expected to prove useful as a clinical engineering tool in hospitals and medical centres.