Early, middle and late components of the auditory evoked response to homophasic and antiphasic stimuli in noise

Abstract

The purpose of this study was to determine whether the masking-level-difference (MLD) obtained with the auditory evoked potential has characteristics similar to those reported for the behavioural masking level difference with respect to the effects of noise level. The study has significant applications for the diagnosis of central auditory processing problems in children. The auditory evoked potential is derived from the small bioelectric potentials recorded from the scalp, similar to that of the Electroencephalogram (EEG). The auditory evoked potential is studied in terms of the early waveform (0-10 msec) originating in the brainstem, the middle latency potential (10-100 msec), and the late or cortical evoked potential (100-350 msec). Six subjects were presented with tonal stimuli that are designed to make use of binaural interaction between the two ears. A hardware was developed to deliver a mixture of homophasic signal and homophasic noise to one ear and a mixture of either homophasic signal or antiphasic signal and noise to the other ear depending on the condition provided. Using standard EEG techniques (non-invasive), surface electrodes were placed on the top of the head and behind each ear (mastoid). The trials were individually saved and evoked potentials were obtained. This study presents a unique methodology to elaborate on binaural interaction and the acquisition of the evoked potential.

Date of Award	Nov 2005
Original language	English
Supervisor	Mirjam Jonkman (Supervisor)