ANOW RESPONSE RECORDED VIA ELECTROCOCHLEOGRAPHY IN NORMAL HEARING ADULTS

Abstract

Currently, there is no objective hearing measure used clinically that reliably assesses low frequency hearing thresholds (below a 1000 Hz or so). A new measure, the auditory nerve overlapped waveform response (ANOW), holds promise for providing more accurate assessment of low frequency hearing thresholds than currently used objective measures. However, ANOW recordings reported in the literature have been limited primarily to animal studies. This project aims to understand the nature of the ANOW response that is recorded non-invasively from humans. Three within session repeated recordings of the ANOW response using two low frequency TB stimuli (250 Hz and 500 Hz TBs) presented at 7 stimulus intensity levels were obtained from the tympanic membranes of normal hearing adult participants. ANOW’s absolute amplitude, signal-to-noise ratio (SNR), and phase locking value (PLV) measures were used in the analysis. Results revealed significantly stronger phase locking to the stimulus for 250 Hz TB stimulus compared to 500 Hz TB stimulus. Statistically significant effect of the stimulus intensity on all three measures of the ANOW response was revealed for both TB stimuli. Test retest reliability of the ANOW’s amplitude was the highest amongst the three measures, but was dependent on the stimulus intensity level. Unlike SNR measure, PLV measure is not dependent on the amplitude. The deviation from the standard approach of the PLV computation and manipulating the frequency of the TB stimulus may have biased PLV measures and affected test retest repeatability of PLV measures. Hence, developing a technique that would more accurately estimate phase synchronization between ANOW response and stimulus may reveal a new ANOW measure that is reliable across wide range of stimulus intensity levels.