Relationship between behavioral measure of ANL and its physiological mechanism in the normal hearing participants

Abstract

Context: In previous studies, the efferent mechanism was speculated on low and high acceptable noise level (ANL) groups. Thus, an attempt is made to measure the auditory afferent and efferent mechanisms indirectly through event related potentials on same individuals of different ANL groups. Aims: To study the relationship between behavioral measure ANL and its physiological mechanism. Settings and Design: One shot partly replicative and correlative research design was utilized. Subjects and Methods A total of 40 normal-hearing individuals were classified into low, high and average groups based on ANL. From each study participant the contra-lateral suppression of otoacoustic emission (CSOAE), auditory brainstem response in different fixed levels (50, 55, 60 and 65 dB HL) and also in 5 dB noise above each fixed level of intensity were measured. Kruskal-Wallis test and Pearson correlation statistical analysis were used. Results: The mean amplitude of CSOAE was larger in the lower ANL group than compared to other groups, but this difference was not significant. Further, it was found that the slope of V-A (quiet) in the low ANL group was significantly steeper than the high ANL group (P < 0.05). Similar result was found in slope of V-A (noise) . In addition, the Pearson correlation coefficient result revealed that there was no correlation between global ANL and CSOAE. However, a moderate negative correlation was found between global ANL and the slope of V-A (quiet) and; in slope of V-A (noise) . Conclusion: The slope of V-A in quiet and in noise conditions was found steeper in low ANL group indicating stronger auditory afferent and efferent auditory pathway at the central level