Binaural Fusion, Masking Level Differences, and Auditory Brainstem Responses in Children with Auditory Processing Disorders.

Abstract

The purpose of this investigation was to explore brainstem level auditory function in an experimental group of 18 children identified as having auditory processing disorders, on the basis of a previously administered auditory-language test battery. Eighteen normal children, matched for age and sex, served as a control group. Three auditory neuromaturational tests which purport to evaluate brainstem-level auditory processing were selected as research instruments. They included: (1) binaural fusion for dichotically and diotically presented passb and s of filtered speech, (2) binaural masking level differences (MLD) for tonal stimuli, and (3) auditory brainstem responses (ABR) for click stimuli. Statistical analysis revealed differences between the two groups on the binaural fusion test, with the experimental group scoring significantly lower on both the dichotic and diotic listening conditions. The MLD and ABR measures did not differentiate the two groups. In view of the experimental group's normal MLD and ABR performance, and their significantly lower scores on the diotic as well as dichotic listening conditions for the binaural fusion task, it was concluded that no definitive evidence of brainstem level auditory processing dysfunction was demonstrated. It was hypothesized that the reduced binaural fusion performance may have been due to a cortical level disorder of perceptual processing rate which was revealed by the low redundancy listening conditions imposed by acoustic filtering. Thus, it appeared that the experimental group's abnormal performance on the previously administered auditory-language measures was not due to auditory processing dysfunction at the level of the brainstem. Furthermore, it was concluded that the binaural fusion test, though potentially useful as an identification test, should not necessarily be considered specific to brainstem level auditory processing in children unless normal cortical level processing can be assumed. Practical and theoretical implications of these findings were discussed.