Temporal Processing in Listeners with Unilateral Deafness

Abstract

In general, auditory cortex located in the left hemisphere is specialized for processing of acoustic stimuli with complex temporal and spectral structure, while the right hemisphere is primarily responsible for processing of tonal and music stimuli. This asymmetry is reflected in tasks involving processing such stimuli which are spectrally or temporally different. Also, it is not clear whether cortical reorganization may exist following loss of function in one ear particularly in the case of unilateral profound hearing loss. The present study was aimed to investigate the temporal processing abilities in two groups of right handed listeners: a group of normal hearing listeners and group of listeners with unilateral deafness. Gap detection and temporal modulation transfer function were used as measure of temporal resolution. Gap detection thresholds were determined using broadband noise, 400 and 2000 Hz pure tones individually for the right and left ears. Temporal modulation transfer function was examined using amplitude modulated broadband noise for both right and left ears. These experiments were conducted in the ear with normal hearing for the group with unilateral deafness. It was found that the gap detection abilities of listeners with unilateral deafness show the presence of ear effect in context of temporally complex and simple stimuli. Therefore, a significant effect of asymmetric stimulation has not been revealed in the present study due to absence of any kind of compensation with respect to gap resolution. Invariably, the temporal modulation transfer functions obtained from the two groups of subjects also have a fair amount of similarity. No ear differences were found to be present with respect to processing of modulation detection.