Perceptual organization of sequential stimuli in listeners with cochlear hearing loss.

The perceptual organization of sequential stimuli presumably depends in part on the fidelity with which acoustic cues are encoded in the auditory system. The purpose of this study was to examine the effects of cochlear hearing loss on two measures of sequential processing that rely on spectro-temporal information. The results of a gap detection/discrimination task indicated that listeners with cochlear hearing loss exhibited particular difficulty discriminating gaps between tonal markers that were disparate in frequency. Performance improved when the disparate tones were embedded into a sequence of alternating low- and high-frequency tones that may have facilitated the perceptual of the stimuli into separate auditory streams. However, performance for listeners with cochlear hearing loss was generally poorer than that of normal-hearing listeners and did not appear to be related to threshold in quiet or to frequency selectivity. The results of a melody recognition task that required a target melody to be "heard out" from simultaneous competing melodies also indicated generally poorer performance on the part of the listeners with hearing loss, although the pattern of results across all listeners was highly idiosyncratic. It was concluded that cochlear hearing loss deleteriously affects the processes underlying perceptual organization of sequential stimuli. In particular, perceptual organization in the presence of cochlear hearing loss appears to require a greater frequency separation between presumed auditory streams in comparison to normal-hearing listeners.