Abstract:
Many cochlear-implant users show postoperative improvement in the ability to hear speech but most rely on lip-reading to understand speech. To determine if this limitation on speech perception relates to impaired temporal resolution, and, thus, an inability to track rapid frequency changes which are characteristic of speech, temporal resolution thresholds (TRT) of adult implant users were determined by measuring their ability to discriminate between a glide signal, a sinusoid linearly modulated in frequency and a step signal, a sinusoid traversing the same frequency range but in two to five discrete steps. Performance of implanted subjects was extremely variable, but, generally, their TRTs were higher than those of age- and sex-matched normal-hearing controls. At certain frequencies and sweep extents, no implanted subjects were able to distinguish between step and glide signals of duration shorter than 300 ms. When the signal step number was no greater than two, one subject, using a Spectra speech processor, had TRTs near the 10 ms upper limit of the control TRTs. Extended frequency sweeps of 1350--1500 Hz with center frequencies of 3300--3400 Hz resulted in nearly normal TRTs for two of the implant users. [Work supported by the Dayton, OH VAMC and a grant from AFOSR.]