Pitch perception conveyed by cochlear implant and tactile stimulation

The healthy auditory system encodes acoustic frequency as a tonotopic and synchronous neural response. Cochlear implants (CIs) excite tonotopic organization through place of stimulation and excite a synchronous neural response through stimulation timing, but typically limited to amplitude modulations less than 300 Hz. The results from two experiments will be presented. The first experiment uses CI stimulation to examine the contributions of place and rate of stimulation to pitch perception. Frequency discrimination thresholds were measured in adult CI users for fundamental frequencies ranging from 100 to 1600 Hz. Stimulation was controlled to probe pitch sensitivity as conveyed by place, rate, and covaried place and rate of stimulation. Subjects received a significant low-frequency benefit from combined stimulation, which diminished above 400 Hz as stimulation rate no longer provided a salient sense of pitch. The second experiment considers how well tactile stimulation can be used to augment pitch perception in CIs. Tactile discrimination thresholds were measured for 55 and 110 Hz. Preliminary results will be presented for the second experiment designed to test how well CI users can combine pitch cues provided by stimulation rate and by tactile stimulation.