Additive noise can enhance temporal coding in a computational model of analogue cochlear implant stimulation

Conventional analogue multichannel cochlear implants are unlikely to convey formant information by the fine time structure of evoked discharges. Theor etically, however, the addition of noise to the channel outputs could enhan ce the representation of formants by time coding. In this study, the potent ial benefit of noise in analogue coding schemes was investigated using a co mputer model of cochlear implant stimulation. The cochlear nerve was modell ed by the Frankenhauser-Huxley equations. For all five vowels investigated, the optimal addition of noise to the first channel of the simulated implan t (200-671 Hz) caused enhancement of the first formant representation las s een in amplitude spectra of the simulated discharges). For vowels with a lo w-frequency second formant, clear enhancement of the second formant resulte d from the optimal addition of noise to the third channel (1200-2116 Hz). O n the basis of the present computational study, additive noise would be exp ected to enhance the coding of temporal information by the discharges of a single nerve fiber. (C) 1999 Elsevier Science B.V. All rights reserved.