The addition of noise to speech signals coded by an analogue multichannel c
ochlear implant has previously been shown in modelling studies to enhance t
he representation of speech cues by the fine time structure of evoked nerve
discharges. The enhancement, however, occurred only for a range of noise l
evels, and this range was stimulus dependent. Theoretically, fine optimizat
ion of the noise levels would be unnecessary if each implant channel stimul
ated a group of cochlear nerve fibres such that each fibre in the group rec
eived an independent noise waveform in addition to the same information-bea
ring signal. We present results from computer simulations that suggest that
current spread in the cochlea may be exploited to obtain a high degree of
independence between the noise waveforms that stimulate adjacent fibres. Th
e model simulated monopolar stimulation of a cochlear nerve by 11, 21 or 41
electrodes in the scala tympani. The correlation between the effective sti
muli for pairs of nerve fibres and the correlation between the correspondin
g evoked discharges were calculated for two noise strategies. In one strate
gy, an independent noise current was applied to each electrode. Less correl
ation between effective stimuli was obtained with the alternate strategy th
at used inhibition between the noise sources. (C) 2000 Elsevier Science Ltd
. All rights reserved.