Prelingually deafened patients with bilateral cochlear implants (biCI) often show impaired sensitivity to interaural time differences (ITDs). Recent research of our groups has shown that neonatally deafened (ND) rats, supplied with biCI in young adulthood, can effectively learn to use ITDs for sound localization if the implants are precisely synchronized resulting in the presentation of informative pulse timing (pt) ITDs. Here we investigate whether the inexperienced auditory system can develop good ITD sensitivity when the ptITDs are jittered from onset of electric stimulation.

ND biCI rats were trained to lateralize pulse trains with jittered ptITDs and interaural level differences (ILDs). ITDs were drawn independently from a set of ±{0, 20, 40, 60, 80, 100, 120} μs. ILDs were drawn independently from a set of ±{0, 1, 2, 3, 4, 5} dB. Jitter values changed per pulse and were randomly drawn from a distribution ranging from -60 μs to +60 μs in 20 μs steps. After 5 weeks of training, rats were tested on ITD and ILD sensitivity with and without jitter on each pulse.

Under jittered stimulation conditions, all biCI rats showed very good ITD and ILD sensitivities. After removal of the jitter, rats still showed good ITD and ILD perception albeit with a trend toward reduced sensitivity, indicated by a reduced slope of the psychometric functions at 0 μs ITD and 0 dB ILD.

The results show that ITD and ILD sensitivities of the early-deafened auditory system are not impaired when exposed to jittered pt information during initial training. ITD sensitivity appeared to be comparable under jittered versus unjittered stimulation conditions suggesting that the development of good ITD sensitivity in biCI users does not necessarily require the presentation of microsecond precise ptITDs.

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