Conditioning and reflex modification of the rabbit nictitating membrane response using electrical stimulation in auditory nuclei

Electrical brain stimulation (EBS) was applied to four nuclei in the audito ry system, namely, the cochlear nucleus (CN), superior olive (SO), inferior colliculus, and medial geniculate. EBS was also applied to the pontine nuc lei, which are the main relays for transmitting auditory conditioned stimul i (CSs) into the cerebellar pathways for conditioning of the nictitating me mbrane response (NMR). EBS of the CN, but no other site, yielded reflex mod ification, which was an increase in the unconditioned NMR to an airpuff unc onditioned stimulus (US) when preceded by EBS. Throughout the experiment, E BS of the SO produced a distinctive distribution of NMRs, in which a high p roportion had latencies less than 50 ms. When EBS was repeatedly paired wit h the airpuff US, conditioned responses (CRs) were acquired to comparable l evels across all sites. At each site, response likelihood was an increasing function of the EBS parameters of pulse amplitude, pulse frequency, and pu lse width. Combined with anatomical findings, these results indicate that m ultiple encodings of an auditory CS are sent to the pathways for the NMR. ( C) 1999 Elsevier Science B.V. All rights reserved.