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Characterization of the responses of inferior colliculus neurons of the chicken to electrical stimulation of the cochlear nerve

University of British Columbia

Responses of inferior colliculus neurons of the anaesthetized, cochlea-ectomized chicken to electrical stimulation of the cochlear nerves were recorded extracellularly. At least three physiologically distinct cell types were found in the central nucleus of the inferior colliculus. Type 1 fired randomly and with a high spontaneous rate, exhibiting a Poisson distribution in the spike interval histogram. Stimulation of either cochlear nerve produced an inhibition lasting 3 to 46 ms (mean of 16.7, n=16). Type 2 exhibited little or no spontaneous activity, and responded to a short stimulus with a single spike or burst of spikes (n=21). Type 3 exhibited regular, spontaneous firing with preferred intrinsic frequencies in the audio range (n=26), usually resulting in multimodal spike interval histograms. Single pulse stimulation of the contralateral nerve reset the firing rhythm, resulting in periodic post-stimulus time histograms (PSTH). The intermodal interval for a PSTH of a type 3 cell was identical to the intermodal interval for a spontaneous interval histogram. A reverse correlation of a random sequence of stimulus pulses with the response spikes revealed preferred frequencies in the input which were similar to the output frequencies seen in post-stimulus time and interval histograms. Thus, these type 3 neurons exhibited both an oscillatory spontaneous and evoked firing pattern, and an intrinsic frequency selectivity which is presumed to give rise to the observed oscillation. These cells were found to be grouped together in a relatively small portion of the inferior colliculus. The location of several type 3 cells was identified using WGA-HRP injected from the recording electrode. These cells were found to be in the core of the central nucleus of the inferior colliculus. These findings suggest the existence of an intrinsic mechanism for frequency filtering and time coding in the CNS.

Thesis/Dissertation

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2009-03-06

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http://hdl.handle.net/2429/5687

Physiology

University of British Columbia

UBCV

DSpace