Experimental Brain Research

, Volume 153, Issue 4, pp 436–442 | Cite as

Effects of intensity of repetitive acoustic stimuli on neural adaptation in the ventral cochlear nucleus of the rat

Research Article

Abstract

To study neural adaptation as a function of stimulus intensity, auditory near-field evoked potentials were recorded from the ventral cochlear nucleus in awake Long Evans rats. Responses to 250-ms trains of repetitive clicks (pulse rates ranging from 100 to 1000 pulses per second) were collected at stimulus intensities of 5, 10, 30, 50 and 70 dB SPL. The amplitude of the first negative (N1) component of the average evoked potentials to individual pulses in the train was measured by using a subtraction method. The N1 responses were normalized with respect to the highest cochlear nucleus potential observed in the train, and then plotted as a function of click position in the train. As expected, the general trend of the curves was an exponential decay reaching a plateau more or less rapidly as a function of both intensity and rate of stimulation. Fitting these curves with exponential decay equations revealed that the rapid time constant decreased for increasing stimulus intensities whereas the short-term time constant is relatively independent of intensity. The amount of adaptation (expressed as the ratio of the plateau to the first peak amplitude) was substantially less prominent at low intensities (5–10 dB SPL) and low rates (100–200 pulses per second) than at higher intensities and high rates. These results indicate that adaptation patterns obtained in the ventral cochlear nucleus by using near-field evoked potentials exhibit properties comparable to those already present at the level of the auditory nerve.

Keywords

Unanesthetized Brainstem Auditory evoked potentials Click 

Notes

Acknowledgements

The authors would like to thank B. Aebischer, E. Regli and A. Gaillard for their technical assistance, F. Tinguely for the histology, and J. Corpataux and B. Morandi for taking care of the rats in the animal room. This research project was supported by the Swiss National Science Foundation (Grant no. 32-56352.99; TANDEM) and the National Center for Competence in Research (NCCR) “Neural Plasticity and Repair”.

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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  1. 1.Division of Physiology, Department of MedicineUniversity of FribourgFribourgSwitzerland

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