Direct comparison between properties of adaptation of the auditory nerve and the ventral cochlear nucleus in response to repetitive clicks

Abstract

The present study was designed to complete two previous reports [Loquet, G., Rouiller, E.M., 2002. Neural adaptation to pulsatile acoustical stimulation in the cochlear nucleus of the rat. Hear. Res. 171, 72-81;Loquet, G., Meyer, K., Rouiller, E.M., 2003. Effects of intensity of repetitive acoustic stimuli on neural adaptation in the ventral cochlear nucleus of the rat. Exp. Brain Res. 153, 436-442] on neural adaptation properties in the auditory system of the rat. Again, auditory near-field evoked potentials (ANEPs) were recorded in response to 250-ms trains of clicks from an electrode chronically implanted in the ventral cochlear nucleus (VCN). Up to now, our interest had focused on the adaptive behavior of the first one (N 1 ) of the two negative ANEP components. A re-examination of our data for the second negative component (N 2 ) was now undertaken. Results show that the adaptation time course observed for N 2 displayed the same three-stage pattern previously reported for N 1 . Similarly, adaptation became more pronounced and occurred faster as stimulus intensity and/or repetition rate were increased. Based on latency data which suggest N 1 and N 2 to be mainly due to the activity of auditory-nerve (AN) fibers and cochlear nucleus neurons, respectively, it was concluded that neural adaptation assessed by gross-potentials was similar in the AN and VCN. This finding is meaningful in the context of our search to restore normal adaptation phenomena via electro-auditory hearing with an auditory brainstem implant on the same lines as our work in cochlear implants.

The adaptive pattern of the late auditory evoked potential elicited by repeated stimuli in cochlear implant users

“…In CI users, the main source of neural adaptation/refractoriness would come from the retrocochlear portion of the auditory system because the electrode bypasses the damaged cochlea (Litvak et al, 2003;Loquet et al, 2004;Meyer et al, 2007;Zhang et al, 2007). Our study cannot determine whether both adaptation and refractoriness have contributed to the LAEP amplitude reduction in response to stimulus repetition.…”

Neural Adaptation and Behavioral Measures of Temporal Processing and Speech Perception in Cochlear Implant Recipients

“…First, it is possible that there is an interaction of the effects of stimulus parameters on different measures. Gap-detection thresholds depend on stimulus intensity in both acoustic and electric conditions and the adaptation of both ECAP/LAEP can also be affected by stimulus intensity [57, 65, 66]. Although we presented stimuli at the most comfortable listening level for all tests, the stimulus intensity corresponding to their most comfortable listening levels may be different within the dynamic range for subjects.…”

The Time Course of the Amplitude and Latency in the Auditory Late Response Evoked by Repeated Tone Bursts

“…The auditory nerve fiber in deafened ears without functional hair cell synapses exhibit adaptation when presented with electrical stimuli, suggesting that the auditory nerve fiber membrane property provides another source of adaptation in the auditory periphery (Litvak et al, 2001;Zhang et al, 2007). Compared to peripheral stages, the central neurons display additional and possibly greater local adaptation (Loquet et al, 2004;Meyer et al, 2007). Because adaptation of evoked responses recorded along the auditory pathway in animals appears to be more pronounced as the response generator is at more central levels, the adaptation of the ALR observed in the current study might reflect a combination of the Figure 6.…”