Neural correlates of moderate hearing loss: time course of response changes in the primary auditory cortex of awake guinea-pigs

Abstract

Over the last decade, the consequences of acoustic trauma on the functional properties of auditory cortex neurons have received growing attention. Changes in spontaneous and evoked activity, shifts of characteristic frequency (CF), and map reorganizations have extensively been described in anesthetized animals (e.g., Noreña and Eggermont, 2003, 2005). Here, we examined how the functional properties of cortical cells are modified after partial hearing loss in awake guinea pigs. Single unit activity was chronically recorded in awake, restrained, guinea pigs from 3 days before up to 15 days after an acoustic trauma induced by a 5 kHz 110 dB tone delivered for 1 h. Auditory brainstem responses (ABRs) audiograms indicated that these parameters produced a mean ABR threshold shift of 20 dB SPL at, and one octave above, the trauma frequency. When tested with pure tones, cortical cells showed on average a 25 dB increase in threshold at CF the day following the trauma. Over days, this increase progressively stabilized at only 10 dB above control value indicating a progressive recovery of cortical thresholds, probably reflecting a progressive shift from temporary threshold shift (TTS) to permanent threshold shift (PTS). There was an increase in response latency and in response variability the day following the trauma but these parameters returned to control values within 3 days. When tested with conspecific vocalizations, cortical neurons also displayed an increase in response latency and in response duration the day after the acoustic trauma, but there was no effect on the average firing rate elicited by the vocalization. These findings suggest that, in cases of moderate hearing loss, the temporal precision of neuronal responses to natural stimuli is impaired despite the fact the firing rate showed little or no changes.

Noise-Sensitive But More Precise Subcortical Representations Coexist with Robust Cortical Encoding of Natural Vocalizations

“…Quantification of responses evoked by vocalizations. The responses to vocalizations were quantified using the following two parameters: (1) the firing rate of the evoked response, which corresponds to the total number of action potentials occurring during the presentation of the stimulus minus spontaneous activity; (2) the trial-to-trial temporal reliability coefficient (called CorrCoef, as in our previous studies: Gaucher et al, 2013;Huetz et al, 2014;Gaucher and Edeline, 2015;Aushana et al, 2018), which quantifies the trial-to-trial reliability of the responses over the 20 repetitions of the same stimulus. This index was computed for each vocalization: it corresponds to the normalized covariance between each pair of spike trains recorded at the presentation of this vocalization and was calculated as follows:…”

Assessment of the efficacy of a local steroid rescue treatment administered 2 days after a moderate noise-induced trauma in guinea pig

“…The acoustic trauma delivered in this study was centered on the 5 kHz frequency which usually leads to a threshold shift an octave above the frequency of the traumatic sound [15].…”

Doxepin Mitigates Noise‐induced Neuronal Damage in Primary Auditory Cortex of Mice via Suppression of Acid Sphingomyelinase/Ceramide Pathway

“…Beyond a receiver and processer of auditory sensations, auditory cortex is the most highly organized unit in the brain acting as the neural crux of hearing, language and music. So maladaptation of neurons in this area might cause diversifying and serious outcomes (Huetz et al, ; Lou et al, ), prevention of which is critical for the mitigation of noise induced negative consequences.…”