Ultra-fine temporal resolution in auditory processing is preserved in aged mice without peripheral hearing loss

Age-related hearing loss (presbycusis) is caused by damage to the periphery as well as deterioration of central auditory processing. Gap detection is a paradigm to study age-related temporal processing deficits, which is assumed to be determined primarily by the latter. However, peripheral hearing loss is a strong confounding factor when using gap detection to measure temporal processing. In this study, we used mice from the CAST line, which is known to maintain excellent peripheral hearing, to rule out any contribution of peripheral hearing loss to gap detection performance. We employed an operant Go/No-go paradigm to obtain psychometric functions of gap in noise (GIN) detection at young and middle age. Besides, we measured auditory brainstem responses (ABR) and multiunit recordings in the auditory cortex (AC) in order to disentangle the processing stages of gap detection. We found detection thresholds around 0.6 ms in all measurement modalities. Detection thresholds did not increase with age. In the ABR, GIN stimuli are coded as onset responses to the noise that follows the gap, strikingly similar to the ABR of noise bursts in silence (NBIS). The simplicity of the neural representation of the gap together with the preservation of detection threshold in aged CAST mice suggests that GIN detection in the mouse is primarily determined by peripheral, not central processing.