Auditory nerve responses following middle‐ear disarticulation in kittens

Abstract

The effects of partial acoustic deprivation during postnatal development of kittens were studied following the disarticulation of their malleoincal joints. Disarticulations were performed between birth and 10 postnatal days. Prior to 10 postnatal days, auditory thresholds are in excess of 100 dB SPL, and it can be assumed that these animals receive little, if any, acoustic stimulation prior to surgery. Following surgical manipulation of their middle ears, kittens were allowed to grow to adulthood at which time single auditory nerve fibers were studied extracellularly, from both operated and intact sides. Threshold differences between the operated and intact sides confirmed that a conductive lesion had been produced. Other indices of neuronal function, however, showed that most of the fibers from the operated side were normal with respect to their tuning, dynamic range, and phase‐locking ability. There was a slight tendency for fibers on the operated side to exhibit higher than normal spontaneous discharge rates, as well as slightly reduced tip‐to‐tail ratios. Most neurons had normal appearing tuning curves, however, some displayed shallow low‐frequency slopes near their best frequency. In general, middle ear disarticulation did not produce profound effects on auditory nerve responses.