The maturation of frequency selectivity in C57BL/6J mice studied with auditory evoked response tuning curves.

The present study was designed to examine the ontogeny of frequency selectivity in the neonatal auditory system. Mice were tested between 12 and 65 days of age. At each age two measures of auditory sensitivity were made from cochlear nucleus evoked responses. Tone-burst evoked-response thresholds in the quiet were determined for frequencies between 1.0 and 39.0 kHz. A two-tone simultaneous masking procedure was then used to obtain evoked response tuning curves. The frequency selectivity of the tuning curves was quantified by calculating a Q ratio. The results show that tuning is poor in neonates but rapidly improves to adult-like levels within 5-16 days after the inception of auditory function. The data also indicate that the development of frequency selectivity varies directly with the maturation of threshold sensitivity.