Correlative development of cochlear action potential sensitivity, latency, and frequency selectivity.

The present study was undertaken in order to study the rate of maturation of the cochlear action potential sensitivity, latency, and tuning curves for various stimulus frequencies and to correlate the development of latency and frequency selectivity with threshold development. This study showed a two-stage model of maturation in which thresholds and latencies declined rapidly and linearly during the first stage, and slowly and exponentially during the last stage. These results suggest that latencies and thresholds are influenced by similar maturational processes. The correlative study of frequency selectivity and thresholds showed a linear relationship during the period of rapid maturation, and conversely, a dissociation between the development of tuning and threshold during the late period of slow acquisition of adult sensitivity. This dissociation was particularly marked at 8 kHz where Q10 values continued to increase even when thresholds were adultlike. These results were discussed in relation to anatomical and functional data available from the rat cochlea.