Development of cochlear function in the ear of the infant rat.

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Abstract
Using the cochlear potential method, development of auditory sensitivity for pure tones was traced in 3 litters of rats. 1st responses at 8-9 days of age were followed by progressive improvements in sensitivity and range of frequencies to which Ss [subjects] responded until adult sensitivity was reached at 16-20 days. Peak sensitivity increased by 125 db. and range of frequencies expanded from 200-2,000 cps to 100-70,000 cps in a typical litter. Additional measurements established the form of the curve relating maximum output to frequency in infants and assessed the relative role in growth of sensitivity played by the opening of the meatus at 12-13 days of age.