Effect of auditory deprivation on maturation of auditory pathways in the rat

Abstract

To examine the influence of an auditory deprivation on the maturation of the central auditory pathways we reared newborn rats until the age of 21 days in a sound-proof chamber and additionally sutured their pinnae. At the age of 21 days we reopened the outer ear channels and placed the young rats into a normal environment. Every three days we recorded brain stem auditory evoked potentials with clicks, 1-, 8- and 16 kHz tone pulses until the age of 45 days, at the age of 60 days for the last time. Additionally all animals underwent middle latency response audiometry. Only directly after reopening the ear channels the thresholds for 8 and 16 kHz were worse in the deprived animals than in the normal ones. For clicks and 1 kHz and all testings on the other days the mean threshold response of the deprived rats did not differ from that of the normal animals. Testing with clicks, the interpeak latencies (I-IV), that is the brain stem transmission time, were prolonged significantly between the 24th and the 36th day of life. Measuring with 1 kHz tone pulses we found a difference from the 30th to the 36th day. Testing with 8 and 16 kHz tone pulses the brainstem transmission time was significantly prolonged between the 21st and 33rd day of life. The middle latency responses showed large variances, there was no significant difference. After the 36th day of life all latencies had normalised.