Influence of auditory experience on the development of brain stem auditory-evoked potentials in mallard duck embryos and hatchlings.

The development of brain stem auditory-evoked potentials (BAEP) was studied in devocalized ducklings reared in auditory isolation and in vocal ducklings exposed to enhanced species-specific auditory stimulation with embryonic contact-contentment calls (CTs). Thresholds and latency of BAEP wave P1 in the mute ducklings indicated that even short-term auditory deprivation affected the development of auditory sensitivity, substantially reducing the rate of decline in BAEP thresholds and latencies of P1, especially in the low-frequency (500 and 750 Hz) and high-frequency (above 2.0 kHz) ranges. The ducklings exposed to enhanced stimulation, on the other hand, showed an accelerated decline in BAEP thresholds and latencies of P1 across all test frequencies, with the most marked influence on low (below 1.5 kHz) and high (above 2.5 kHz) frequencies. The influence of species-specific auditory experience had its most potent effect during the embryonic critical period for postnatal auditory perceptual (behavioral) development, at which time the embryo produces and hears a special low-frequency (1.5-2.5 kHz) version of its own contact-contentment vocalization.