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 reducting 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.