AUDITORY THRESHOLD-SENSITIVITY OF THE HUMAN NEONATE AS MEASURED BY THE AUDITORY BRAIN-STEM RESPONSE

The absolute auditory sensitivity of the human newborn infant was inve stigated using auditory brainstem response thresholds (ABR). ABRs were elicited with clicks and tone-bursts of 0.5, 1.5, 4.0 and 8.0 kHz, em bedded in notched noise, in healthy, full-term human neonates and youn g adults with known, normal-hearing sensitivity. Stimuli were calibrat ed using a probe microphone positioned near the tympanic membrane in t he ear canal of each subject to control for differences in resonance c haracteristics of infant and adult ear canals. ABR thresholds were als o characterized relative to group psychophysical thresholds (nHL) and relative to individual psychophysical threshold or sensation level (SL ) for the adult subjects. infant ABR thresholds measured in p.e. SPL f or all stimuli are elevated by to 3-25 dB relative to adult thresholds . Threshold elevation is greatest for the high-frequency stimuli. Resu lt are consistent with neural immaturity for high-frequency stimuli in the auditory system of human neonates.