In Brief:
This study examined the auditory steady-state responses (ASSRs) evoked by amplitude-modulated (AM), mixed-modulated (MM), and exponentially-modulated (AM2) tones in 50 newborn infants (within 3 days of birth) and in 20 older infants (within 3–15 wk of birth). Multiple ASSRs were evoked by 0.5, 1, 2, and 4 kHz stimuli modulated between 78 and 95 Hz and presented at 50 dB SPL. In newborn infants, responses to MM and AM2 stimuli were 15% larger than AM stimuli (17% larger for older infants). For AM, MM, and AM2 stimuli, the percentage of significant responses was 67%, 73%, 76%, respectively (82%, 82%, 84%, respectively, for older infants). Older infant ASSRs were, on average, 32% larger. In both groups, the percentage of significant responses was decreased due to many 0.5 kHz ASSRs failing to reach significance. Using MM and AM2 stimuli will increase the reliability/efficiency of evoked potential audiometry in infancy. ASSRs at 50 dB SPL are more easily detected at 3–15 wk of age than just after birth. Comprehensive frequency-specific testing of hearing using steady-state responses will likely be more accurate if postponed until after the immediate neonatal period.
