Scalp-recorded frequency-following responses in neonates.

Low-frequency tone bursts (250, 500 and 1 000 Hz) were used to elicit frequency-following responses (FFRs) from full-term, healthy neonates. Easily identifiable FFRs were recorded from all well babies with stimulation at low-to-moderate levels (30-45 dB HLn). The amplitude and threshold values of neonatal FFRs were not significantly different from those of normally hearing adults. As in the adult, neonatal FFRs elicited by tone burst stimuli of 250 and 500 Hz were of greater amplitude and were observed at lower stimulus levels than FFRs recorded at higher frequency stimuli. At stimulus levels of 65 dB HLn, latency to the first peak in the FFR decreased as a function of increasing stimulus frequency. Neonatal FFRs evoked by tone bursts of 250 and 500 Hz exhibited significantly longer latencies compared to FFR recordings obtained from adults. These results suggest that: (1) Low-frequency basilar membrane sensitivity in neonates can be assessed as early as the first day of life. (2) The response properties of the FFR recorded from neonates were similar to the response properties of the FFR recorded from the adult. (3) For infants who fail conventional brainstem-evoked response screening procedures and/or for infants who are born "at risk", the FFR holds great promise as an assessment technique to determine the integrity of the low-frequency-sensitive regions of the cochlea and auditory brainstem.