Middle components of the auditory evoked potentials in infants.

Middle components of the averaged auditory evoked potentials (AEP) were recorded from 18 infants, 6 each at one, four and eight months of age, during natural sleep, Tone bursts centered at 1000 Hz were presented from a loudspeaker at 15, 30, 45 and 60 dB HL (re: normal adult tone burst threshold). In addition, an equal duration no stimulus control AEP was also obtained. Each averaged response consisted of the sum of 400 stimuli presented at a rate of about 6/sec. Latencies and amplitudes of the three peaks, Na, Pa and Nb, were analyzed as a function of age and intensity. There were no significant differences in latency as a function of age, and only peak Pa showed a significant increase in amplitude as a function of increasing age. The latency of peak Pa decreased significantly as a function of intensity, while the amplitude of all three peaks showed significant differences as a function of intensity. Judges' scores of the presence of responses showed that at 60 dB HL, all infants yielded patterns which were scored as "response present." Smaller percentages of "response present" were scored for the successively lower intensity levels. The results from the 18 infants in this study were similar to those obtained from six normal, sleeping adults tested under identical stimulating and recording conditions in this laboratory.