COHERENCE ANALYSIS OF ENVELOPE-FOLLOWING RESPONSES (EFRS) AND FREQUENCY-FOLLOWING RESPONSES (FFRS) IN INFANTS AND ADULTS

The frequency-following response (FFR) and the envelope-following resp onse (EFR) were recorded in 1-month-old infants and in adults to exami ne the development of temporal coding. The stimuli were amplitude-modu lated (AM) tones. A modulation frequency of 80 Hz was used in infants; modulation frequencies of 40 and 80 Hz were used in adults. The effec ts of intensity, carrier frequency, and modulation frequency on these responses were studied. Responses were analyzed using magnitude-square d coherence. The effect of intensity on the growth of FFR- and EFR-coh erence were similar in infants and adults. In addition, the growth fun ctions were not affected by the carrier frequency or the modulation fr equency of the stimulus. FFR thresholds did not differ across age grou ps. 'Best frequency' (i.e., infant 80 Hz and adult 40 Hz) EFR threshol ds were the same for infants and adults at 500 and 1000 Hz, but infant EFR thresholds were poorer than adult thresholds at 2000 Hz. Thus, al though FFRs and EFRs are primarily adult-like at 1 month of age, there are some age differences in the EFR that deserve further study.