Electrophysiological Responses to Spectral Ripple Envelope Phase Inversion in 3-Month-Olds and Adults

These findings show a relationship between EEG ACC detection and previously reported behavioral discrimination abilities, with the ACC detected in the 1 RPO but not the 8 RPO condition. These results demonstrate the ACC's potential for infant discrimination threshold estimation because it was elicited by a suprathreshold acoustic change (1 RPO) but not a subthreshold acoustic change (8 RPO). Critically, both 1 RPO and 8 RPO stimuli contained an envelope inversion at 1 sec, suggesting the ACC could serve as an objective measure of stimulus discriminability in infants as young as 3 months. Future studies with more stimulus conditions to fully establish a threshold, online monitoring of responses to increase the success rate of infant testing, and comparison of testing infants awake versus asleep are needed to further develop this approach.