Electrophysiological responses to change in spectral ripple envelope phase in normal-hearing infants

Abstract

Spectral resolution plays an important role in understanding speech in noisy real-world listening environments. Spectral ripple discrimination is one method used to measure spectral resolution that has been shown to correlate with open-set speech understanding in adults and children who use cochlear implants. In this study, we investigate the feasibility of obtaining an electrophysiological measure of spectral ripple discrimination in very young infants. Spectral ripple stimuli were constructed from two concatenated 1-s noise carriers consisting of 2555 random phase pure tone frequency components between 100–5000 Hz, with a spectral envelope sinusoidally modulated at 1-ripple-per-ocatave with peak-to-trough depth of 20 dB. The starting phase of the first half of the stimulus varied randomly while the starting phase of the second half was “inverted”, shifted by 90-deg, relative to the first. Infants were presented with 150 repetitions of these stimuli at 80 or 65 dBA in sound field while undergoing 32-channel electroencephalography (EEG) recording. Our preliminary analyses show that an acoustic change response can be recorded in awake infants between 2 and 4 months of age in response to a spectral ripple inversion. These preliminary results suggest the potential utility of EEG in the measurement of spectral resolution in very young infants, warranting further investigation.