Cross-phaseogram: objective neural index of speech sound differentiation.

We introduce a new approach, the cross-phaseogram, that captures the brain's ability to discriminate between spectrotemporally dynamic speech sounds, such as stop consonants. The goal was to develop an analysis technique for auditory brainstem responses (ABRs) that taps into the sub-millisecond temporal precision of the response but does not rely on subjective identification of individual response peaks. Using the cross-phaseogram technique, we show that time-varying frequency differences in speech stimuli manifest as phase differences in ABRs. By applying this automated and objective technique to a large dataset, we found these phase differences to be less pronounced in children who perform below average on a standardized test of listening to speech in noise. We discuss the theoretical and practical implications of our results, and the extension of the cross-phaseogram method to a wider range of stimuli and populations.