Exploring simultaneous assessment of cortical and subcortical entrainment to ongoing speech

Human speech processing relies on fine temporal coding at the level of the auditory brainstem as well as at cortical stages. Tonal languages in particular rely on accurate coding of pitch, and speakers of tonal languages may have specialized pitch-related processing at both cortical and subcortical levels. However, responses at these two stages are typically investigated separately, and using different stimuli. Subcortical responses are traditionally assessed with repetitions of short, simple stimuli such as single syllables, while cortical processes can be probed with ongoing speech. Recent studies have shown that subcortical responses can also be measured with ongoing speech stimuli, using regularized regression or cross-correlation approaches. This suggests the prospect of simultaneously observing the processing of the same ongoing speech stimuli at cortical and brainstem level. The present study explores this possibility, with the perspective of examining how temporal cues in tonal languages are processed along the auditory pathway, and how this may be affected by hearing loss.