Acoustic basis of context dependent brainstem encoding of speech.

The newfound context dependent brainstem encoding of speech is evidence of online regularity detection and modulation of the sub-cortical responses. We studied the influence of spectral structure of the contextual stimulus on context dependent encoding of speech at the brainstem, in an attempt to understand the acoustic basis for this effect. Fourteen normal hearing adults participated in a randomized true experimental design in whom brainstem responses were recorded. Brainstem responses for a high pass filtered /da/ in the context of syllables, that either had same or different spectral structure were compared with each other. The findings suggest that spectral structure is one of the parameters which cue the context dependent sub-cortical encoding of speech. Interestingly, the results also revealed that, brainstem can encode pitch even with negligible acoustic information below the second formant frequency.

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