Neural Coding of Fundamental Frequency and Processing of Discrete Pitch Accents in Middle Age.

Pitch is a prosodic element of speech that speakers dynamically manipulate to convey intention and meaning, making it a powerful cue for spoken language. Neural encoding of fundamental frequency, the primary acoustic cue for pitch, has been shown to deteriorate with age and can occur as early as midlife without overt hearing loss. Here, we systematically examined neural coding of fundamental frequency in middle-aged and young adult listeners using syllabic and naturalistic speech stimuli. We then examined the extent to which neural processing of pitch accents, phonological units of prosody that convey differences in word prominence in naturalistic speech, differed based on age group. Our findings revealed that middle-aged adults exhibited reduced neural coding of fundamental frequency to syllabic and naturalistic stimuli compared with younger adults. Middle-aged adults also demonstrated less distinct neural processing of pitch accents in naturalistic speech, as reflected by greater classification uncertainty in a neural network model classifying pitch accent categories. This finding suggests less specialized cortical processing of suprasegmental prosodic features in the auditory cortex in middle age. Reduced neural coding of fundamental frequency was associated with greater classification uncertainty for pitch accents, linking early auditory deficits to higher order prosodic processing challenges.