Neural tracking of speech in typically listening individuals

Cortical brain oscillations may play important roles in various human cognitive processes. We conducted one of the first EEG studies that tried to identify cortical oscillatory indices across various frequency bands for spoken language processing at different linguistic (phonological and semantic) levels:

Mai, G., Minett, J. W., & Wang, W. S. Y. (2016). Delta, theta, beta, and gamma brain oscillations index levels of auditory sentence processing. NeuroImage, 133:516-528. View publication >> (non-institutional open access here)

Along this line, we further studied predictive coding of speech processing by showing the roles of cortical tracking at different frequency bands may play for neural ‘sharpening’ (neural responses to expected semantic inputs) vs. prediction errors (responses to unexpected semantic inputs):

Figure from Mai & Wang (2023, HBM) (licensed under CC BY-NC 4.0)

Mai, G., & Wang, W. S. Y. (2023). Distinct roles of delta‐ and theta‐band neural tracking for sharpening and predictive coding of multi‐level speech features during spoken language processing. Human Brain Mapping, 44(17):6149-6172. View publication >>

Recent efforts also looked at how cortical tracking of pitch contours indexes effortful listening of speech in noisy environments in typically listening individuals:

Guo, X., Mai, G., Mohammadi, Y., Benzaquén, E., Yukhnovich, K., Sedley, W., & Griffiths, T. D. (2025). Neural entrainment to pitch changes of auditory targets in noise. NeuroImage, 314:121270. View publication >>

‘Frequency-following response’ (FFR) is a subcortical (albeit extra auditory cortical sources) phase-locked response to the speech fundamental frequency, known as a potential index for various hearing and language-related disorders (e.g., hearing loss, developmental dyslexia, autism). We studied a fundamental neuroscientific question in auditory processing in typical listening by looking at how FFR together with low-frequency cortical tracking are affected by day-to-day changes in common psychophysiological status, i.e., the level of arousal/consciousness, across the adult lifespan:

Figure from Mai (2020 PhD thesis) with permission

Mai, G., Schoof, T., & Howell, P. (2019). Modulation of phase-locked neural responses to speech during different arousal states is age-dependent. NeuroImage, 189:734-744. View publication >> (non-institutional open access here)

We also looked at whether changes in neural excitability in the auditory cortex (via neurostimulation tDCS) led to consequential changes in subcortical FFR revealing causal auditory subcortico-cortical interactions. We provided the very first evidence for the causal link between the right hemispheric auditory cortex and subcortical tracking of F0 in human participants:

Figure from Mai & Howell (2022, Cereb Cortex) (licensed under CC BY 4.0)

Mai, G., & Howell, P. (2022). Causal relationship between the right auditory cortex and speech-evoked envelope-following response: evidence from combined transcranial stimulation and electroencephalography. Cerebral Cortex, 32(7):1437-1454. View publication >>