Biology subjects

Commuri, V.

Publications and source records attributed to Commuri, V..

3 recordsLinked to original sources

bioRxiv2026

Neurophysiological Functional Connectivity Changes during Difficult Listening in Older and Younger Adults

Older adults often report increased difficulty understanding speech in noisy listening environments. These difficulties are thought to arise from neurophysiological changes associated with aging, including at the level of cortex. Speech comprehension is believed to rely on coordinated activity across distributed cortical regions, mediated by the directional flow of neural signals - their functional connectivity. This connectivity can be analyzed within specific frequency bands, e.g., Delta and Theta, each thought to play a distinct role in speech and language processing. Here, we utilize the Network Localized Granger Causality (NLGC) framework applied to magnetoencephalography (MEG) data to simultaneously estimate cortical source current activities and the their directed functional connectivity. Whole-brain connectivity graphs were analyzed using graph-cluster enhancement and cluster testing. Temporal Response Functions (TRFs) were obtained by relating NLGC-derived neural current estimates to the speech stimulus presented to listeners. The band-specific networks we identify are consistent with the canonical "dual-stream" model of the auditory processing pathway. Delta-band networks primarily involve temporofrontal connections, whereas Theta-band networks showed stronger temporoparietal connectivity. These cortical networks are shown to evolve as listening conditions become increasingly adverse, incorporating frontoparietal areas associated with attention orienting and control. We find that older adults exhibit increased connectivity within areas of the ventral and dorsal auditory streams across all listening conditions, suggesting increased cortical recruitment to support speech comprehension. Although older adults exhibit enhanced time-locked responses to the speech stimulus, these responses did not significantly coincide with their connectivity patterns (and similarly for younger adults), indicating that their connectivity increases are not explained by central gain mechanisms. Together, our findings demonstrate age- and condition-dependent reorganization of speech-related cortical connectivity across neurophysiological frequency bands.

neuroscience↗

bioRxiv2026

Very Early Cortical Auditory Responses to Speech in Humans

A foundational measure of the auditory systems ability to process sound correctly is the auditory brainstem response (ABR) and middle latency response (MLR) complex, but their dependence on stimulus complexity and behavioral relevance is poorly understood. Here we recorded noninvasive, simultaneous electroencephalography (EEG) and magnetoencephalography (MEG) in adults listening to both naturalistic speech and clicks, and computed the resulting temporal response functions (TRFs). The TRFs ABR-MLR complex for speech listening contains a very early cortical peak (11 ms latency), which has not been well-characterized, and is absent for click stimuli. Other significant differences in latency and source between the speech and click MLR complexes point to further differences in their auditory processing, in thalamus and cortex. In contrast, the speech and click TRFs ABR complex both share a similar, prominent wave V response. In summation, the use of naturalistic speech reveals how early auditory responses reflect its ethological relevance.

neuroscience↗

bioRxiv2023

Cortical Responses Time-Locked to Continuous Speech in the High-Gamma Band Depend on Selective Attention

Auditory cortical responses to speech obtained by magnetoencephalography (MEG) show robust speech tracking to the speakers fundamental frequency in the high-gamma band (70-200 Hz), but little is currently known about whether such responses depend on the focus of selective attention. In this study 22 human subjects listened to concurrent, fixed-rate, speech from male and female speakers, and were asked to selectively attend to one speaker at a time, while their neural responses were recorded with MEG. The male speakers pitch range coincided with the lower range of the high-gamma band, whereas the female speakers higher pitch range had much less overlap, and only at the upper end of the high-gamma band. Neural responses were analyzed using the temporal response function (TRF) framework. As expected, the responses demonstrate robust speech tracking of the fundamental frequency in the high-gamma band, but only to the males speech, with a peak latency of approximately 40 ms. Critically, the response magnitude depends on selective attention: the response to the male speech is significantly greater when male speech is attended than when it is not attended, under acoustically identical conditions. This is a clear demonstration that even very early cortical auditory responses are influenced by top-down, cognitive, neural processing mechanisms.

neuroscience↗