Selective Auditory Attention Engages Distinct Neural Strategies in Simulated Electric and Acoustic Stimulation Within...

This study aimed to investigate whether electric-acoustic stimulation (EAS) and bimodal stimulation (BS) rely on similar or distinct neural mechanisms to support attention-driven speech comprehension in noisy environments.

This cross-sectional study used electroencephalography to measure cortical multidimensional neural responses and compared them between two groups of young adult normal-hearing listeners (15 subjects per group) exposed to simulated EAS or BS listening conditions in a two-talker competing scene. The simulated stimuli were generated using a vocoder to mimic cochlear implant processing, and low-frequency filtered signals to simulate the residual acoustic hearing provided by hearing aids. Neural indices of selective auditory attention were assessed, including cortical speech tracking accuracy, functional connectivity measured by the weighted phase lag index (wPLI), and cross-frequency phase-amplitude coupling (PAC). Relationships between these neural measures and task-relevant evoked temporal response functions were further examined.

Under both EAS and BS conditions, cortical responses selectively tracked task-relevant speech with comparable accuracy, indicating similar levels of attentional speech encoding. However, the two listening configurations engaged distinct neural coordination mechanisms. EAS was characterized by stronger wPLI, suggesting enhanced phase synchronization across cortical regions, whereas BS exhibited significantly higher theta-alpha and theta-gamma PAC, reflecting increased cross-frequency integration. Importantly, enhanced wPLI in EAS and elevated PAC in BS were both associated with task-relevant-evoked temporal response function activity, indicating configuration-specific neural expression patterns underlying selective attention.

Although EAS and BS achieve comparable cortical speech encoding performance in noisy listening conditions, they engage distinct patterns of cross-frequency coordination for integrating spectrally complementary speech features during auditory object formation. These electroencephalography findings advance the understanding of neural mechanism differences between EAS and BS and provide a neurophysiological foundation for the development of targeted auditory assessment and intervention strategies.