gms | German Medical Science

Understanding speech in noisy environments depends on the brain's ability to focus on a target speaker while filtering out background noise. Previous research suggests that musical training enhances this ability through improved auditory processing [1], [2], though the exact neural mechanisms remain unclear. Neural activity in the auditory cortex is known to synchronize with the speech envelope, particularly in the delta (1–4 Hz) and theta (4–8 Hz) frequency bands, which are key to processing speech in challenging listening conditions.

Our study investigates how selective attention and musical training influence cortical speech tracking using magnetoencephalography (MEG). Neural responses were recorded from 52 participants, including musicians and non-musicians, as they targeted one of two competing speech streams. This allowed us to assess the impact of attention and musicianship on speech tracking in the delta and theta bands.

The results showed that selective attention strongly modulates delta-band activity, enhancing neural responses to the targeted speech stream compared to the distracted one. In contrast, theta-band tracking was not significantly affected by attention, indicating its primary role in lower-level acoustic processing, such as parsing syllables, irrespective of attentional focus. This supports prior findings linking delta-band activity to higher-level linguistic processing and comprehension [3].

Surprisingly, musical training did not significantly affect speech tracking in either frequency band. Both musicians and non-musicians displayed similar neural responses to targeted and distracted speech. This challenges previous assumptions that musicianship universally enhances auditory processing, suggesting instead that its effects may be confined to subcortical processing rather than cortical speech tracking. These findings align with studies indicating that musical training primarily improves subcortical sound responses with minimal impact on cortical mechanisms [2].

In summary, our findings emphasize the role of delta-band activity in selective attention during speech perception in noisy environments, while theta-band activity appears to support consistent low-level acoustic processing across conditions. Additionally, the study suggests that musical training does not significantly alter cortical mechanisms of speech tracking, refining our understanding of how musicianship influences auditory processing. These insights advance the knowledge of neural mechanisms underlying speech perception in complex auditory settings. This work has recently been accepted for publication in the Journal of Cognitive Neuroscience [4].