Cortical Tracking of Continuous Speech Under Bimodal Divided Attention

Area of Science:

• Cognitive Neuroscience
• Auditory Perception
• Neuroscience of Attention

Background:

• Speech processing frequently occurs alongside competing sensory information from other modalities.
• Divided attention between auditory and visual stimuli (bimodal divided attention) may impact how the brain processes speech.
• Understanding these effects is crucial for real-world scenarios like driving while listening.

Purpose of the Study:

• To investigate how bimodal divided attention affects neural processing of continuous speech.
• To determine the impact of varying cognitive load on speech comprehension and neural tracking.
• To identify which levels of speech representation (acoustic to linguistic) are most affected by divided attention.

Main Methods:

• Electroencephalography (EEG) was used to record brain responses.
• Participants performed a visual task with low or high cognitive load while listening to speech.
• Multivariate temporal response function (MTRF) encoding models predicted EEG from speech features.

Main Results:

• High cognitive load in a dual-task significantly reduced speech comprehension accuracy.
• Neural tracking of most acoustic and linguistic speech features remained largely unaffected by increased task load.
• Dual-task conditions selectively reduced neural tracking of some features at later latencies (>200 ms).

Conclusions:

• Behavioral impacts of divided attention on speech processing stem from later cognitive stages, not early sensory impairment.
• Neural mechanisms of crossmodal attention may not affect all speech processing levels uniformly.
• Early neural representations of speech appear robust to divided attention demands.