Time course of EEG complexity reflects attentional engagement during listening to speech in noise

Distraction caused by auditory noise poses a considerable challenge to the quality of information encoding in speech comprehension. The aim of this study was to explore the temporal dynamics and complexity of electroencephalog-raphy (EEG) microstates in relation to attentional engage-ment over time, contributing to the understanding of speech perception in noise. We examined three listening condi-tions: speech perception with background noise, focused attention on the background noise, and intentional disre-gard of the background noise. Our findings revealed an increase in complexity during the transition of microstates and a slower microstate recurrence when individuals directed their attention to speech compared to tasks without speech. Additionally, a two-stage time course for both microstate complexity and alpha-to-theta power ratio was observed. Specifically, in the early epochs, a lower level was observed, which gradually increased and eventually reached a steady level in the later epochs. The findings suggest that the ini-tial stage is primarily driven by sensory processes and infor-mation gathering, while the second stage involves higher-level cognitive engagement, including mnemonic binding and memory encoding. ### Competing Interest Statement The authors have declared no competing interest. * ACC : Anterior Cingulate Cortex BA : Background Attended BA-MT : Background Attended in Multitalker noise BUA : Background Unattended BUA-MT : Background Unattended in Multitalker noise dBA : A-weighted Decibels DMN : Default Mode Network EEG : Electroencephalography FT : Fluctuating Traffic noise GAMM : Generalized Additive Mixed Model GFP : Global Field Power GMD : Global Map Dissimilarity GLMM : Generalized Linear Mixed Model HW : Highway noise iEEG : Intracranial Electroencephalography KL : Krzanowski-Lai criterion LA : Lecture Attended LA-FT : Lecture Attended in Fluctuating Traffic noise LA-HW : Lecture Attended in Highway noise LA-MT : Lecture Attended in multitalker noise LA-PK : Lecture Attended in Pink noise LC-NE : Locus Coeruleus-Norepinephrine LOI : Line of Interest MCI : Mild Cognitive Impairment MT : Multitalker Noise MRI : Magnetic Resonance Imaging OAE : Otoacoustic Emission OFC : Orbitofrontal Cortex PCC : Posterior Cingulate Cortex PK : Pink noise RQA : Recurrence Quantification Analysis RSN : Resting State Network TFR : Time-Frequency Representation t-SNE : t-Distributed Stochastic Neighbor Embedding WM : Working Memory