Altered Evening Aperiodic Activity and Microstate Dynamics in Insomnia Disorder: An OPM MEG Study

Area of Science:

• Neuroscience
• Sleep Medicine
• Computational Neuroscience

Background:

• Insomnia disorder (ID) is linked to hyperarousal, but its large-scale network dynamics across the sleep-wake cycle are not well understood.
• Previous fMRI studies show network alterations in ID, yet lack high-temporal-resolution data.
• Characterizing cortical excitability and network dynamics in ID requires advanced neuroimaging techniques.

Purpose of the Study:

• To investigate the relationship between cortical excitability and large-scale network dynamics in insomnia disorder.
• To characterize temporal-spatial alterations in brain networks across the sleep-wake cycle in ID.
• To explore the electrophysiological signatures of insomnia using OPM-MEG.

Main Methods:

• Eyes-closed resting-state OPM-MEG recordings in 26 ID patients and 29 controls during evening and morning sessions.
• Analysis of the aperiodic spectral exponent for cortical excitability and microstate analysis for network dynamics.
• Mediation analysis to link electrophysiological features with subjective sleep quality.

Main Results:

• ID patients showed a flatter aperiodic power spectrum (elevated cortical excitability) in the evening compared to controls.
• Distinct microstate alterations included an evening-specific increase in a temporal-limbic microstate and sustained sensorimotor microstate elevation.
• Altered evening limbic microstate dynamics mediated the link between aperiodic exponent and sleep disturbance.

Conclusions:

• Insomnia disorder features concurrent disruptions in neural activity and microstate temporal organization.
• Distinct diurnal profiles of sensorimotor and limbic network alterations are observed in ID.
• OPM-MEG effectively captures the complex electrophysiological characteristics of insomnia.