Arousal modulates functional connectivity through structured and hemispherically asymmetric community architecture...

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Brain Imaging

Background:

• Arousal levels naturally vary during wakefulness.
• The impact of these moment-to-moment arousal changes on large-scale brain functional connectivity (FC) is not well understood.

Purpose of the Study:

• To investigate how spontaneous fluctuations in arousal influence time-varying functional connectivity in the awake human brain.
• To characterize the network organization shaped by arousal modulation.

Main Methods:

• Utilized ultra-high field (7T) functional Magnetic Resonance Imaging (fMRI) combined with concurrent pupillometry.
• Quantified the covariance between time-varying FC and spontaneous arousal for individual functional connections.

Main Results:

• Arousal organized the brain's connectome into seven distinct connectivity communities, rather than a uniform influence.
• Identified systematic hemispheric asymmetries, including a 'left-hemisphere centripetal architecture' where the left hemisphere acts as a convergence point for arousal-modulated signals.
• This modular and asymmetric organization remained stable during naturalistic movie watching, suggesting generalizability.

Conclusions:

• Moment-to-moment arousal fluctuations significantly shape large-scale functional connectivity in the awake brain.
• Arousal-related modulation of FC is characterized by a structured, low-dimensional, and hemispherically asymmetric network organization.
• These findings highlight intrinsic organizational principles of the brain that generalize across different cognitive contexts during wakefulness.