Global waves synchronize the brain's functional systems with fluctuating arousal.

Area of Science:

• Neuroscience
• Systems Neuroscience
• Cognitive Neuroscience

Background:

• Spontaneous fluctuations in functional magnetic resonance imaging (fMRI) signals reflect large-scale brain organization.
• Functional connectivity, derived from these fluctuations, maps brain networks but lacks a unifying physiological explanation.
• Intrinsic brain organization is poorly understood, particularly the mechanisms driving widespread coordination.

Purpose of the Study:

• To propose and empirically support a parsimonious account of brain-wide spatiotemporal organization.
• To investigate the role of traveling waves linked to arousal in spontaneous fMRI signal fluctuations.
• To demonstrate that traveling waves can explain functional connectivity patterns.

Main Methods:

• Utilized functional magnetic resonance imaging (fMRI) in humans to measure spontaneous brain activity.
• Analyzed global waves of activity and their propagation patterns.
• Correlated arousal fluctuations with observed brain activity.
• Measured cortex-wide neural activity propagation using electrocorticography (ECoG) in macaques.

Main Results:

• Ongoing arousal fluctuations correlate with global waves of activity propagating across the neocortex, thalamus, striatum, and cerebellum.
• These traveling waves parsimoniously explain key features of spontaneous fMRI signal fluctuations.
• Traveling waves account for topographically organized functional connectivity.
• Similar cortex-wide neural activity propagation was observed in macaques via ECoG.

Conclusions:

• Traveling waves associated with arousal are a fundamental mechanism for intrinsic brain-wide spatiotemporal organization.
• These waves provide a unifying physiological explanation for spontaneous fMRI signal fluctuations and functional connectivity.
• The findings suggest traveling waves dynamically pattern brain-wide excitability relative to arousal states.