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Cerebral Oxygen Budgeting: Network-Level BOLD Dynamics During Acute Hypoxia.
Daehun Kang1, Koji Uchida2, Clifton R Haider3
1Department of Radiology, Mayo Clinic, MN, 55905.
Biorxiv : the Preprint Server for Biology
|April 10, 2026
Summary
Brain activity changes distinctly under low oxygen. Amplitude of low-frequency fluctuations (ALFF) shows nonlinear modulation, unlike functional connectivity, revealing a cerebral oxygen budgeting strategy.
Area of Science:
- Neuroscience
- Physiology
- Cognitive Science
Background:
- Hypoxia (low oxygen) impairs brain function.
- Hypoxia-responsive functional connectivity (HR-FC) changes rapidly, but its link to local brain activity is unclear.
- Understanding brain's response to oxygen changes is crucial for neurological health.
Purpose of the Study:
- To investigate the relationship between local neurovascular activity and functional connectivity during acute hypoxia.
- To examine dynamic changes in amplitude of low-frequency fluctuations (ALFF) and functional connectivity across brain networks under varying oxygen levels.
- To explore the concept of cerebral oxygen budgeting.
Main Methods:
- Used blood-oxygenation-level dependent (BOLD) fMRI in healthy adults undergoing graded acute hypoxia.
- Measured time-resolved ALFF and functional connectivity using a sliding-window approach.
- Analyzed dynamic changes across large-scale brain networks (Schaefer's 17-network parcellation) during a cognitive task (Go/No-go) with physiological monitoring.
Main Results:
- Severe hypoxia caused temporally dissociated responses: functional connectivity increased monotonically, while ALFF showed nonlinear modulation.
- Distinct network responses observed: Default Mode Network (DefaultA) showed ALFF suppression, while Somatosensory-Motor Network B (SomMotB) was preferentially preserved.
- Network-level ALFF dynamics differed from functional connectivity, indicating structured modulation beyond simple oxygen reduction.
Conclusions:
- Spontaneous BOLD dynamics during hypoxia reflect structured network-level modulation, not just uniform oxygen suppression.
- Amplitude of low-frequency fluctuations (ALFF) provides a complementary view of brain dynamics distinct from functional connectivity.
- Findings support a 'cerebral oxygen budgeting' framework, where metabolic constraints shape brain network function.
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