Graded hypergravity is associated with large-scale reorganization of resting-state cortical networks: EEG evidence from a neurological inactivity phenotype.

Background: Chronic physical inactivity and reduced sensorimotor engagement are associated with alterations in large-scale brain network organization, often reflected as changes in resting-state functional connectivity. Interventions capable of modulating multisensory input without requiring volitional movement may therefore provide a useful experimental framework for investigating inactivity-related cortical plasticity. Short-arm human centrifugation (SAHC) delivers controlled, intermittent graded hypergravity, providing a reproducible vestibular-somatosensory stimulus with potential neuromodulatory effects on cortical networks. Methods: In this exploratory pilot study, resting-state electroencephalography (EEG) was recorded before and after repeated SAHC exposure in a neurological inactivity cohort predominantly comprising individuals with multiple sclerosis. EEG signals were reconstructed at the cortical source level using standardized low-resolution electromagnetic tomography (sLORETA) and parcellated into 148 cortical regions. Functional connectivity was estimated using synchronization likelihood, and large-scale network organization was characterized using graph-theoretical analysis. Network-Based Statistics (NBS) was applied to identify statistically significant pre-post connectivity differences. Results: Following repeated exposure to graded hypergravity, 1333 cortical connections exhibited statistically significant changes, all reflecting reductions in resting-state functional connectivity. These effects were distributed across widespread cortical regions, indicating large-scale network reorganization rather than focal modulation. The intervention was well tolerated, and no serious adverse events were reported. Conclusions: Graded hypergravity delivered via short-arm human centrifugation was associated with widespread reorganization of resting-state cortical functional networks in a phenotype of prolonged inactivity. The observed reductions in functional connectivity are consistent with adaptive network reconfiguration. These findings suggest that controlled multisensory gravitational stimulation can modulate large-scale cortical network organization under conditions of prolonged inactivity. Given the small and heterogeneous pilot cohort, these findings should be considered exploratory and hypothesis-generating.