The influence of the volumetric composition of the intracranial space on neural activity in healthy subjects: a resting-state functional magnetic resonance study

Brain atrophy is a condition observed both with healthy aging and in association with neurologic pathological conditions. We investigated the role of the volumetric composition of the intracranial space (VOCICS) in terms of relative brain volume (BV%) and relative cerebrospinal fluid volume (CSFV%) on the neural activity measured by resting-state functional magnetic resonance imaging (rs-fMRI). We performed a group rs-fMRI analysis of a dataset of 192 healthy subjects derived by the publicly available Functional Connectome Project. Automatic volumetric analysis of structural data was performed in order to obtain BV% and CSFV% for every subject. Two fractional Amplitude of Low-Frequency Fluctuations (fALFF) and two region of interest-to-region of interest (ROI-to-ROI) analyses were then performed using BV% and CSFV% as second-level covariates, adopting a multiple regression statistic test in order to evaluate the effects of BV% and CSFV% on brain networks. The analyses revealed that VOCICS broadly influences brain networks. In conclusion, VOCICS significantly influences brain activity measured by rs-fMRI, and this parameter could represent an easy marker of brain connectivity in healthy young subjects.