Resting-state functional connectivity MRI (rs-fcMRI) can be reliably performed in mice, producing high-resolution whole-brain images. The functional connections strongly align with the brain's structural wiring, as mapped by anterograde tracer studies. Large-scale network properties previously seen only in primates also exist in rodents, though with some differences. A potential default mode network (DMN)—a system important for social cognition and disrupted in many disorders—was identified in the mouse brain both structurally and functionally. These findings validate mouse rs-fcMRI as a translational bridge, allowing stronger links between cellular and molecular manipulations in mice and human brain conditions.
A single high dose of psilocybin (25 mg) massively disrupts functional connectivity in the human brain, causing more than threefold greater change than methylphenidate (40 mg). These changes are driven by desynchronization across spatial scales, dissolving network distinctions by reducing correlations within and anticorrelations between networks. The strongest effects occur in the default mode network, which is connected to the anterior hippocampus and is thought to create the sense of space, time, and self. Individual differences in connectivity changes are strongly linked to the subjective psychedelic experience. A persistent decrease in connectivity between the anterior hippocampus and default mode network lasts for weeks, suggesting a neuroanatomical correlate of the therapeutic and proplasticity effects of psychedelics.
Metastability of BOLD fMRI signals, a proxy for brain dynamics, shows within-subject reliability comparable to static functional connectivity when enough data are used, but the amount needed varies across brain networks. Combining network-specific metastability metrics into a single feature vector improves reliability by an order of magnitude. This finding was reproduced in the Midnight Scan Club dataset (10 subjects over 10 days). The measure also proved sensitive to change in brain dynamics under psilocybin. The authors conclude the combined feature vector is a promising candidate for individual-specific biomarkers and precision neuromodulation targets.