MRI-detectable hippocampal volume changes associated with CA1 dendritic growth and branching in adult mice following environmental enrichment

Motivation: Human MRI studies have reported structural brain plasticity under various intervention protocols. Goal(s): However, the underlying cellular mechanisms behind MRI-detectable volume changes remain unknown. Approach: Here we performed in vivo MRI studies in adult mice that experienced environmental enrichment where the larger-sized home cage was equipped with running wheels, toys, tunnels, ladders, and nesting materials. Results: Longitudinal deformation-based morphometry analysis revealed significant volume increases in the dorsal hippocampus of the enrichment group compared with the standard home cage group. Post-mortem Golgi staining analysis from the same subjects revealed significant increases in the dendritic branching and length in the hippocampal CA1 neurons. Impact: Combined MRI and histology study in adult mice revealed the causal relationship between MRI-detectbale volume changes and changes in neuronal morphology. These results provide microscopic interpretations of human MRI studies that have reported structural brain plasticity under various intervention protocols.