Diffusivity and kurtosis time-dependence changes in the rat brain during somatosensory evoked response

Motivation: The microstructure-function relationship is essential for our understanding of the healthy and pathological human brain. Goal(s): In this context, the goal of our study was to investigate microstructural changes arising in the brain during neuronal activity. Approach: Differences in mean diffusivity MD and mean kurtosis MK time-dependence between rest and active states were assessed in the somatosensory cortex following rat forepaw stimulation. Results: While no changes were found in control cortical regions, the BOLD-fMRI positive cluster presented a significant decrease in MD and MK during activation. Interestingly, subcortical somatosensory relays displayed the opposite trend which could result from changes in inhibitory/excitatory balance. Impact: Neuronal activity is accompanied by a myriad of microstructural changes. The diffusion-weighted signal sensitivity to underlying brain microstructure brings new perspectives into the structure-function relationship along with the promise of a functional contrast unbound from the current limitations of BOLD-fMRI.