Imaging hypothalamic activity using diffusion weighted magnetic resonance imaging in the mouse and human brain

► DWI identifies hypothalamic activation by fasting in mice and humans. ► Increases in diffusion parameters can be observed in subhypothalamic nuclei. ► Fisher analysis discriminates DWI from fed and fasted states in mice and humans. ► Increases in diffusion may reveal osmotic changes associated with neuronal firing. ► DWI provides a useful tool to evaluate hypothalamic performance.