The corpus callosum (CC) is the major pathway for interhemispheric communication and a primary target of white-matter neurodegenerative diseases. Diffusion MRI is widely used to assess white-matter structural alternations in diseases. In addition to morphological changes, we previously demonstrated the feasibility to assess white matter function using diffusion MRI. We observed a 27% perpendicular apparent diffusion coefficient (ADC⊥) decrease in normal mouse optic nerve during visual stimulation. In the current study, we implanted MR-compatible tungsten wires at primary somatosensory cortex and observed 15 – 21% ADC⊥ decrease in CC, suggesting diffusion MRI can be applied to study function at this site.