title: White-matter diffusion fMRI of mouse optic nerve.
abstract: Non-invasive assessment of white-matter functionality in the nervous system would be a valuable basic neuroscience and clinical diagnostic tool. Using standard MRI techniques, a visual-stimulus-induced 27% decrease in the apparent diffusion coefficient of water perpendicular to the axonal fibers (ADC(perpendicular)) is demonstrated for C57BL/6 mouse optic nerve in vivo. No change in ADC(||) (diffusion parallel to the optic nerve fibers) was observed during visual stimulation. The stimulus-induced changes are completely reversible. A possible vascular contribution was sought by carrying out the ADC(perpendicular) measurements in hypercapnic mice with and without visual stimulus. Similar effects were seen in room-air-breathing and hypercapnic animals. The in vivo stimulus-induced ADC(perpendicular) decreases are roughly similar to literature reports for ex vivo rat optic nerve preparations under conditions of osmotic swelling. The experimental results strongly suggest that osmotic after-effects of nerve impulses through the axonal fibers are responsible for the observed ADC decrease.
authors.affiliation: Biomedical MR Laboratory, Department of Radiology, Washington University School of Medicine, St Louis, MO 63110, USA. spees@wustl.edu
authors.forename: William M
authors.initials: WM
authors.lastname: Spees
authors.forename: Tsen-Hsuan
authors.initials: TH
authors.lastname: Lin
authors.forename: Sheng-Kwei
authors.initials: SK
authors.lastname: Song
mesh_terms: D000818:Animals; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D051379:Mice; D008810:Mice, Inbred C57BL; D009900:Optic Nerve / Q000502:physiology*; D010775:Photic Stimulation