Noninvasive high field MRI brain imaging of the garter snake (Thamnophis sirtalis)

This report documents the application of high held magnetic resonance imagi ng to viewing the central nervous system of garter snakes (12-43 g) with em phasis on the vomeronasal and olfactory systems. Slices in all three planes were taken in lightly sedated snakes showing many major neural structures with resolution down to less than 60 mu m. The images were obtained as 8 or 16 serial slices with slice spacings of 0.25 mm and 0.25 mm thick and were processed to a 256 x 256 matrix with a field of view (FOV) of 14 or 25 mm. The vomeronasal organs, main and accessory olfactory bulbs, telencephalon, cortex, tectum, medulla, cerebellum, spinal cord, and other major features of the brain are clearly defined in the images. The value of noninvasive n eural imaging in comparative and experimental studies of squamate reptiles will become increasingly recognized as the technology is further developed but can be effectively employed at present.