In vivo manganese-enhanced MRI of retinotopic mapping in superior colliculus

Abstract

This study explores the capability of high-resolution 3D Mn-enhanced MRI (MEMRI) for in vivo retinotopic mapping of the rat superior colliculus (SC) upon partial transection of the intraorbital optic nerve. Upon intravitreal Mn2+ injection into both eyes, all animals in Group 1 (n=8) exhibited significantly lower signal intensity in the lateral side of the left SC compared to the left medial SC and right control SC 1 week after superior optic nerve transection in the right eye. Partial transection at other regions of the optic nerve in Group 2 (n=7) led to hypointensity in other regions of the left SC. The results of this study demonstrated the feasibility of high-resolution MEMRI for in vivo, 3D mapping of retinotopic projections in the SC upon reduced anterograde axonal transport of Mn2+ ions at sites of partial transections in the anterior visual pathways. Future MEMRI studies are envisioned that measure the retinotopic changes in normal development, disease, plasticity and therapy in longitudinal studies.