Kevin C. Chan1,2, Iris Y. Zhou1,2, Shu juan Fan1,2, Joe S. Cheng1,3, Ed X. Wu1,2
1Laboratory of Biomedical Imaging & Signal Processing, the University of Hong Kong, Pokfulam, Hong Kong, China, People's Republic of; 2Department of Electrical & Electronic Engineering, the University of Hong Kong, Pokfulam, Hong Kong, China, People's Republic of; 3Department of Electrical & Electronic Engineering, the Univrsity of Hong Kong, Pokfulam, Hong Kong, China, People's Republic of
This study explores the capability of high-resolution Mn-enhanced MRI (MEMRI) for in vivo assessment of the reorganization of retinocollicular projections between retina and the superficial layers of superior colliculus (SC) in rat models of early postnatal visual impairments. Eight weeks after neonatal monocular enucleation (ME, n=6) to the right eyes at postnatal day (P) 1, intravitreal Mn injection into the left eyes resulted in a significantly higher T1-weighted signal intensity in the ipsilateral left SC compared to the monocularly deprived (MD, right eye, n=6) or normal control (CTRL, n=6) rats at the same age. No significant difference was observed in the Mn-enhancement in contralateral right SC among ME, MD and CTRL groups. Complementary DTI findings suggested neurodegeneration in the right optic nerve and left optic tract of the ME rats, whereas a higher fractional anisotropy was observed in the left optic nerve of the ME rats compared to MD or CTRL rats. The results of this study demonstrated the sensitivity of in vivo MEMRI to detect neural plasticity of the uncrossed retinal projections in SC globally at high resolutions.