Manganese‐enhanced MR imaging (MEMRI) combined with electrophysiology in the study of cross‐modal plasticity in binocularly blind rats

Abstract

Our study aimed to determine and verify the establishment of visual to auditory cross-modal plasticity using manganese-enhanced MR imaging (MEMRI) combined with examinations of the visual evoked potential (VEP), auditory brainstem response (ABR) and bilateral visual cortex response to a bilateral auditory stimulus (AVR). Fourteen healthy male Sprague-Dawley newborn rats were randomly divided into 2 groups (n=7 per group). Optic nerve transection was performed in the 7 rats of Group A three weeks after birth to obtain binocularly blind models, and the 7 rats of Group B were maintained as the control group. The VEP was measured to ensure complete binocular blindness. Four months after the operation, MnCl was injected into the left inner ear perilymph of all rats, and an MRI examination was performed 24h after injection. Then, ABR and AVR were measured to detect the generation of auditory compensatory function. The results of the VEP have confirmed complete binocular blindness. The normalized signal intensity of the bilateral medial geniculate nucleus, auditory cortex, visual center (including the lateral geniculate nucleus, superior colliculus and visual cortex) and right hippocampus in binocularly blind rats was significantly increased compared with that in normal rats (P≤0.005), which was confirmed by measurement of the ABR and AVR. Our results suggested that MEMRI combined with electrophysiology can show changes in the auditory and visual pathways of binocularly blind rats and demonstrate the generation of an auditory compensatory pathway.

Manganese-Enhanced Magnetic Resonance Imaging: Overview and Central Nervous System Applications With a Focus on Neurodegeneration

“…With an increase in detectable projections from both the retina and visual cortex following enucleation, this study demonstrates the ability of MEMRI to not only map the visual system, but also to detect finer neuroplastic changes. Other studies have since demonstrated the ability of MEMRI to detect sensory system-wide neuroplastic changes (Tang et al, 2017a,b).…”

Applications of Manganese-Enhanced Magnetic Resonance Imaging in Ophthalmology and Visual Neuroscience

“…Subsequent studies demonstrated the use of in vivo MEMRI tract tracing for retinotopic mapping at submillimeter resolution (Chan et al, 2011) (Figure 3B), and for monitoring primary versus secondary degeneration after partial transection of the optic nerve (Chan et al, 2017). With these premises, MEMRI can serve as an in vivo imaging model system to evaluate neuroprotective approaches to the injured visual system (Mansergh et al, 2014; Van der Merwe et al, 2016, van der Merwe et al, 2019), as well as to trace neuroplasticity (Immonen et al, 2008; Chan et al, 2012a; Tang et al, 2017b) and regenerated axons along the visual pathway (Liang et al, 2011; Sandvig et al, 2011, 2012; Sandvig and Sandvig, 2014; Komatsu et al, 2017). MEMRI can be combined with diffusion tensor imaging to give complementary information about injury and regeneration in the adult optic nerve (Thuen et al, 2009).…”