Assessing the effects of dendritic spines plasticity using structural MRI on mice

Changes in the structure of synaptic connections underlie various physiological and neurological processes ranging from the development of new synapses and neuronal circuitry related to learning and memory processes to neural plasticity after injury and recovery. Recent technological advances, including two-photon microscopy and transgenic mice overexpressing fluorescent proteins have made possible to image individual dendritic arbors and spines in cortex in living animals. However, it is difficult to obtain an analysis of the effects of synaptic plasticity in the entire brain by two-photon microscopy imaging. The aim of this work is to assess the detectability of such fine structural changes induced by Cytotoxic necrotizing factor 1 (CNF1) via diffusion weighted Magnetic Resonance Imaging (dMRI). In this preliminary work, classical Diffusion Tensor Imaging (DTI)-based indices were derived for two groups of mice (five controls and eight CNF1-treated) and group differences were assessed by statistical analysis. T2-based Voxel Based (VBM) and Tensor Based Morphometry (TBM) were used for benchmarking. Results highlight an increment in Fractional Anisotropy (FA) and a decrement of both Mean (MD) and Radial Diffusivity (RD) mainly in the visual and hippocampal areas. Even though statistical significance was not reached, this demonstrates DTI sensitivity to the effects of synaptic modifications. Our data suggest that mouse morphoanatomical imaging is sensitive to changes in neural plasticity. We are now planning to corroborate these preliminary results on a larger cohort of animals