Can Single Shell Diffusion MRI Detect Synaptic Plasticity in Mice?

Abstract

Changes in the structure of synaptic connections underlie various physiological and neurological processes such as the development of new synapses and neuronal circuitry related to learning and memory processes or 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. The aim of this work is to assess the detectability of such fine structural changes induced by Cytotoxic necrotizing factor 1 (CNF1) also 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 (twelve controls and fifteen 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 of both Fractional Anisotropy (FA) and Axial Diffusivity (AD) and a decrement of both Mean Diffusivity (MD) and Return To Plane Probability (RTPP) mainly in the visual and hippocampal areas. Our data suggest that mouse morphoanatomical imaging is sensitive to changes in neural plasticity.1