Using Diffusion Tensor Imaging to Investigate How Brain Derived Neurotrophic Factor Genotype Influences Thalamo-Cortical Tracts

Abstract

A single nucleotide polymorphism (SNP) in the gene coding for brain derived neurotrophic factor (BDNF) has previously been associated with variations in memory performance, learning ability, and hippocampal volume in humans. However, relatively little is known about the effects this polymorphism might have on connectivity via white matter pathways within the brain. Diffusion tensor imaging (DTI) has repeatedly been argued to be a valid method for investigating the integrity of white matter microstructure in vivo. Two thalamocortical tracts have been suggested to be particularly important to recognition memory. Here therefore, using probabilistic tractography on DTI-derived data, we compared the integrity of thalamo-cortical tracts in Val homozygotes and Met+ allele carriers of the BDNF gene. Participants also completed the visual memory subsets of the Wechsler Memory Scale-3rd edition (WMS-III). We found reduced connectivity in Met allele carriers, as measured by fractional anisotropy (FA) and mean diffusivity (MD), in thalamo-cortical tracts seeded from the anterior and medial dorsal thalamic nuclei. However, no difference was found in performance on recognition memory tasks.