Postans, M., Hodgetts, C. J, Mundy, M. E, Jones, D. K, Lawrence, A. D & Graham, KS. (2014). Interindividual variation in fornix microstructure and macrostructure is related to visual discrimination accuracy for scenes but not faces. Journal of Neuroscience,34(36), 12121-12126. United States: Society for Neuroscience. Retrieved from https://doi.org/10.1523/JNEUROSCI.0026-14.2014
Transection of the nonhuman primate fornix has been shown to impair learning of configurations of spatial features and object-in-scene memory. Although damage to the human fornix also results in memory impairment, it is not known whether there is a preferential involvement of this white-matter tract in spatial learning, as implied by animal studies. Diffusion-weighted MR images were obtained from healthy participants who had completed versions of a task in which they made rapid same/different discriminations to two categories of highly visually similar stimuli: ( 1 ) virtual reality scene pairs; and ( 2 ) face pairs. Diffusion-MRI measures of white-matter microstructure [fractional anisotropy ( FA ) and mean diffusivity ( MD )] and macrostructure ( tissue volume fraction, f ) were then extracted from the fornix of each participant, which had been reconstructed using a deterministic tractography protocol. Fornix MD and fmeasures correlated with scene, but not face, discrimination accuracy in both discrimination tasks. A complementary voxelwise analysis using tract-based spatial statistics suggested the crus of the fornix as a focus for this relationship. These findings extend previous reports of spatial learning impairments after fornix transection in nonhuman primates, critically highlighting the fornix as a source of interindividual variation in scene discrimination in humans.
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