Short-Term Learning Induces White Matter Plasticity in the Fornix

Abstract

Magnetic resonance imaging (MRI) has greatly extended the exploration of neuroplasticity in behaving animals and humans. Imaging studies recently uncovered structural changes that occur in gray and white matter, mainly after long-term training. A recent diffusion tensor imaging (DTI) study showed that training in a car racing game for 2 h induces changes in the hippocampus and parahippocampal gyri. However, the effect of short-term training on the white matter microstructure is unknown. Here we investigated the influence of short learning tasks on structural plasticity in the white matter, and specifically in the fornix, in humans and rats. Human subjects performed a 2 h spatial learning task, and rats underwent training for 1 d in a Morris water maze. Between tasks, subjects were scanned with DTI, a diffusion MRI framework sensitive to tissue microstructure. Using tract-based spatial statistics, we found changes in diffusivity indices in both humans and rats. In both species, changes in diffusion in the fornix were correlated with diffusion changes in the hippocampus, as well as with behavioral measures of improvement in the learning tasks. These results, which provide the first indication of short-term white matter plasticity in the human brain, suggest that the adult brain white matter preserves dynamic characteristics and can be modified by short-term learning experiences. The extent of change in white matter was correlated with their extent in gray matter, suggesting that all components of the neural network are capable of rapid remodeling in response to cognitive experiences.

Structural and functional neuroplasticity in human learning of spatial routes

“…The findings also show that we may not yet have reached the lower limit on how much training is necessary to produce such changes, indicating remarkably rapid short-term structural neuroplasticity of the hippocampus. The study provides an important, independent confirmation of the meticulous previous work carried out in a single laboratory (Blumenfeld-Katzir et al, 2011;Sagi et al, 2012;Hofstetter et al, 2013;Tavor et al, 2013). Like the previous work, this study shows that the magnitude of diffusivity changes in hippocampus are significantly related to the behaviorally-measured magnitude of the learning changes.…”

“…These findings of neuroplasticity have been extended to humans and to shorter training episodes in a series of recent papers from the same laboratory (Sagi et al, 2012;Hofstetter et al, 2013;Tavor et al, 2013). Sagi et al trained both rats and humans on a spatial route-learning task for 2 h, comparing diffusion-weighted imaging before and after the training.…”

Rewiring the primary somatosensory cortex in carpal tunnel syndrome with acupuncture

“…gamers (Imfeld et al, 2009;Hanggi et al, 2010;Hofstetter et al, 2013). In our study, improvements in median nerve latency following acupuncture were indeed associated with reduced fractional anisotropy in S1-adjacent white matter.…”

Interindividual Variation in Fornix Microstructure and Macrostructure Is Related to Visual Discrimination Accuracy for Scenes But Not Faces

“…This finding could reflect the greater sensitivity of the fornix MD to experience-dependent changes (Lebel et al, 2008;Hofstetter et al, 2013). Because FA and MD are both affected by multiple axonal properties, including myelination, density, diameter, and configuration, it is not yet possible to attribute differences between our FA/MD findings to a single white-matter subcomponent .…”