Structural and functional neuroplasticity in human learning of spatial routes

- Spatial route learning was related to decreased water diffusion in the left hippocampus and other spatial cognition areas.
- Both learning and diffusion changes were associated with functional connectivity increases involving the left hippocampus.
- These structural and functional changes occurred within 45 min and were not found in a sensory-motor learning control.
- Both changes could result from alterations of synapses or astrocytes, and reflect spatial learning mechanisms.

Recent findings with both animals and humans suggest that decreases in microscopic movements of water in the hippocampus reflect short-term neuroplasticity resulting from learning. Here we examine whether such neuroplastic structural changes concurrently alter the functional connectivity between hippocampus and other regions involved in learning. We collected both diffusion-weighted images and fMRI data before and after humans performed a 45 min spatial route-learning task. Relative to a control group with equal practice time, there was decreased diffusivity in the posterior-dorsal dentate gyrus of the left hippocampus in the route-learning group accompanied by increased synchronization of fMRI-measured BOLD signal between this region and cortical areas, and by changes in behavioral performance. These concurrent changes characterize the multidimensionality of neuroplasticity as it enables human spatial learning.