Experience-dependent rapid structural changes in the human brain: A systematic review.

Structural brain plasticity has traditionally been viewed as a gradual process developing over days to weeks of training or experience. Recent neuroimaging evidence, however, demonstrates that measurable structural changes can occur within hours of behavioral or physiological manipulation, a phenomenon referred to as rapid structural plasticity. This systematic review synthesizes evidence for such short-interval (<2 h) structural alterations in gray matter across magnetic resonance imaging (MRI) modalities in humans. Thirty studies met inclusion criteria, assessing diffusion-weighted magnetic resonance imaging (DW-MRI) and T1-weighted MRI (T1W-MRI) measures including voxel-based morphometry (VBM) and cortical thickness (CT). Interventions included motor and spatial learning, perceptual and language training, stress, exercise, and pharmacological manipulations. Across paradigms, DW-MRI studies consistently reported rapid decreases in mean diffusivity within task-relevant regions such as the hippocampus, cerebellum, and primary motor cortex. Similarly, studies using T1W-MRI revealed short-term increases in CT or gray matter volume (GMV), typically within one hour. However, the duration of tasks and timing of imaging varied across studies, complicating direct comparisons. Research combining perfusion-sensitive measures, including arterial spin labeling and functional MRI, further indicated that some apparent GMV changes may reflect transient shifts in cerebral blood flow or extracellular fluid. Together, these findings suggest that rapid, region-specific structural modulations can occur within hours of experience. Future research combining multimodal MRI, dense temporal sampling, and physiological control measures will be essential to disentangle genuine structural plasticity from transient hemodynamic, fluid or metabolic effects, thereby refining the temporal and mechanistic characterization of rapid brain plasticity.