Thursday, April 05, 2012

Our brain structure changes after two hours of learning.

Sagi and colleagues have provided the first evidence that rapid structural plasticity can be detected in humans after just 2 hr of playing a video game. To assess brain structure they used diffusion magnetic resonance imaging, a technique sensitive to the self-diffusion of water molecules that depends on tissue architecture (how freely water diffuses depends on the space between the objects such as neurons, glia, and blood vessels, that it is moving through). They showd that only two hours of learning can cause a mean diffusivity reduction in the human hippocampus. In a similar supporting study on rats, the authors were able to show that changes in brain derived neurotropic growth (BDNF) factor correlated with the structural change measured by MRI. I'm passing on the abstract, and for those of you who like data, one of the figures from their paper.

The timescale of structural remodeling that accompanies functional neuroplasticity is largely unknown. Although structural remodeling of human brain tissue is known to occur following long-term (weeks) acquisition of a new skill, little is known as to what happens structurally when the brain needs to adopt new sequences of procedural rules or memorize a cascade of events within minutes or hours. Using diffusion tensor imaging (DTI), an MRI-based framework, we examined subjects before and after a spatial learning and memory task. Microstructural changes (as reflected by DTI measures) of limbic system structures (hippocampus and parahippocampus) were significant after only 2 hr of training. This observation was also found in a supporting rat study. We conclude that cellular rearrangement of neural tissue can be detected by DTI, and that this modality may allow neuroplasticity to be localized over short timescales.

Figure (Click on figure to enlarge it) - Structural Remodeling of Brain Tissue, Measured by DTI as Changes in MD after 2 hr of Training on a Spatial Learning and Memory TaskThe following statistical analyses were employed: paired t tests between the MD maps before and after the task in the learning group (A and F); planned comparisons analysis of the learning versus control groups with respect to scan time with predicated effect in the learning group only (B and G); and linear effect between groups (C and H) as well as a group by time interaction following ANOVA (D and I). The effects were found in the left hippocampus (A–D) and right parahippocampus (F–I). The parametric maps in these images were generated at a significance level of p less than 0.005 (uncorrected). The enlarged subset in those images indicates the significant voxels following correction for multiple comparisons (p less than 0.05, corrected). In the enlarged subset the corrected p value color scale is between 0.005 and 0.05. L indicates the left side of the brain. (E) and (J) show the MD values in the clusters in the subset of (A) and (F) (mean ± SEM). (K) shows the correlation analysis between subjects' improvement rates (see Figure 1) and decrease in MD in the right parahippocampus (of the cluster in F).


Irma Walter said...

What's a diffusivity reduction, or rather, what does that mean to the brain?

Deric Bownds said...

Diffusivity is just how fast water or other kinds of molecules can move over a distance in the brain around objects like cells and blood veins that block that free movement. So, if diffusivity decreases, that mean, the stuff blocking its movement has become larger.

Phillip Mario said...

Really? Sounds interesting. Thought that changes that may happen to the brain is only due to its overexposure to tiredness and stuff. But if reflexes work for the brain, then it's a great deal to make it work even better. And can I just ask if the decrease of diffusivity also means that a portion of the brain is used more frequently than the other parts?

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