Monday, November 1, 2010

Write for your brain

Remember the days when writing by hand was more common than typing?

While those days may be gone, the ability to write by hand is indisputably still useful. This is why getting writer's cramp -- an often-painful condition that inhibits one's ability to write -- can be quite an annoyance.

Luckily, there are several forms of intervention that can be effective in alleviating writer's cramp. In a new study published in NeuroImage, Oliver Granert and colleagues examined how a couple of treatments for writer's cramp affect more than just the ability to write -- they were interested in how training the hand to write changes brain structure and function.

The researchers examined 14 patients with writer's cramp who were part of a clinical trial that assessed two forms of treatment. All 14 patients had their affected hand, wrist, and lower arm immobilized with a splint for 4 weeks prior to treatment. Then for 8 weeks, half of the patients trained their cramp-hand with writing movements using a pen attached to the bottom of a finger splint, and the other half trained finger movements using therapeutic putty (I'm not sure if they used Silly Putty, but if they did, I'm upset that I wasn't eligible to be subject).

The researchers took MRI's of the subjects to assess their brain structure at four points in time: week 0 (before treatment), week 4 (after immobilization), week 8 (after 4 weeks of training), and week 12 (after 8 weeks of training). At these four points in time, a functional measure of brain activity was also taken: the area of the brain that controls movement of the writing hand (M1HAND) was stimulated with electromagnetic induction to activate hand muscles, causing movement. The minimum amount of stimulation required to cause movement in the hand was taken as a measure of 'excitability' -- an assessment of how easily the hand can be moved by brain stimulation.

Both forms of training (writing-movements and putty-playing) were equally effective in reducing the symptoms of writer's cramp. After 4 weeks of immobilization, the grey matter of the brain area that controls movement of the hand decreased in volume, but 4 weeks after motor training the volume increased, and 8 weeks after motor training the volume increased even more. The findings from magnetic stimulation of M1HAND paralleled the changes in brain structure, in that the hand was less easily excitable after immobilization, but gradually became more easily excitable after motor training.

 This study is interesting because it essentially examined  the effects of both de-training and training on brain structure. Changes in brain structure reflected what was happening in terms of training; when the hand was immobilized, the brain area controlling hand movement shrank, but when the hand was mobilized with training, the same brain area grew. Most studies that investigate brain plasticity examine the effects of training -- alone -- on structural changes (e.g. measure brain volume; get subjects to exercise or meditate; measure brain volume again). But investigating opposite forms of training and observing opposite effects on brain structure provides more convincing evidence for a causal relationship between behaviour and anatomy.

Furthermore, the positive relationship between brain structural change and excitability of the hand provides evidence that changes in structure were activity-driven.

It was remarkable how fast the brain changed in response to both training and de-training in this study. I think of times in my life during elementary/high school, when I would write every day, but then I would basically stop writing for the whole summer. When I would come back to school in September, writing felt strange, and I didn't have the same effortless control over my pen that I left with at the end of the previous school-year. My comfort with the pen would then gradually increase as I began to write regularly again. It would be unsurprising if, in fact, these changes in writing ability were caused by my ever-changing brain, an anatomical shadow of my experiences.

Reference:
 
Granert O, Peller M, Gaser C, Groppa S, Hallett M, Knutzen A, Deuschl G, Zeuner KE, & Siebner HR (2011). Manual activity shapes structure and function in contralateral human motor hand area. NeuroImage, 54 (1), 32-41 PMID: 20708692

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