Wednesday, December 10, 2008

Alteration of digital representations in somatosensory cortex in focal hand dystonia

Reference
Elbert, T., Candia, V., Altenmueller, E., Rau, H., Rockstroh, B., Pantev, C., & Taub, E. (1998).
Alteration of digital representations in somatosensory cortex in focal hand dystonia.
NeuroReport 16, 3571-3575.

Summary
Based on an experiment conducted at Institute of Experimental Audiology, University of Munster, Germany, this article compares the results of MEG and MRI scans from 3 groups of human subjects (8 musicians with focal dystonia in right hand, 8 non-dystonic musicians, and 9 non-musician controls) after receiving somatosensory stimulation.
In contrast to the representations of the digits (ie. fingers) in non-musician control subjects, there is a reduced distance between the representational zones of the digits in primary somatosensory cortex for the affected hand of dystonic musicians. This constitutes a change that is in the direction of fusion of the digital receptive fields.
Changes in corticomotor representation, assessed by transcranial magnetic stimulation, have also been reported and consist of distortions of the shape of the motor hand area, extension of its lateral borders, and the emergence of almost discrete secondary motor areas.
At the time of the experiment, it was unclear to which extent the distortions of motor map and the alterations in sensory map were related.
Based on the hypothesis that cortical digital fusion may be a factor in the genesis of focal hand dystonia, a treatment of sensory learning process was developed in the same laboratory and proven effective in several dystonic musicians. This treatment combined extensive practice in making discrete individuated finger movements with methods employed in constraint-induced (CI) movement therapy, an effective new intervention for rehabilitation of movement after stroke.

Review & Reflection
Continued from a 1996 experiment about neuroplasticity/learning origin of focal dystonia in monkeys, this 1998 experiment displays parallel findings in dystonic human subjects and proves that focal dystonia is mainly induced by excessive repetition of trained and purposeful movements.
If this cortical disorder can both be induced and treated by physical therapy, is there such a way in which musicians can practice without contracting focal dystonia? Can we incorporate strategies into our practice routines to consciously and effectively train for healthy and lifelong playing?
On the other hand, what happened to the treatment mentioned at the end of this article? If it already existed in 1998, has there been any follow-up and further development over the past 10 years to make this therapy accessible to dystonic patients from all over the world? Where can we find more information about treatment and prevention of this disorder?

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