‘There was a question of not having a purpose in life. Just floundering’.
Leon Fleischer was a true musical prodigy. By the age of sixteen he performed with the New York Philharmonic. He was called ‘the pianist find of the century’. Suddenly, in 1964, he lost control over his right hand. His fingers would simply curl up. The end of his career.
The illness which befell Leon Fleischer and about 1% of his fellow musicians is called focal dystonia, the loss of control over muscles involved in a highly trained task. It is a career breaker coming out of the blue. An investigation into the underlying neural problems leads on a journey into the brain’s muscle control circuitry and its ability to learn.
The human brain’s motor system which controls muscle movement is well understood. When one stimulates areas in the precentral sulcus (see Figure on the right) one can observe muscle movements. I actually once saw my own finger move when this area was magnetically stimulated. Because the role of this brain area in muscle control is so well understood, it is simply called the primary motor cortex, or M1 for short.
The organisation within the primary motor cortex is such as described in the Figure in red: inside the brain the leg muscles are controlled, going to the side come hand areas and eventually facial muscles. Localisation of function (where in the brain is x?) doesn’t get much better.
Motor learning is nothing else than changing the brain in order to better perform a task. Roughly, one learns when an intended outcome and sensory feedback about the actual outcome disagree. Focal dystonia is probably an example of how the brain’s ability to learn can be pushed too far. This illness messes up the localisation of function in one of the most clearly organised brain areas.
For example, the primary motor cortex’s finger areas are usually nicely aligned. However, when dystonia affects a finger, its brain area moves away from its allocated place. Furthermore, the amount of brain tissue which only controls the dystonic finger is reduced, likely because adjacent fingers take over some of the finger’s area (Burman et al., 2009). Thus, ineffective control over muscles because of a subtle disorganisation of motor control areas could be the brain basis for focal dystonia.
On the other hand, rather than the outcome of learning – motor control area changes – the process of learning could also be the reason for the illness. Sensory feedback from the fingers arrives on the other side of the ridge that separates the frontal part of the brain (which includes the motor cortex) and the back part beginning with the so called parietal cortex. The area responding to touch is called the somatosensory cortex and – as can be seen in the Figure in blue – it is also very well organised.
Elbert and colleagues (1998) found that dystonic musician’s digit areas were unusually tightly packed. Their MEG study thus shares some of the findings with Burman et al.’s fMRI study. Apparently, movement execution is disorganised, but also feedback is to some degree jumbled up. The brain seems to have lost some of its nice organisation in areas related to dystonic impairments.
Lastly, a recent meta-analysis by Zheng and colleagues (2012) adds two more things to this picture. The aforementioned activation abnormalities in sensorimotor areas are mirrored in unusual structural features. Furthermore, areas deep inside the brain related to motor planning and movement initiation also show such structural abnormalities.
Focal dystonia seems to affect all sorts of parts of the brain’s sensori-motor system both in terms of brain structure and how the structure is used. Which of these effects actually cause the illness and which are just consequences cannot be said based on these findings. Still, the unusual mappings in the motor and the somatosensory cortices together with deep brain abnormalities are an indication that the brains of dystonic musicians may have adapted too much to the demands of professional instrument playing. Neither the brain’s control over the body’s muscles is good enough anymore nor the feedback from the fingers.
There is still no reliable cure for focal dystonia. Some people treat the symptoms with botox to the affected muscles. Otherwise, retraining of the brain’s sensorimotor areas away from the maladaptation is currently being tried.
How did Leon Fleischer deal with focal dystonia? He had to change his involvement with music to one-armed piano pieces, conducting, and music teaching. Later, surgery and some treatment of the symptoms improved his condition. He is by no means cured. Still, he can finally play the piano again with both hands. As you can hear and see in the Academy Award nominated documentary Two Hands, his performance sounds wonderful, but look closely at his right hand’s fingers.
This is what a breakdown in brain organisation looks like.
Burman, D.D., Lie-Nemeth, T., Brandfonbrener, A.G., Parisi, T., & Meyer, J.R. (2009). Altered Finger Representations in Sensorimotor Cortex of Musicians with Focal Dystonia: Precentral Cortex Brain Imaging and Behavior, 3, 10-23 DOI: 10.1007/s11682-008-9046-z
Elbert, T., Candia, V., Altenmüller, E., Rau, H., Sterr, A., Rockstroh, B., Pantev, C., & Taub, E. (1998). Alteration of digital representations in somatosensory cortex in focal hand dystonia. Neuroreport, 9 (16), 3571-3575 PMID: 9858362
Zheng, ZZ., Pan, PL., Wang, W., & Shang, HF. (2012). Neural network of primary focal dystonia by an anatomic likelihood estimation meta-analysis of gray matter abnormalities Journal of the Neurological Sciences, 316, 51-55 DOI: 10.1016/j.jns.2012.01.032