Focal dystonia: advances in brain imaging and understanding of ﬁne motor control … · 2015-01-14 · Focal dystonia: advances in brain imaging and understanding of ﬁne motor

Hand Clin 19 (2003) 523–538

Focal dystonia: advances in brain imaging andunderstanding of fine motor control in musicians

Eckart AltenmullerUniversity for Music and Drama, Hannover Institute for Music Physiology and Musicians’ Medicine,

Hohenzollernstr. 47, Hannover D-30161, Germany

Music performance at a professional level isone of the most demanding tasks for the human

central nervous system. It involves the preciseexecution of fast and, in many instances, extremelycomplex physical movements under continuousauditory feedback. A further aspect of music per-

formance—although not specifically addressed inthis article—concerns the involvement of emo-tional experiences.

Extensive practice is required to develop newskills and carry out these complex tasks. Motorskills can be automated only by countless re-

petitions; aural skills, in contrast, are developedthrough a broad variety of listening experiences.These skills are not represented in isolated brain

areas, but rather depend on the multiple con-nections and interactions established during train-ing within and between the different regions of thebrain. The general ability of the human central

nervous system to adapt to changing environmen-tal conditions and newly imposed tasks during itsentire lifespan is referred to as plasticity; in music,

learning through experience and training isaccompanied by development and changes thattake place not only in the brain’s neuronal net-

works, for example, as a strengthening of neurons’connections, but also occur in its overall grossstructure.

The aim of the present article is to give a short

review of current knowledge about the basicneurophysiology and the brain mechanisms in-volved in the acquisition and maintenance of

manual skills in professional musicians. To un-derstand neural substrates of music performance

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it is first necessary to understand some basicneuroanatomy.

Neuroanatomic and neurophysiologic background

Brain imaging methods

During the last decade, rapid improvements inbrain imaging methods have enabled researchers

to carry out substantial new investigations intothe biologic foundations of music performance.The term ‘‘functional brain imaging’’ covers the

various methods of objectively monitoring neuro-nal activity during music production, musicalreasoning, and motor learning in general. Thesemethods allow documentation of the dynamics of

developing brain circuitry during the acquisitionof new manual skills. They show our brain ‘‘atwork.’’

There are two principal approaches that can beused to assess brain activity. The first of thesetakes advantage of methods such as electroen-

cephalography (EEG) and magnetoencephalogra-phy (MEG) that make it possible to measuredirectly the electrical activity of neurons in thecerebral cortex. The second enables the assess-

ment of brain metabolism, cerebral blood flow,and oxygen consumption of nerve cells. Sucha method allows for indirect analysis of neuronal

activity based on the close links between oxygenconsumption and the firing activities of nervecells. The need for oxygen is reflected in local

increases of blood flow in the nervous tissue,which in turn can be assessed by measuring thelocal concentration of radioactively labeledmarker

substances in blood, such as oxygen or glucose.Although positron emission tomography (PET)

ghts reserved.

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524 E. Altenmuller /Hand Clin 19 (2003) 523–538

uses this kind of data collection, there arecertain disadvantages that arise with the use ofthis method because of the application of low

dosages of radioactivity. Much safer is themethod of functional magnetic resonance imag-ing (fMRI) that uses the magnetic properties ofoxygen in blood cells to calculate oxygen

consumption.The main advantage of EEG and MEG is their

excellent temporal resolution, which enables the

monitoring of rapid processes and changes. Thesemethods also allow communication flows betweendifferent areas of the brain to be analyzed through

the calculation of so-called ‘‘coherence’’ betweenactivated neuronal cell assemblies. In contrast, themain advantage of PET and fMRI is their ex-cellent spatial resolution, which allows particular

tasks to be related to specific brain structures.Nevertheless, the temporal resolutions of PETand fMRI are still poor (ranging from 6 seconds

to 1 minute), meaning that more rapid cognitiveprocesses cannot be tracked. A further factor iscost: MEG, PET, and fMRI rely on extremely

complex and expensive technologies. Only EEG isaffordable enough to be used outside specializedbrain imaging centers [1].

General structure of the brain

The human brain can be subdivided into threeparts: the hindbrain, the midbrain, and theforebrain (Fig. 1). The hindbrain consists of the

medulla, pons, and the cerebellum. The hindbrainand the midbrain together constitute the brainstem, which is phylogenetically (ie, in evolution)

the oldest part of the brain. The brain stem

regulates all vital functions such as breathing,heartbeat, arousal, body temperature, and equi-librium. Furthermore, the brain stem controls

many sensory and motor functions, such as eyemovements and the coordination of visual andauditory reflexes. The cerebellum lies behind thepons and mainly processes body equilibrium and

the accurate timing of movements. It is involvedin the learning of motor skills and is particularlyrelevant to the learning skills required in musical

performance. The midbrain lies above the ponsand contains two structures. The first ofthese—the thalamus—transmits incoming infor-

mation from all sensory systems to the cerebralcortex, and so acts as a gateway to the cortex. Thelatter—the hypothalamus—regulates autonomicand endocrine functions. Finally, the forebrain

consists of the two outer cerebral hemispheres andthree deep-lying structures: the basal ganglia, thehippocampus, and the amygdaloid nucleus. The

last two structures lie at the inner border ofthe temporal lobe and are not shown in Fig. 1.The basal ganglia participate in regulating motor

performance; the hippocampus is involved withaspects of memory storage; and the amygdaloidnucleus coordinates autonomic and endocrine

responses in conjunction with emotional states.All cognitive functions are governed by the

cerebral cortex—the outer part of the brain—which is the most complex organ in the human

body. According to recent estimates, the cerebralcortex consists of approximately 100 billionneurons that are interconnected by a dense web

of nerve fibers. By way of synapses, each nerve cellcan communicate with approximately 10,000

Fig. 1. Overview of the anatomic structures of the brain. Left hemisphere is shown.

525E. Altenmuller /Hand Clin 19 (2003) 523–538

other cells. The cerebral cortex is divided into twohemispheres that are interconnected by a largefiber bundle containing approximately 100 millionfibers, known as the corpus callosum.

Four important features characterize the orga-nization of the cortex. First of all, each hemi-sphere is concerned primarily with sensory and

motor processes on the contralateral side of thebody. Second, although seeming to be similar,these hemispheres are neither completely symmet-

ric in structure nor equivalent in function. Third,the cortex is organized hierarchically, with distinctprimary, secondary, and tertiary (or associative)

sensory or motor regions. Primary sensory regions(or areas) are linked directly to the sensory organsby way of the thalamus. Primary motor regionsare linked directly to the spinal chord. Secondary

and tertiary sensory and motor areas are adjacentto the primary areas and process more complexstimulus features. Finally, early intense training

processes starting before the age of approximately10 years may lead to enlargement of the corticalareas involved in the trained faculty.

Each hemisphere is divided into four anatom-ically distinct cortical lobes, called the frontal(front), temporal (side), parietal (upper back), and

occipital (back) lobe (Figs. 1, 2). The frontal lobesare concerned largely with the planning of futureaction and the control of movement. The parietallobes, which are located behind the frontal lobe

and are separated by a deep fissure known as thecentral sulcus, are concerned mainly with the pro-

cessing of somatic sensation and body image. Theoccipital lobes, which are responsible for process-ing vision, lie behind the parietal lobes at the backof the brain. The temporal lobes are separated

from the frontal and the parietal lobes by a furtherdeep fissure, the lateral sulcus. It is these temporallobes that deal not only with hearing, but also

with other aspects, such as cross-modal learning,memory, and emotion.

Neurophysiology of music performance

Music performance on a professional levelrequires extremely refined motor skills that areacquired over many years of extensive training,

and that have to be stored and maintainedthrough further regular practice. Auditory feed-back is needed to improve and perfect perfor-

mance. Music making, therefore, relies primarilyon a highly developed auditory–motor integrationcapacity that can be compared with the oral–aural

loop in speech production. In addition, somato-sensory feedback constitutes another basis ofhigh-level performance. Here, the kinestheticsense, which allows for control and feedback of

muscle and tendon–tension and joint positionsand which enables continuous monitoring offinger-, hand-, or lip-position in the frames of

body and instrument coordinates (eg, the key-board, the mouthpiece), is especially important. Ina more general context, the motor system of music

Fig. 2. Brain regions involved in sensory and motor music processing. Left hemisphere is shown in the foreground, right

in the background. a, area.


performance can be understood as a subspecialtyof the motor systems for planned and skilledvoluntary limb movements.

Voluntary skilled hand movements involvefour cortical regions in both hemispheres (Fig. 2):the primary motor area (M1) located in theprecentral gyrus directly in front of the central

sulcus; the supplementary motor area (SMA)located anterior to the M1 of the frontal lobe andthe inner (medial) side of the cortex; the cingulate

motor area (CMA) below the SMA and above thecorpus callosum on the inner (medial) side of thehemisphere; and the premotor area (PMA), which

is located adjacent to the lateral aspect of theprimarymotor area. SMA,CMA, and PMAcan bedescribed as secondary motor areas, processingmovement patterns rather than simple movements.

In addition to the cortical regions, themotor systemincludes the subcortical structures of the basalganglia and the cerebellum. The sensory areas are

necessary to maintain the control of movements.Their steady kinesthetic feedback information isrequired for any guided motor action. The sensory

areas are located in the primary somatosensoryarea (S1), behind the central sulcus in the parietallobe. The parietal lobe is involved in many aspects

of movement processing. It is an area in whichinformation from multiple sensory regions con-verges. In the posterior parietal area, the bodycoordinates in space are monitored and calculated

and visual information is transferred into bodycoordinates. As far asmusicians are concerned, thisarea is activated prominently during sight-reading

and the playing of a complex piece of music [2].The primary motor area (M1) represents the

movements of body parts in a separate but

systematic order. The representation of the legis located on the top and the inner side of thehemisphere, the arm in the upper portion, and thehand and mouth in the lower portion of M1. This

representation of distinct body parts in corre-sponding brain regions is called somatotopic orhomuncular order. Just as the motor homunculus

is represented upside down, so too is the sensoryhomunculus on the other side of the centralsulcus. The proportions of the motor and the

sensory homunculus are distorted markedly be-cause they are determined by the density of motorand sensory innervation of the respective body

parts. For example, control of fine movementsof the tongue requires many more nerve fiberstransmitting the information to this muscle ascompared with muscles of the back. The hands

therefore require almost one third of the neurons

in this area. The representation of the body partsmay be modified by use, however. Moreover, theprimary motor area does not simply represent

individual muscles: multiple muscular representa-tions are arranged in a complex way so as to allowthe execution of simple types of movements ratherthan the activation of a specific muscle. This is

a consequence of the fact a two-dimensional arrayof neurons in M1 has to code for three-di-mensional movements in space [3,4]. Quite simply,

our brain does not represent muscles, but rathermovements.

The supplementary motor area (SMA) is

involved mainly in the coordination of the twohands, in the sequencing of complex movements,and in the triggering of movements based oninternal cues. It is engaged particularly when the

execution of a sequential movement depends oninternally stored and memorized information. TheSMA can be subdivided into two distinct func-

tional areas. In the anterior SMA, it would seemthat the planning of complex movement patternsis processed. The posterior SMA seems to be

engaged predominantly in two-handed move-ments and, in particular, in the synchronizationof both hands during complex movement pat-

terns. Electrical stimulation of this area duringopen brain surgery can produce an interruption oftwo-handed piano playing [5].

The functionof the cingulatemotor area (CMA)

is still under debate. Electrical stimulation andbrain imaging studies demonstrate its involvementin movement selection based on reward, with

reference to the close links between the cingulategyrus and the emotion-processing limbic system. Insummary, it would seem that the CMA plays

an important role in mediating cortical cognitivefunctions and limbic–emotional functions.

The premotor area (PMA) is engaged primar-ily when externally stimulated behavior is being

planned and prepared. It is involved in the learn-ing, execution, and recognition of limb move-ments and seems to be particularly concerned with

the visual information necessary for movementplanning.

The basal ganglia, located deep inside the

cerebral hemispheres, are interconnected recipro-cally by way of the thalamus to the motor andsensory cortices, thus constituting a loop of in-

formation flow between the cortex and the basalganglia. They are indispensable for any kind ofvoluntary actions that are not highly automated.Their special role consists in the control of

voluntary action by selecting appropriate motor


Fig. 3. Structural changes in the brains of musicians. Some of the brain areas that have been found to be enlarged in

musicians in morphometric studies based on structural magnetic resonance imaging. Arrows indicate primary motor

cortex; planum temporale in the temporal lobe and the anterior part of the corpus callosum.

actions and by comparing the goal and course of

those actions with previous experience. In thebasal ganglia, the flow of information between thecortex and the limbic emotion system, in partic-

ular the amygdala, converges. It is assumed,therefore, that the basal ganglia process andcontrol the emotional evaluation of motor behav-

ior in expected reward or punishment. Finally, thecerebellum contributes essentially to the timingand accuracy of fine-tuned movements.

Musicians’ brains are different

The organization of motor systems describedpreviously can be applied to skilled movements ingeneral. In the following section, however, the

author expands this notion to include literaturethat focuses on the unique qualities of themusicians’ brain.

Amunts and colleagues [6] have estimated the

size of the primary hand motor area by deter-mining the intrasulcular length of the posteriorbank of the precentral gyrus in linearly normal-

ized MRI images. Musicians had a greater intra-sulcular length on both sides, but more so on theright, nondominant hemisphere, resulting in re-

duced asymmetry scores for this area in musi-cians. There was a strong negative correlation

between the time at which musical training had

begun and the size of the right and left handmotor areas. This was reflected behaviorally inreduced hand skill asymmetry and a negative

correlation between hand skill asymmetry and ageof commencement of musical training [7] (Fig. 3).

Many musical instruments require precise co-

ordination of bimanual movements. Musicianswho had begun their musical training before theage of 7 years have a larger anterior midsagittalcorpus callosum (CC) than control subjects or

musicians who started training later [8]. Becausethe size of the midsagittal CC is a good indicatorof the number of axons crossing through the

midline, this finding suggests that this subgroup ofmusicians have enhanced interaction between thetwo hemispheres. Because this part of the corpus

callosum contains fibers from the motor andsupplementary motor areas, it seems plausible toassume that the high demands on coordination

between the two hands and the rapid exchange ofinformation may either stimulate the nerve fibergrowth, the myelination of nerve fibers thatdetermines the velocity of nerve conduction, or

prevent the physiologic loss of nerve tissue dur-ing aging. This hypothesis has been corroboratedby a bilateral transcranial magnetic stimulation

study in pianists and guitarists [9] that revealed


decreased interhemispheric inhibition. This inturn might facilitate bimanual coordination inmusicians by increasing signal transfer between

the hemispheres.Precise timing of movements also requires the

participation of the cerebellum. Recently, malemusicians have been shown to have a greater

mean relative cerebellar volume than male non-musicians. The difference could not be ascribed toa difference in total brain volume, as this was

similar in both groups [10]. Together the findingssuggest that musicians show anatomic differencesin multiple brain areas that are involved in motor

processing. Changes in such large-scale neuralnetworks can be detected using voxel-basedmorphometry, a statistical method of revealingdifferences in brain anatomy between groups

without the need to focus on target structures.Such an analysis revealed increased gray mattervolume in a motor network that included the left

and right primary sensorimotor regions, the leftbasal ganglia, the bilateral cerebellum, and theleft posterior perisylvian region [11].

It is not only motor areas that are subjectto anatomic adaptation, however. By means ofmagnetoencephalography (MEG), the number of

nerve cells involved in the processing of sensorystimulation in individual fingers can be moni-tored. Using this technique, professional violinistshave been shown to possess enlarged sensory

areas corresponding to the index through to thesmall (second to fifth) fingers of the left hand [48].Their left thumb representation (the left thumb

only supports the violin) is no different from thatof nonmusicians. Again, these effects were mostpronounced in violinists who started their in-

strumental training before the age of 10 years.In summary, available evidence suggests that

the central nervous system adapts to the challeng-ing demands of professional musicianship during

prolonged training. These adaptations are un-derstood as brain plasticity. When training startsat an early age (before approximately 7 years),

this adaptation affects brain anatomy in the en-largement of certain brain structures involved inthe respective skill. When training starts later, it

modifies brain organization by rewiring neuronalwebs and involving adjacent nerve cells to con-tribute to the required tasks. These changes

result in enlarged cortical representations of, forexample, specific fingers within existing brainstructures [13].

To understand these processes more fully, the

following section focuses on the short- and long-

term effects of musical training on neuronalrepresentations and brain networks.

Sensorimotor plasticity and sensorimotor learning

Our knowledge concerning the regions andmechanisms of the brain involved in sensorimotorlearning is still incomplete. According to present

concepts, all structures involved in motor controlparticipate in the acquisition of new sensorimotorskills. Besides the motor areas in the cerebralcortex, the basal ganglia and the cerebellum also

play an important role. It has been assumed sincethe nineteenth century that the cerebellum playsan important role in the acquisition of new motor

skills. Such information was based on studiesin which patients suffering from lesions of thecerebellum were found to be unable to increase

the speed of a sequence of complex finger move-ments after practice. More recent evidence dem-onstrates that the cerebellum is involved in the

selection, the sequence, and the timing of move-ments. It seems not to contribute to the motorlearning itself, however, but is engaged primarilyin the modification of performance subsequent to

a learning process [14].Another functional system that is equally

important for the development and learning

of fine finger movements is the basal ganglia.Patients suffering from Parkinson disease havedeficits in learning new motor tasks and, although

they can improve the speed of complex movementpatterns during practice sessions, they do notlearn as quickly and do not reach the level ofperformance of normal control subjects [15].

It has been known for a long time that withincreasing complexity of finger movement sequen-ces, the activity in the SMA and in the premotor

area are enhanced [16]. Using fMRI, Karni andcoworkers [17] investigated the learning of com-plex finger sequences similar to those necessary

for piano playing. After 30 minutes of practice,the representation of the fingers in the primarymotor cortex was increased. Without further

training, however, this effect diminished after 1week with the hand representation returning to itsprevious size. In contrast, continuous practiceresulted in a stable enlargement of the hand area

in primary motor cortex. This effect was specificfor the daily trained sequence of complex fingermovements and did not occur when the subjects

improvised complex finger movements that werenot repeated subsequently. Parallel to the enlarge-ment of the hand area in the primary motor


cortex, the size of the cerebellar hand representa-tion diminished, suggesting that the cerebellumplays no major role in long-term motor learning.It has been proposed on the basis of these

neuroimaging studies that motor learning occursin several phases: a fast initial phase of perfor-mance gains is followed by a period of consolida-

tion that lasts for several hours. This is succeededby a slow learning phase that occurs duringcontinued practice and leads to gradual increases

in performance [18]. When highly skilled pianistsand nonmusicians were exposed to a novel tap-ping task during a single scanning session,

musicians showed a rapid increase of primarymotor cortex activation, whereas nonmusiciansdid not. This effect of recruitment in the primarymotor area thus resembled the slow learning

described previously in nonmusicians, eventhough it occurred within minutes rather thanmonths. It was interpreted therefore as an effect

of pre-practice experience [19]. With regard tosecondary motor areas, in contrast, musiciansshowed a much smaller area of activation in the

SMA, pre-SMA, and CMA in several studies.This finding is compatible with the idea thatthe anterior SMA is essential for setting up and

executing complex motor programs before auto-matic performance. The pianists were able tolearn rapidly and thoroughly the complex fingersequence, reaching a high degree of automaticity

during the first minutes of motor learning.Most interestingly, the motor cortex of the

untrained hand was, at the same time, contribut-

ing to motor learning. This resulted in improvedperformance of the motor task in the untrainedleft hand in pianists and nonmusicians. One of the

most fascinating features of the human sensori-motor system relates to this phenomenon. Despiteclear somatotopic organization of the motorcortex, a movement can be learned with one ex-

tremity and performed with the other. Rijntjesand colleagues [20] investigated subjects writingtheir signature with their right index finger and

with their right big toe. The results of their fMRIstudy show that the movement parameters forthese highly trained movements are stored in

premotor and supplementary motor cortex adja-cent to the right hand area in the primary motorcortex, but are also accessible for the foot area.

Thus, somatotopy in secondary motor areas(SMA, PM) seems to be defined functionally, asabstract movement information independent fromthe executing limb (movement ideas or Bewe-

gungs-Ideen), and not on the basis of anatomic

representations. Although these studies refer toexplicit motor learning by trial and error andsensory feedback, implicit motor learning seemsto be processed in a different way. When subjects

were unaware of a motor learning task—becausetheir attention was drawn to a different prob-lem—activity of the basal ganglia correlated with

motor learning.All of the studies mentioned do not take into

account the special quality of musicianship, and in

particular, the strong coupling of sensorimotorand auditory processing. Practicing an instrumentmeans assembling, storing, and constantly im-

proving complex sensorimotor programs throughprolonged and repeated execution of motor pat-terns under control of the auditory system.

Many professional pianists report that their

fingers move more or less automatically when theyare listening to piano music played by a colleague.In a cross-sectional experiment, the author

demonstrated that, as a result of many yearsof practice, a strong linkage between auditoryand sensorimotor cortical regions develops [21]

(Fig. 4).Furthermore, in a longitudinal study, it was

possible to follow up the formation of such

neuronal multisensory connections together withpiano training in beginner piano players. Non-musicians who had never played an instrumentbefore were trained on a computer piano twice

a week over a period of 5 weeks. They listenedto short piano melodies of a 3-second durationplayed in a five-tone range. After a brief pause

they were required to replay the melodies with theright hand as accurately as possible. After 10minutes of training, listening to piano tunes

produced additional activity in the central andleft sensorimotor regions. In turn, playing ona keyboard produced additional activity in theauditory regions of both temporal lobes. These

early signs of cortical plasticity during the firsttraining session were not stable, but stabilizedwithin the subsequent 5 weeks of training. In the

movement task, the most remarkable effect after 5weeks was the development of additional activa-tion of the right anterior temporal and frontal

lobe. Because it has been demonstrated that thisarea is involved in the perception of pitchsequences, such activation might reflect the

auditory imagery of sounds while moving thefingers on a soundless keyboard. In this context, itshould be mentioned that the results of theexperiment support the idea of the direct effec-

tiveness of mental training on subtle sensorimotor


Fig. 4. Auditory–sensory-motor corepresentation in a professional pianist investigated with fMRI. Listening to piano

tunes activates sensory-motor areas in addition to auditory brain regions; playing on a mute keyboard also activates

mainly left auditory areas. (Courtesy of Dr. Marc Bangert and Dr. Thomas Peschel.)

activation patterns represented in the centralnervous system.

Many questions concerning the brain mecha-nisms of sensorimotor learning and processing

during music performance remain to be clarified. Itis still unclear, for example, how and where therapid adjustment of the sensorimotor system to

different spatial coordinates is processed whenmusicians switch between instruments of differentsizes (eg, from alto flute to piccolo). This phenom-

enon is referred to as response size or movementschema. Besides the limb-independent storage ofmovement information in the secondary motor

areas mentioned previously, the cerebellum mightcalculate a magnification or diminution factor.Another unsolved problem is the neuronal basis ofthe transition from guided slow movements, which

are performedunder steady sensory control, to fast,ballistic movements, which have to be performedwithout online sensory feedback. It is assumed that

different brain regions produce these two types ofmovements and that the transition fromone type tothe other may be incomplete. This might explain

why practicing guidedmovements while slowly andsystematically increasing the tempo may finallyhamper the execution of this movement at a very

fast tempo.

Musicians’ dystonia: loss of manual coordination

in highly trained musicians

There is a dark side to the increasing special-ization and prolonged training of modern musi-

cians, namely loss of control and degradation ofskilled hand movements, a disorder referred to asmusicians’ cramp or focal dystonia. The firsthistorical record from 1830 appears in the diaries

of the famous pianist and composer RobertSchumann [22]. As was probably the case forSchumann, prolonged practice and pain syn-

dromes caused by overuse can precipitate dysto-nia, which is developed by approximately 1% ofprofessional musicians and usually ends their

career [23–25].Focal dystonia is characterized by insidious

or sudden deterioration of voluntary control of

extensively trained, complex sensorimotor skills.Subtle loss of control in fast passages, fingercurling (Fig. 5), lack of precision in forked finger-ings in woodwind players, irregularity of trills,

sticking fingers on the keys, involuntary flexion ofthe bowing thumb in strings, and impairment ofcontrol of the embouchure in woodwind and brass

players in certain registers are the various symp-toms that can mark the beginning of the disorder.At this stage, most musicians believe that the

reduced precision of their movements is causedby a technical problem. As a consequence, theyintensify their efforts, but this often only exacer-

bates the problem [26,27].Males (83%), classical musicians of a younger

age (89%), and instrumentalists such as guitarists,pianists, and woodwinds (together 70%) are

among the most commonly affected by focaldystonia [25,28]. Most patients have solo


Fig. 5. Typical example of musician’s cramp in a pianist, a flutist, and a violinist.

positions and often have a perfectionist, control-type personality. Some statistics concerning pos-sible risk factors are shown in Table 1.

In summary, the development of hand dystoniain musicians is related to the intense and prolongedpractice of fast and highly precise externally

predefined actions. Movement patterns, which areworked on extensively and which require force andskills in one hand at the same time, seem to be

affected predominantly. Chronic pain syndromesand sensory dysesthesia may precede overt dys-tonic symptoms or even may induce the develop-ment of focal dystonia in musicians susceptible to

this movement disorder. Freedom of interpreta-tion in mainly improvising musicians and freedomfrom external professional pressures in amateurs

seems to be a protective factor.

Some remarkable symptoms in focal

hand dystonia

At first glance, some characteristics of focalhand dystonia seem to be incompatible with theview of an organic disorder of the central

sensorimotor system. One of these strange phe-nomena is the task specificity of the motor prob-lem. In most cases, focal dystonia only presents

in the context of instrumental playing. It mightoccur when playing the clarinet, but not whenplaying the saxophone in the same person.

Another interesting feature is the ‘‘sensory-trickphenomenon’’: usually, the coordination problem

largely depends on the afferent somatosensoryinput, for example, from the skin of the fingertips.The author has seen two pianists who had focal

dystonia almost exclusively when playing on ivorybut not on plastic keys. Playing with a latex gloveusually improves the condition. Frequently this

effect is not stable, however, and fades away aftersome minutes of playing.

Focal dystonia often occurs together with focal

tremor as an associated symptom.When observingthe dystonic movement, increased tremor ampli-tude (when compared with the unaffected move-ment of the other hand) can be recognized in more

than 50% of cases. In a few cases, dystonic tremorcan be observed as an isolated but equally disablingsymptom. According to Kaji et al [29], isolated

focal tremor can be interpreted as a ‘‘minus’’variant of focal cramping, characterized as a lackof activation of appropriate muscles in contrast to

the overshooting activation in focal dystonia.Usually neurologic examination does not

reveal any further abnormalities. Additional neu-

rophysiologic and neuroradiologic routine inves-tigations are normal and therefore not helpful inclassifying the focal dystonia with respect to theunderlying pathology.

Focal limb dystonia in musicians may originate

from maladaptive plasticity

Although the neurobiologic origins of this

disorder are not clarified completely, the link


Table 1

Which musician is at risk to develop focal dystonia?

Males 83%

Classical musicians 89%

Younger age

Onset of disorder before age 40 years (average: 32 years, range 15–67 years) 80%

Certain instruments vs. normal distribution

Guitarists 20% 5%

Pianists 29% 15%

Woodwinds (hand dystonia) 21% 16%

Strings 15% 44%

Brass (embouchure d.) 11% 14%

Woodwinds (embouchure d.) 3% 16%

Miscellaneous 2%

n.b. only one double-bass player

Outstanding professional position

Soloists 49%

Solo performing teachers 17%

Tuttists 13%

Students 14%

Amateurs 7%

Personality

Music loving, ambitious, perfectionist, control type

Genetics

(Family history of dystonia) 10%

n ¼ 189 patients, 10/1994–12/1999.

between chronic pain and overuse suggests that

focal dystonia as a cortical sensorimotor mis-learning syndrome may be caused by abnormalplasticity [30]. A study with trained monkeys [31]

demonstrated that chronic overuse and repetitivestrain injury in highly stereotyped movements candegrade actively the cortical representation of the

somatosensory information that guides the finemotor hand movements in primates. A similardegradation of sensory feedback information and

concurrent fusion of the digital representations inthe somatosensory cortex was confirmed in anMEG study conducted in musicians with focaldystonia, although these musicians had no history

of chronic pain (Fig. 6) [12]. These findings arecorroborated by psychophysical measurementsand fMRI investigations in a related disorder,

writer’s cramp, which showed decreased temporaland spatial discrimination at the fingertips [32,33].In a further study, symptoms were provoked in

five dystonic guitarists when they played a modi-fied guitar inside an fMRI scanner [34]. Relativeto nondystonic guitarists, they showed moreactivation of the contralateral sensorimotor cor-

tex but less activation of premotor areas, suggest-ing abnormal recruitment of cortical areasinvolved in the control of complex movements.

Because most musicians play their whole lives

without any coordination problems, however,additional factors, such as a genetic predispositionand a certain susceptibility, seem to play an

important role in the development of focaldystonia.

The most important and, up to now, unsolved

question concerning the therapy of musicians’dystonia is why this condition cannot be over-come easily by retraining and establishing

new and appropriately functioning sensorimotormovement patterns. The author suggests that thisis because of the strong linkage of musicians’movements to emotions and to the limbic system.

From animal experiments it is known that thelimbic system strongly influences memory pro-cesses. Whenever an experience is perceived as a

threatening event, the limbic evaluation systemreinforces memory storage for this experience.When considering musicianship in this context, it

is clear that musicians have to perform complexmovement patterns requiring high-speed motorcontrol under an unyielding auditory feedback. Amusician wants to express and to communicate

his feelings on one side and might be afraid tomake mistakes on the other side. This ‘‘doublelinkage’’ to emotions is reflected in the strong


Fig. 6. Fusion of the somatosensory representation of single digits of the hand in a musician suffering from focal

dystonia. The best-fitting dipoles to explain the evoked magnetic fields after sensory stimulation of single digits (D1–D5)

are shown projected on the individual’s MRI scan. Although for the nonaffected hand the typical homuncular

organization (inset) reveals a distance of �2.5 cm between the sources for the thumb and the little finger (bright circle

and square on the right of the brain), the somatosensory representations of the fingers on the dystonic side are blurred,

resulting from a fusion of the neural networks that process incoming sensory stimuli from different fingers (dark circles).

(Modified from Elbert T, Candia V, Altenmuller E, Rau H, Sterr A, Rockstroh B, et al. Alterations of digital

representations in somatosensory cortex in focal hand dystonia. Neuroreport 1998;9:3571–5, Lippincott, Williams and

Wilkins; with permission).

reward–punishment system acting in professional

musicianship. One could speculate that the fear offalse notes and false movements may enhanceparadoxically the memory for such unsuccess-

ful movements. Support for this theory is theobservation that especially ambitious and enthu-siastic musicians are affected with the disorder

and that a high percentage of dystonic musiciansare suffering from other forms of phobias andpanic attacks [35]. The basal ganglia constitute thecrossover points between the limbic system and

the sensorimotor circuits, and therefore could play

a crucial role concerning the pathophysiologic

mechanisms in dystonia.In a smaller group of musicians there is a close

relationship between musician’s cramp and other

dystonias. In the authors’ group, writer’s crampand musician’s cramp is associated in 37 patients.Writer’s cramp can appear before, synchronously

with, or even years after focal dystonia duringinstrumental playing had become apparent. Inrare cases, focal dystonia manifests as the initialsymptom of a segmental dystonia or a generalized

dystonia. These disorders progress slowly and


include step-by-step larger groups of muscles. Theunderlying pathology is located in the basalganglia [36].

Finally, there is a small subgroup of patientssuffering from focal dystonia caused by a psycho-genic origin. These patients develop incoordina-tion in the context of a neurosis. It is difficult to

distinguish a psychogenic incoordination froma nonpsychogenic one. The author has the im-pression that the pattern of psychogenic incoor-

dination has a more demonstrative character withsometimes strange and ‘‘expressive’’ motions.There are no data available on the long-term

outcome in these patients. The author supposesthat the spontaneous remission of focal dystoniaseen occasionally might occur predominantly inthese patients.

Treatment of musicians’ dystonia

The different origins of focal dystonia requiredifferent therapeutic approaches. In Fig. 7, a

simplified diagram of the author’s understandingof the pathologic mechanisms in focal dys-tonia is shown. As a hypothesis, the author sug-

gests that inappropriate sensorimotor programshave been established because of misguided plas-ticity of cortical or subcortical sensorimotor re-presentations of the affected limbs. Because large

neural circuits connect premotor, motor andsensory areas, the basal ganglia, and the limbicsystem, the origin of the fatal maladaptive process

may be in one of these structures, but it influencesthe whole circuit (Fig. 7).

The aim of treatment must be establishing

a new sensorimotor program. This can be ac-hieved using different methods. One possibility iscircumventing the disabled movements by mod-

ifications of the instrument (eg, alteration of theposition of keys in woodwinds and use of otherergonomic devices). Neuromuscular reeducation(eg, Feldenkrais and Alexander techniques) may

be helpful, although in the author’s experience,functional recovery to a high technical standard isan exception. Retraining by experienced teachers

as offered in Europe by Phillip Chamagne [37] andLaurent Boullet [38] seems to be more effective;however, these methods usually require several

years of specific instruction.A novel treatment approach is based on the

principle of the constraint-induced movementtherapy (CIMT) in stroke patients. CIMT in

stroke patients means that patients are encour-

aged and even forced to use the paretic limbs andthat movements of the unaffected healthy limbsare actively constrained (eg, by fixing them in

a cast). Stroke patients treated in such a way hadbetter outcome with respect to their motorabilities. In brain imaging studies in these patients,it emerged that the cortical representation of the

affected limbs was reorganized better than inuntreated controls. For dystonic musicians, thisbehavioral treatment has been adapted by a group

in Konstanz in close cooperation with theauthor’s institution [39,40]. In musicians sufferingfrom hand dystonia, the disturbed movement

patterns usually include one focal dystonic fingercramping in flexion and compensating fingerstrying to help the flexed finger out of its position.During the behavioral therapy, the compensating

finger is immobilized with a splint. Under theseconditions the dystonic finger has to carry outrepetitive exercises in coordination with one or

more of the nonsplinted fingers according toa certain schedule. As a result, six pianists andtwo guitarists showed marked improvement of the

dystonia, whereas woodwinds did not benefitfrom this therapy. At present, follow-up studiesconcerning long-term improvement under this

therapy are conducted. Furthermore, the authorplans to apply this therapy in a considerablylarger group of dystonic musicians. Related to thetreatment mentioned previously and similarly

based on the assumption of cortical dysplasticityin focal dystonia, a prospective treatment trial ona mixed group of patients with focal dystonia was

conducted [41]. The investigators used variousmethods of sensory retraining and visual mirrorfeedback in addition to physiotherapy for

strengthening the hand muscles. The patientsimproved significantly in obtaining motor control,accuracy, sensory discrimination, and physicalperformance. Prolonged splinting and careful

retraining yielded equal improvements in a groupof Italian musicians [42].

Another therapeutic option is a symptomatic

treatment with local intramuscular injections ofbotulinum toxin (Botox). Botulinum toxins areproduced by Clostridium botulinum bacteria; seven

serotypes or forms of botulinum toxin have beenisolated (A–G). Each has different properties andactions and no two are exactly alike. Of these

subtypes, botulinum toxin type A and B arecurrently the most studied and most widely used.Intramuscularly injected, Botox reduces the re-lease of the neurotransmitter acetylcholine at the

neuromuscular junction, resulting in a weakening


Fig. 7. Simplified scheme of the different methods of treatment in focal dystonia related to the underlying

pathophysiologic mechanisms. For further explanations see text.

of the muscle [43]. The effect of Botox lasts forapproximately 2–3 months and is reversible.

Botox has been used with some success inmusicians with focal dystonia. Its therapeuticwindow is narrow, however, rendering its man-

agement difficult. There is a fine line betweenadministering not enough Botox and too much ofit, which may weaken the muscles and impair their

control [24,44–46]. Injections into the intrinsichand muscles hold several advantages overinjections into the long flexor and extensormuscles of the forearm. There is a lower risk for

impairing movement in adjacent fingers, eitherbecause of diffusion of the botulinum toxinsolution or the intermingling of muscular fascicles

of different fingers. The required dosage is small,which lowers the risk for antibody development.In the case of overdosage, serious paresis impair-

ing the function of dystonic fingers is less frequentand is compensated for more easily by thefunctionally intact long flexors and extensors.

Injections should be performed, however, onlyinto those intrinsics that are not required toperform rapid lateral movements of the fingerson the instrument. In woodwinds, most of the

instruments equipped with the Boehm-system(eg, flute, saxophone, clarinet) almost exclusively

demand such lateral movements in the right andleft little fingers. According to the author’s

experience, injections into the involved interosseusand lumbrical muscles therefore should be ad-ministered in all cases of flexion or extension

dystonia in index, middle, or ring finger ofwoodwind instrumentalists.

Anticholinergic drugs that influence predomi-

nantly neurotransmission in the basal ganglia arehelpful in some cases of focal dystonia. Accord-ing to the author’s experience, trihexyphenidyl(Artane�) is the most effective substance. It must

be mentioned, however, that long-term improve-ment is not so common, because many patients donot tolerate the drug over a long period of time.

Even at a low dosage of 4–6 mg daily, side effectssuch as fatigue, dry mouth, or slight memoryimpairment are reported frequently. Also used is

Madopar, which acts on the dopaminergic trans-mission; however, it does not seem to be aseffective as Artane [47].

Finally, it is crucial to consider the psychologicfactors when treating patients with focal dystonia.The frustrating dystonia paradox mentioned pre-viously should be an occasion to reflect on one’s

attitudes concerning the playing of an instrumentand the life of a musician. It is important to keep


in mind that musicians play music and do not

‘‘work an instrument.’’ Helping the patient tobreak out of their prison of coordination prob-lems, helping them to widen and free their mind,

and enabling them to develop perspectives for thefuture is important.

What can doctors do for patients with focal

limb-dystonia?

The treatment of focal dystonia remains

a difficult task for the performing artist’s doctor.Improvement in symptoms can be attained inmany cases, but it is understandable that for manypatients this is not enough. They want all or

nothing! Once having played Tchaikovsky’s B flatminor concerto as a soloist with the BerlinPhilharmonic it is not easy to accept limitations

in repertoire or to perform at a lower technicallevel in a small town. How to deal with thisproblem must be part of the psychologic support

and must be considered when developing futureperspectives with the individual patient. As ageneral rule, complete recovery cannot be ac-

hieved. Even under optimal conditions, somerestrictions in repertoire or tempo and power ofcertain movements remain. The results of treat-ment in the author’s group are summarized in

Table 2.The author’s experience indicates the six most

important steps in treating musicians suffering

from focal limb dystonia are:

1. Make the right diagnosis. Approximately40% of the author’s patients came with

Table 2

Outcome of treatment in focal dystonia

No treatment wanted or possible n = 35 (19%)

Botox injections n = 54 (29%)

Long-term improvement n = 20 (11%)

Anticholinergic drugs n = 75 (40%)


Constrained movement therapy n = 11 (6%)

Long-term improvement n = ?

Ergonomic changes eg, keys n = 4 (2%)


No benefit at all from any therapy n = 42 (22%)

Change of profession at present n = 26 (14%)

Positive development

without treatment

n = 14 (7%)

No information about follow-up n = 20 (11%)

Multiple naming possible

n = 189 patients, 10/1994–12/1999.

a wrong diagnosis (eg, tendinitis, snapping-finger syndrome, depression).

2. Relieve your patient of guilt feelings. De-

veloping focal dystonia is not from a faultytechnique or a faulty posture. It is fate and itprobably can happen to any passionatemusician.

3. Protect your patient from useless cures.4. Discuss the therapeutic possibilities realisti-

cally. Do not awaken false hopes.

5. Pragmatic therapy should include Botox,anticholinergic drugs, and, depending oninstrument and individual situation, reeduca-

tion with an experienced instructor.6. Your patient needs steady psychologic sup-

port. Help them to not look back all the time,deploring their misfortune, but to develop

new perspectives.

Acknowledgments

This work was supported by a grant from theDFG (SPP 1001, Al 269/1-3). Many thanks toMarc Bangert, Thomas Elbert, Hans-Christian

Jabusch, Thomas Munte, and Thomas Peschel,who all contributed to the investigations andshared their enthusiasm for the neurophysiology

of the musician’s hand with me.

References

[1] Altenmuller E, Gerloff Ch. Psychophysiology and

the EEG. In: Niedermeyer E, Lopes da Silva F,

editors. Electroencephalography. 4th edition. Balti-

more: Williams and Wilkins; 1998. p. 637–55.

[2] Sergent J. Mapping the musician brain. Hum Brain

Map 1993;1:20–38.

[3] Graziano MS, Taylor CS, Moore T, Cooke DF.

The cortical control of movement revisited. Neuron

2002;36:49–62.

[4] Rouiller EM. Multiple hand representations in the

motor cortical areas. In: Wing AM, Haggard P,

Flanagan JR, editors. Hand and brain. San Diego:

Academic Press; 1997. p. 99–124.

[5] Marsden CD, Deecke L, Freund H-J. The functions

of the supplementary motor area. Summary of

a workshop. In: Luders H, editor. Advances in

neurology. Vol. 70 Supplementary sensorimotor

area, Philadelphia: Lippincott-Raven Publishers;

1996. p. 477–87.

[6] Amunts K, Schlaug G, Jancke L, Steinmetz H,

Schleicher A, Dabringhaus A, Zilles K. Motor

cortex and hand motor skills: structural compliance

in the human brain. Hum Brain Map 1996;5:

206–15.


[7] Jancke L, Schlaug G, Steinmetz H. Hand skill

asymmetry in professional musicians. Brain Cog

1997;34:424–32.

[8] Schlaug G, Jancke L, Huang Y, Steinmetz H.

Increased corpus callosum size in musicians. Neuro-

psychologia 1995;33:1047–55.

[9] Ridding MC, Brouwer B, NordstromMA. Reduced

interhemispheric inhibition in musicians. Exp Brain

Res 2000;133:249–53.

[10] Schlaug G. The brain of musicians. A model for

functional and structural adaptation. Ann NY

Acad Sci 2001;930:281–99.

[11] Sluming V, Barrick T, Howard M, Cezayirli E,

Mayes A, Roberts N. Voxel-based morphometry

reveals increased gray matter density in Broca’s area

in male symphony. Neuroimage 2002;17:1613–22.

[12] Elbert T, Candia V, Altenmuller E, Rau H, Sterr A,

Rockstroh B, et al. Alterations of digital represen-

tations in somatosensory cortex in focal hand

dystonia. Neuroreport 1998;9:3571–5.

[13] Munte TF, Altenmuller E, Jancke L. The musician’s

brain as a model of neuroplasticity. Nat Rev

Neurosci 2002;3:473–8.

[14] Seidler RD, Purushotham A, Kim SG, Ugurbil K,

Willingham D, Ashe J. Cerebellum activation as-

sociated with performance change but not motor

learning. Science 2002;296:2043–6.

[15] Salmon DP, Butters N. Neurobiology of skill and

habit learning. Curr Opin Neurobiol 1995;5:184–90.

[16] Roland P, Larsen B, Lassen NA, Skinhoi E.

Supplementary motor area and other cortical areas

in organization of voluntary movements in man.

J Neurophysiol 1980;43:118–36.

[17] Karni A, Meyer G, Jezzard P, Adams MM, Turner

R, Ungerleider LG. Functional MRI evidence for

adult motor cortex plasticity during motor skill

learning. Nature 1995;377:155–8.

[18] Karni A, Meyer G, Rey-Hipolito C, Jezzard P,

Adams M, Turner R, Ungerleider LG. The ac-

quisition of skilled motor performance: fast and

slow experience-driven changes in primary motor

cortex. Proc Natl Acad Sci USA 1998;95:861–8.

[19] Hundt-Georgiadis M, Cramon DY. Motor-learning

related changes in piano players and non-musicians

revealed by functional magnetic resonance signals.

Exp Brain Res 1999;125:417–25.

[20] Rijntjes M, Dettmers C, Buchel C, Kiebel S,

Frackowiak RS, Weiller C. A blueprint for move-

ment. Functional and anatomical representations

in the human motor system. J Neurosci 1999;19:

8043–8.

[21] Bangert M, Haeusler U, Altenmuller E. On

practice: how the brain connects piano keys and

piano sounds. Ann NY Acad Sci 2001;930:425–8.

[22] Schumann R. Diaries. Quotation according to

Eismann G, Hrsg. Tagebucher. Basel/Frankfurt:

Stroemfeld/Roter Stern; 1971. Band I.

[23] Altenmuller E. Fokale Dystonien bei Musikern:

Eine Herausforderung fur die Musiker-Medizin.

Musikphysiologie und Musikermedizin 1996;3:

29–40.

[24] Altenmuller E. Causes et traitements de la dystonie

de fonction chez les musicians. Une etude sur 5 ans.

Medecine des Arts 2001;36:19–26.

[25] LimVK,Altenmueller E, Bradshaw JL. Focal dysto-

nia: current theories.HumMovSci 2001;20:875–914.

[26] Fry HJ, Hallett M, Mastroianni T, Dang N,

Dambrosia J. Incoordination in pianists with over-

use syndrome. Neurology 1998;51:512–9.

[27] Lederman RJ. Focal dystonia in instrumentalists:

clinical features. Med Prob Perf Art 1991;6:132–6.

[28] Lim VK, Altenmuller E. Musicians’ cramp: in-

strumental and gender differences. Med Prob Perf

Art 2003;18:21–6.

[29] Kaji R, Shibasaki H, Kimura J. Writer’s cramp. A

disorder of a motor subroutine? Ann Neurol

1995;38:835–6.

[30] Hallett M. The neurophysiology of dystonia. Arch

Neurol 1998;55:601–3.

[31] Byl NN, Merzenich MM, Jenkins WM. A primate

genesis model of focal dystonia and repetitive strain

injury. Neurology 1996;47:508–20.

[32] Sanger TD, Tarsy D, Pascual-Leone A. Abnormal-

ities of spatial and temporal sensory discrimination

in writer’s cramp. Mov Disord 2001;16:94–9.

[33] Sanger TD, Pascual-Leone A, Tarsy D, Schlaug G.

Nonlinear sensory cortex response to simultaneous

tactile stimuli in writer’s cramp. Mov Disord

2002;17:105–11.

[34] Pujol J, Roset-Llobet J, Rosines-Cubells D, Deus J,

Narberhaus B, Valls-Sole J, et al. Brain cortical

activation during guitar-induced hand dystonia

studied by functional MRI. Neuroimage 2000;12:

257–67.

[35] Jabusch HC, Muller S, Altenmuller E. Psychologi-

sche Pradispositionen bei Musikern mit Bewegungs-

storungen. Musikphysiologie und Musiker-Medizin

2000;7:126–7.

[36] Sheehy MP, Marsden CD. Writers’ cramp—a focal

dystonia. Brain 1982;105:461–80.

[37] Chamagne P. Traitement des dystonies de fonctions

des musiciens par une reeducation pronlongee.

Revue Medecine des Arts 2001;36:31–3.

[38] Boullet L. Is there a cure for focal dystonia?

[abstract]. Freiburg, Germany: Presented at the Pro-

ceedings of the Deutsche Gesellschaft fur Musik-

physiologie und Musiker-Medizin, April 4, 2003.

[39] Candia V, Elbert T, Altenmuller E, Rau H, Schafer

T, Taub E. A constraint induced movement therapy

for focal hand dystonia in musicians. Lancet

1999;353:42.

[40] Candia V, Schafer T, Taub E, Rau H, Altenmuller

E, Rockstroh B, et al. Sensory motor retuning:

a behavioral treatment for focal hand dystonia of

pianists and guitarists. Arch Phys Med Rehabil

2002;83:1342–8.

[41] Byl NN, McKenzie A. Treatment effectiveness for

patients with a history of repetitive hand use and


focal hand dystonia: a planned, prospective follow-

up study. J Hand Ther 2000;13:289–301.

[42] Priori A, Pesenti A, Cappellari A, Scarlato G,

Barbieri S. Limb immobilization for the treatment

of focal occupational dystonia. Neurology 2001;

57:405–9.

[43] Coffield JA, Considine RV, Simpson LL. The site

and mechanism of action of botulinum neurotoxin.

In: Jankovic J, Hallett M, editors. Therapy with

botulinum toxin 3–13. New York: Marcel Dekker;

1994.

[44] Charness ME, Ross MH, Shefner JM. Ulnar

neuropathy and dystonic flexion of the fourth and

fifth digits: clinical correlation in musicians. Musc

Nerve 1996;19:431–7.

[45] Cole R, Hallett M, Cohen LG. Double-blind trial of

botulinum toxin for treatment of focal hand

dystonia. Mov Disord 1995;10:466–71.

[46] Ross MH, Charness ME, Sudarsky L, Logigian EL.

Treatment of occupational cramp with botulinum

toxin: diffusion of toxin to adjacent noninjected

muscles. Musc Nerve 1997;20:593–8.

[47] Muller F, Dichgans J, Jankovic J. Dyskinesias. In:

Brandt T, Caplan LR, Dichgans J, Diener HC, Ken-

nard C, editors. Neurological disorders: course and

treatment. SanDiego:AcademicPress; 1996. p. 779–95.

[48] Elbert T, Pantev Ch., Wienbruch Chr., Rockstroh

B, Taub E. Increased cortical representation of the

fingers of the left hand in string players. Science

1995;270:305–7.

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