bangert, m., & altenmüller, e. o. (2003). mapping perception to action in piano practice- a...

7/27/2019 Bangert, M., & Altenmller, E. O. (2003). Mapping perception to action in piano practice- a longitudinal DC-EEG st

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BMC Neuroscience

Open AccesResearch article

Mapping perception to action in piano practice: a longitudinalDC-EEG study

Marc Bangert*1,2

and Eckart O Altenmller*1

Address: 1Institute of Music Physiology and Musicians Medicine, Hanover University of Music and Drama, Hohenzollernstrasse 47, D-30161Hanover, Germany and 2Dept of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Ave, Boston, MA02215, USA

Email: Marc Bangert* - [email protected]; Eckart O Altenmller* - [email protected]

* Corresponding authors

Abstract

Background: Performing music requires fast auditory and motor processing. Regarding

professional musicians, recent brain imaging studies have demonstrated that auditory stimulation

produces a co-activation of motor areas, whereas silent tapping of musical phrases evokes a co-activation in auditory regions. Whether this is obtained via a specific cerebral relay station is

unclear. Furthermore, the time course of plasticity has not yet been addressed.

Results: Changes in cortical activation patterns (DC-EEG potentials) induced by short (20 minute)

and long term (5 week) piano learning were investigated during auditory and motoric tasks. Twobeginner groups were trained. The 'map' group was allowed to learn the standard piano key-to-

pitch map. For the 'no-map' group, random assignment of keys to tones prevented such a map.

Auditory-sensorimotor EEG co-activity occurred within only 20 minutes. The effect was enhanced

after 5-week training, contributing elements of both perception and action to the mentalrepresentation of the instrument. The 'map' group demonstrated significant additional activity of

right anterior regions.

Conclusion: We conclude that musical training triggers instant plasticity in the cortex, and that

right-hemispheric anterior areas provide an audio-motor interface for the mental representation

of the keyboard.

BackgroundThe mastering of a musical instrument requires some ofthe most sophisticated skills, including fast auditory as

well as motor processing. The performance targets of thehighly trained movement patterns are successions ofacoustic events. Therefore, any self-monitoring duringmusical performance has to rely on quick feedforward orfeedback models that link the audible targets to therespective motor programs. Years of practice may estab-lish a neuronal correlate of this connection, which has

recently been shown by brain imaging studies for bothdirections, auditory-to-motor, and motor-to-auditory.

For auditory-to-motor processing: Professional musi-cians often report that pure listening to a well-trainedpiece of music can involuntarily trigger the respective fin-ger movements. With a magnetoencephalography (MEG)experiment, Haueisen & Knsche [1] could demonstratethat pianists, when listening to well-trained piano music,exhibit involuntary motor activity involving the contralat-eral primary motor cortex (M1).

Published: 15 October 2003

BMC Neuroscience 2003, 4:26

Received: 27 July 2003Accepted: 15 October 2003

This article is available from: http://www.biomedcentral.com/1471-2202/4/26

2003 Bangert and Altenmller; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are per-mitted in all media for any purpose, provided this notice is preserved along with the article's original URL.
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For motor-to-auditory processing as a possible feedfor-ward projection, Scheler et al. [2] collected functionalmagnetic resonance (fMRI) brain scans of eight violinists

with German orchestras and eight amateurs as theysilently tapped out the first 16 bars of Mozart's violin con-

certo in G major. The expert performers had significantactivity in primary auditory regions, which was missing inthe amateurs.

Both directions of co-activation have been investigatedin eight pianists and eight non-pianists in a previouscross-sectional study using DC-EEG [3]. In two physicallydifferent tasks involving only hearing or only motormovements respectively, the non-pianists exhibited dis-tinct cortical activation patterns, whereas the pianistsshowed very similar patterns (based on correlation and

vector similarity measures).

All of these studies have dealt with cross-sectional com-parisons of expert musicians to non-experts. An issue thatcan not be addressed by this approach is to what extentthe demonstrated co-activation processes are a result ofmany years of practice experience of the professionals, orif the time course establishing the phenomenon reveals afaster learning pace, even in the initial stages of practice.

The crucial aspect of this approach is that, in addition tocomparing experts to novices, the effects of practice oncortical activity is monitored in a group of beginners overa period of several weeks.

Using transcranial magnetic stimulation (TMS), Pascual-

Leone et al. [4] demonstrated how plastic changes in thecerebral cortex during the acquisition of new fine motorskills occur within only five days. Subjects who learnedthe one-handed, five-finger exercise through daily 2-hourpiano practice sessions, enlarged their cortical motor areastargeting the long finger flexor and extensor muscles, anddecreased their activation threshold. Furthermore, thestudy provided evidence that the changes were specificallylimited to the cortical representation of the hand used inthe exercise, and that the changes take place regardless

whether the training had been performed physically, ormentally only. Moreover, Classen et al. [5] showed that inmotor skill acquisition the first effects of short-term plas-

ticity appear not only in a matter of days, but even inminutes.

Whereas short-term practice seems to enlarge respectivecortical motor areas, sustained long-lasting continuationof the training can yield a reduction of the size of theseareas. Jncke and co-workers [6] showed that during abimanual tapping task, the primary and secondary motorareas (M1, SMA, pre-SMA, and CMA) were considerablyactivated to a much lesser degree in professional pianiststhan in non-musicians. The results suggest that the long

lasting extensive hand skill training of the pianists leads togreater efficiency which is reflected in a smaller number ofactive neurons needed to perform given fingermovements.

The present investigation deals not only with the plasticityof motor representations but also with the issue of audi-tory-sensorimotor integration in piano practice. Auditoryfeedback is essential for this kind of motor skill acquisi-tion. The use of a computer-controlled digital pianoallows us to access and to isolate the independent targetfeatures (parameters pitch, onset time, and loudness).Special attention is directed to an experimental dissocia-tion of key presses and the associated acoustic events. Theprobe tasks of the paradigm involved only auditory oronly motoric aspects of the original complex audio-motortask during piano practice.

We utilized DC-EEG to clarify the temporal dynamics ofplasticity arising from this highly specialized sensorimo-tor training. DC-EEG reflects activation of the cerebral cor-tex caused by any afferent inflow. The neurophysiologicalbasis of this lowest frequency range of the EEG are excita-tory postsynaptic potentials in the dendrites of layers I-II[7]. DC-EEG has been shown to reflect cognitive andmotor processing [8,9]. Its spatial accuracy has been eval-uated by fMRI co-registration (spatial differences EEG-MRI < 12 mm [9]).

For the measurement of event-related DC-EEG (directvoltage electroencephalography), the auditory and

motoric features of piano performance were dissociated(labeled as auditory and motoric probe tasks): The probetasks during EEG required eitherpassive listeningorsilentfinger movement, and were therefore eitherpurely auditoryorpurely motoric.

In contrast, the trainingparadigm aimed at sensorimotorbindingby providing a regular piano situation with instantauditory feedback for each keystroke. The beginners weretrained to re-play acoustically presented melodies withtheir right hand as precisely as possible. The total trainingperiod for each subject consisted of 10 single 20-minute-sessions, two sessions a week, over a period of five to six

weeks.

The EEG probe task paradigm was carried out before thefirst practice session, right after the first practice session,after three weeks, and eventually after completion of thetraining, in order to evaluate changes that are introducedto the EEG as a result of the training paradigm.

Two groups of non-musicians were trained in the trainingparadigm and tested in the EEG probe task paradigm.Group 1 ('map' group) worked with a digital piano
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featuring a conventional key-to-pitch and force-to-loud-ness assignment.

Group 2 ('no-map' group) ran the same paradigm and thesame five-week training program but the five relevant

notes (pitches) were randomly reassigned to the five rele-vant keys, or fingers, respectively, after each single trainingtrial.

Additionally, nine professional pianists were tested in theEEG probe task paradigm.

ResultsEEG data were recorded immediately before and after the1st, after 5, and after 10 sessions of practice, in order totrace the changes induced by single session practice as wellas by the prolonged training.

The subjects' event-related slow EEG-potentials wererecorded at 30 electrode sites.

To exclude that a putative cortical motor DC activationaccompanying the auditory probe tasks generated anactual efferent, i.e. supra-threshold, outflow of motorcommands, a simultaneous EMG of the finger muscles ofthe right hand was monitored accompanying the EEG

while auditory stimuli were delivered.

The task-related DC shifts were baseline-corrected andchecked for consistency. A minimum of 45 trials withoutartifacts was required from each subject for averaging

purposes.

Mean values during the stimulus and the task period weresubjected to statistical analysis by repeated measure anal-

ysis of variance (ANOVA).

Longitudinal differences were obtained individually foreach subject, for the measurements right after the 1stses-sion, before the 6th, and at the beginning of the 11th ses-sion. Average data for all subjects was used to create aGrand Average. For longitudinal differences and groupdifferences a P< 0.05 criterion was applied. Behavioraldata was obtained from the same error measures that

served as level adaptation criterion during the interactivetraining (see Methods section for details). Values werenormalized, session-averaged, and group grand-averaged.

Fig. 1 depicts the Grand Average ('map' group, session 1,pre-training) of task-related EEG during the auditoryprobe task in a single electrode position (FC3) to exem-plify the evaluation procedure. The course of the obtainedaverage potential commenced with an evoked potential(N100) at the beginning of the stimulus period with itsmaximum amplitude over Cz reflecting an orienting

response to the initial note, followed by a positive poten-tial (P200). The following sustained negative DC-poten-tial shift during the 3-second task period plateaued afterabout 1 second, however, a fast N100-P200 response toeach single note of the auditory pattern was superimposedonto the DC-shift (every 600 ms).

The results of the topographic mapping of the sustainedDC values in the time window 1000 ms 3000 ms afterstimulus / movement onset are summarized in Fig. 2(auditory probe task) and Fig. 3 (motor probe task). Thedisplayed activation patterns are 'electrical top views' ontothe unfolded surface of the head (nose pointing upward,the lateral borders covering subtemporal electrodes level

with the ears).

Task-related potential at electrode position FC3 during thepresentation of the auditory probe taskFigure 1Task-related potential at electrode position FC3 dur-ing the presentation of the auditory probe task. Stim-ulus onset t = 0, stimulus end t = 3000 ms. Grand Averageincluding nine subjects ('map' group) with > 45 single presen-tations each. The averaging process preserves the interindi-vidually invariant signal components, such as the negative DCplateau and the superimposed ERP peaks (bimodal combina-tion at a latency of 100 ms/200 ms + n * 600 ms) that areevoked by the single tones the stimulus is composed of. Thetop of the shaded triangles indicate the DC level that isobtained by time-averaging the signal over 1-second timewindows; the resulting 30-electrode topographic interpola-tions are attached to the tips of the respective triangles. Sta-

tistical analysis and cortical imaging in the results section isbased on the time window [1000 ms, 3000 ms] after stimulusonset.
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EEG data was recorded immediately before and after the1st, 6th, and 11th session, in order to trace the changesinduced by single session practice as well as by the pro-longed training. For that purpose, the data obtainedbefore the 1stsession provided a subject's individual 'ini-tial state baseline' (Figs. 2a, 3a, both beginner groups).Compared to the baseline in Figs. 2a/3a, subtractive val-ues for the measurements right after the 1stsession (Figs.2b, 3b), before the 6th (Figs. 2c, 3c), and before the 11th

session (Figs. 2d, 3d), are depicted as shown. Figs. 2, 3(e)

show the task-related DC-activity of the professional pian-ists, to be compared to Figs. 2a, 3a.

DC-EEG: Auditory probe task

Figs. 2a,2b,2c,2d depict the 5-week changes of corticalactivation for the passive auditory paradigm. The largestamplitudes with respect to increase as well as decrease

were detected as follows: For the pre-training condition(Fig. 2a), the passive auditory musical processing led toactivation mainly in frontal and central areas. This wastrue for both beginner groups.

Initial alterations in cortical activity occurred after only 20minutes of practice (Fig. 2b). For the 'map' group, imme-diately following the very first session at the piano, passivelistening led to a widespread additional activation in the

vicinity of the central sulcus (as estimated by comparisonwith Fig. 3a) and lateralized to the left. (Only the righthand had been trained). The subsequent measurements

(Figs. 2c,2d) were collected before the 6th/ 11th trainingsession, i.e. the probe tasks were conducted immediatelybefore (instead of after) the attentionally loaded practice

session. The interval to the preceding active training was

3.9 2.9 days ( SD). Thus, what we would expectfrom this data are stable phenomena. After 5 sessions(20.5 7.9 days of practice, Fig. 2c), the additional left-lateralized coactivation gradually focused onto the leftprimary sensorimotor cortex.

After 10 sessions (38.7 11.6 days of practice, Fig. 2d), aclear co-activation of the sensorimotor cortex responsiblefor the right hand, accompanied by activity in rightfronto-temporal electrodes, was observed. In neither con-

Changes of cortical DC-potentials induced by training: Auditory probe taskFigure 2Changes of cortical DC-potentials induced by training: Auditory probe task. The displayed activation patterns are'electrical top views' onto the unfolded surface of the head. Electrode positions are indicated by white dots, the color valuesresult from interpolation including the four nearest electrodes for each pixel. (a) Initial DC-EEG in the 17 inexperienced sub-jects prior to first practice. Normalized data. (b) Activation changes (additional negative potential compared to the baseline (a))after the first 20-minute practice. (c) Activation changes after 20.5 7.9 days of practice (5 sessions). (d) Activation changesafter 38.7 11.6 days of practice (10 sessions). (e) group of 9 professional pianists (accumulated practice time = 19.4 6.7years) while performing the identical experimental paradigm. Normalized data. In (b), (c), and (d): Upper panel: Beginner group1 ('map' group, n = 9), lower panel: Beginner group 2 ('no-map' group, n = 8). Subtractive data based on individual potential dif-ferences. (f) Color scale for normalized panels (a) and (e); (g) Color scale for subtractive panels (b) through (d).

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dition did the EMG reveal any muscular activity in the dig-its of the right hand.

The initial parietal activity was reduced. Moreover, the

frontal activity showed a salient region in the righthemisphere.

The 'no-map' group displayed non-homogeneous resultswith a tendency to additional activity in parietal regionsthat did not change profoundly over the weeks of training.However, interindividual variance was high throughoutthe data (group standard deviations of an order of magni-tude 1 V at single electrode sites for potential averages

with a range of only 5 V). Whilst the above resultsremain on a merely descriptive level, we found highly sig-nificant changes for the electrode positions C3 (left cen-tral) and F10 (right fronto-temporal) in the 'map' group

only.

The EEG activation pattern of the professional pianists(Fig. 2e) exhibits activity over frontal, bilateral temporaland central areas. The pattern differs significantly (P

bangert, m., & altenmüller, e. o. (2003). mapping perception to action in piano practice- a...

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