Learning to play a musical instrument is known to involve both structural and functional changes in the brain. Studies published in recent years have established, for example, that professional keyboard players have increased gray matter volume in motor, auditory and visual parts of the brain, and that violinists have a larger somatosensory cortical representation of the left hand than do non-musicians.
Musical training is a complex process involving simultaneously perceiving the inputs from the senses of hearing, sight and touch, as well as co-ordinating these with the outputs of the motor system. It therefore provides neuroscientists with a good model to study the effects of neural plasticity in different sensory systems. To date, however, researchers have not compared the effects of different types of musical training on neural plasticity.
A German group investigating this phenomenon now shows that piano training involving playing musical sequences leads to more reorganizational changes in the brain than does training involving listening alone. They also demonstrate that just 2 weeks of cross-modal musical training enhances connectivity between the sensorimotor and auditory regions of the brain. Their findings are published in the current issue of the Journal of Neuroscience.
Claudia Lappe and her colleagues of the Institute of Biomagnetism and Biosignal Analysis at the University of Münster in Germany recruited 23 participants for their study, none of whom had undergone any musical training other than compulsory school lessons. The participants were first presented with one three-tone and another six-tone piano sequence, and their ability to discriminate between the two was assessed using magnetoencephalography (MEG) to measure activity in the auditory parts of the brain. Over a period of 2 weeks, one group of participants was then taught to play a musical sequence on the piano, while the other merely listened to the music played by the participants. Both groups were then tested again for their ability to make judgements about the same piano sequences they had listened to at the beginning.
People with musical expertise or any degree of musical training are better able to discriminate between muscial tones than those who are not. This ability can be detected by measurements of the electrical signals produced by the brain, as a change in the activity in the auditory cortex that occurs between 1 and 2 tenths of a second after the presentation of stimuli which include small changes in the frequency or intensityof a sound. This so-called musically elicited mismatch negativity (MMNm) is what Lappe’s team used to determine the extent of cortical plasticity induced by musical training in their participants.
Each group of participants in the study underwent training of a different kind. One group’s training involved listening to the piano sequences initially presented to them by the researchers and to those played by the other group. This is unimodal training, as it engaged only the auditory regions of the brain. By contrast, the other group’s training involved both listening to piano sequences and generating their own. This is multimodal training, as it requires the activity of not only the auditory regions of the brain but also the motor cortex, which generates movements, and those regions that integrate the sensory inputs with the motor activity.
When the pre- and post-training results were analyzed, the MEG recordings showed a significant increase in the amplitude of the MMNm in those participants who underwent multimodal training compared to those who underwent unimodal training. Although the performance of both groups on the discrimination task improved significantly, the participants in the multimodal training group exhibited a much larger enhancement than those in the unimodal training group. This effect of training was also found to be more pronounced in the right hemisphere than in the left.
This study shows that sensorimotor and auditory training induces cortical reorganization to a greater extent than does auditory training alone. It also shows that sensorimotor and auditory training cause more changes in the auditory cortex than auditory training alone. This phenomemon, called cross-modal plasticity, has been investigated only rarely. In 2003, the same group showed that professional trumput players have enhanced interactions between the auditory cortex and the regions of the somatosensory cortex devoted to the lip. The new study therefore provides another demonstration that the sensorimotor and auditory cortices are connected to each other.
It is generally agreed that hearing music makes people want to move – synchronized movements in response to music are observed in all cultures, and the relationship between the two may have its origins in the rhythmic movements required for locomotion. This study adds to a growing body of evidence which suggests that the reverse may also be true, as it shows that movements and the sensorimotor activity associated with them can affect the processing of auditory information.
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Lappe, C. et al (2008). Cortical plasticity induced by short-term unimodal and multimodal musical training. J. Neurosci. 28: 9632-9639. DOI: 10.1523/JNEUROSCI.2254-08.2008