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4 - Practice-induced plasticity in the human motor cortex
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- By Joseph Classen, Human Cortical Physiology Laboratory, Department of Neurology, Bayerische Julius-Maximilians Universität, Würzburg, Germany, Leonardo G. Cohen, Human Cortical Physiology Section, NINDS, National Institutes of Health, Bethesda, MD, USA
- Edited by Simon Boniface, Ulf Ziemann, Johann Wolfgang Goethe-Universität Frankfurt
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- Book:
- Plasticity in the Human Nervous System
- Published online:
- 12 August 2009
- Print publication:
- 15 May 2003, pp 90-106
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Summary
Introduction
It is common knowledge that ‘practice makes perfect’. Many types of human motor behaviour seem to rely heavily on the fact that the performance of subsequent movements is facilitated by prior performance of similar movements. Therefore, the capacity to build a memory trace of previously practised movements appears to be a fundamental property of the human motor system. Recent studies have focused on this theme in an attempt to gain insight into the physiology of motor memory. Such understanding may contribute to the development of techniques to promote recovery of function following brain damage in humans.
Use-dependent plasticity
Since the 1990s, numerous reports, by employing TMS, demonstrated plasticity induced by motor learning, motor practice or use. One of the earliest reports showed that the excitability of the muscle representation of the ‘reading’ finger is increased in Braille readers (Pascual-Leone et al., 1993). Pearce and coworkers found that, in highly trained Olympic badminton players, the excitability of the first dorsal interosseus muscle of the skilled hand is increased and its topographical representation is altered when compared to the unskilled hand or to the representations in untrained players (Pearce et al., 2000). These studies provided evidence that the organization of motor activity is modifiable. They also raised questions about the particular factors involved in long-term practice that were instrumental in triggering these profound changes.
6 - Stimulation-induced plasticity in the human motor cortex
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- By Joseph Classen, Human Cortical Physiology and Motor Control Laboratory, Department of Neurology, Bayerische Julius-Maximilians Universität, Würzburg, Germany, Ulf Ziemann, Clinic of Neurology, J.W. Goethe-University Frankfurt am Main, Germany
- Edited by Simon Boniface, Ulf Ziemann, Johann Wolfgang Goethe-Universität Frankfurt
-
- Book:
- Plasticity in the Human Nervous System
- Published online:
- 12 August 2009
- Print publication:
- 15 May 2003, pp 135-165
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- Chapter
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Summary
Introduction
Neuronal plasticity may be defined as any functional change within the nervous system outlasting an (experimental) manipulation. Plasticity, by this definition, does not comprise structural changes, such as those occurring during development or repair. Although there is no universally accepted lower limit of its duration, the term ‘plasticity’ is usually only applied when neuronal changes outlast the manipulation by more than a few seconds. In experimental animals, as well as in humans, plasticity is usually defined neurophysiologically by changes in the stimulus–response characteristics (‘excitability’).
Plasticity of the central nervous system has attracted much interest because it is thought to be related to the mechanisms underlying the formation of memories and the learning of new skills. Very likely, it is also involved in restoration of brain function after its initial loss as a consequence of brain injury. Neuronal plasticity may be induced internally, such as by practising movements (see Chapter 4), or externally, for instance, by limb amputation, spinal cord injury or cerebral stroke (see Chapter 8), or by repetitive electrical or magnetic neuronal stimulation, as reviewed here. Models of plasticity relying on external stimulation may be attractive because they allow best to control for experimental conditions. Human models of central nervous system plasticity may contribute particularly relevant information to the understanding of fundamental principles of plasticity. Additionally, the neuronal changes induced in human models of plasticity may themselves prove to be therapeutically useful.