Transcranial magnetic stimulation: new insights into representational cortical plasticity |
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Authors: | Hartwig Siebner John Rothwell |
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Institution: | (1) Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, 8–11 Queen Square, London WC1N 3BG, UK, |
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Abstract: | In the last decade, transcranial magnetic stimulation (TMS) has been used increasingly as a tool to explore the mechanisms
and consequences of cortical plasticity in the intact human cortex. Because the spatial accuracy of the technique is limited,
we refer to this as plasticity at a regional level. Currently, TMS is used to explore regional reorganization in three different
ways. First, it can map changes in the pattern of connectivity within and between different cortical areas or their spinal
projections. Important examples of this approach can be found in the work on motor cortex representations following a variety
of interventions such as immobilization, skill acquisition, or stroke. Second, TMS can be used to investigate the behavioural
relevance of these changes. By applying TMS in its "virtual lesion" mode, it is possible to interfere with cortical function
and ask whether plastic reorganization within a distinct cortical area improves function. Third, TMS can be used to promote
changes in cortical function. This is achieved by using repetitive TMS (rTMS) to induce short-term functional reorganization
in the human cortex. The magnitude and the direction of rTMS-induced plasticity depend on extrinsic factors (i.e. the variables
of stimulation such as intensity, frequency, and total number of stimuli) and intrinsic factors (i.e. the functional state
of the cortex targeted by rTMS). Since conditioning effects of rTMS are not limited to the stimulated cortex but give rise
to functional changes in interconnected cortical areas, rTMS is a suitable tool to investigate plasticity within a distributed
functional network. Indeed, the lasting effects of rTMS offer new possibilities to study dynamic aspects of the pathophysiology
of a variety of diseases and may have therapeutic potential in some neuropsychiatric disorders.
Electronic Publication |
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Keywords: | Representational plasticity Human cortex Imaging Mapping Repetitive transcranial magnetic stimulation |
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