Affiliations: Wellcome Department of Imaging Neuroscience, 12 Queen
Square, London, WC1N 3BG, UK | Department of Neurology,
Christian-Albrechts-University, Kiel, Germany | NeuroImageNord Kiel-Hamburg-Lübeck at Hamburg
University Hospital, Hamburg, Germany
Note: [] Corresponding author: Dr. Lucy Lee, Wellcome Department of
Imaging Neuroscience, 12 Queen Square, London, WC1N 3BG, UK. Tel.: +44
2078337480; Fax: +44 2078131420; E-mail: llee@fil.ion.ucl.ac.uk
Abstract: This paper reviews the effects of single and repetitive transcranial
magnetic stimuli (rTMS) delivered to one cortical area and measured across
distributed brain regions using electrophysiological measures (e.g. motor
thresholds, motor evoked potentials, paired-pulse stimulation), functional
neuroimaging (including EEG, PET and fMRI) and behavioural measures. Discussion
is restricted to changes in excitability in the primary motor cortex and
behaviour during motor tasks following transcranial magnetic stimulation
delivered to primary motor and premotor areas. Trains of rTMS have lasting
effects on the excitability of intrinsic and corticofugal neurones, altering
the responsiveness of local and remote sites. These effects lead to distributed
changes in synaptic activity at rest, and during a range of motor tasks. It is
possible to impair or improve performance following rTMS, but for most simple
motor tasks performance is unaltered. Changes in distributed activity observed
with functional imaging during motor behaviour may represent compensatory
activity, enabling maintenance of performance; stimulation of additional
cortical areas appears to impair performance. A detailed understanding of the
distributed changes in excitability following rTMS may facilitate future
attempts to modulate motor behaviour in the healthy brain and for therapeutic
purposes.
