Improvement of tactile discrimination performance and enlargement of cortical somatosensory maps after 5 Hz rTMS.
Repetitive transcranial magnetic stimulation (rTMS) is increasingly used to investigate mechanisms of brain functions and plasticity, but also as a promising new therapeutic tool. The effects of rTMS depend on the intensity and frequency of stimulation and consist of changes of cortical excitability, which often persists several minutes after termination of rTMS. While these findings imply that cortical processing can be altered by applying current pulses from outside the brain, little is known about how rTMS persistently affects learning and perception. Here we demonstrate in humans, through a combination of psychophysical assessment of two-point discrimination thresholds and functional magnetic resonance imaging (fMRI), that brief periods of 5 Hz rTMS evoke lasting perceptual and cortical changes. rTMS was applied over the cortical representation of the right index finger of primary somatosensory cortex, resulting in a lowering of discrimination thresholds of the right index finger. fMRI revealed an enlargement of the right index finger representation in primary somatosensory cortex that was linearly correlated with the individual rTMS-induced perceptual improvement indicative of a close link between cortical and perceptual changes. The results demonstrate that repetitive, unattended stimulation from outside the brain, combined with a lack of behavioral information, are effective in driving persistent improvement of the perception of touch. The underlying properties and processes that allow cortical networks, after being modified through TMS pulses, to reach new organized stable states that mediate better performance remain to be clarified.
Tegenthoff
Martin
M
Department of Neurology, Ruhr-University Bochum, BG-Kliniken Bergmannsheil, Bochum, Germany.
Ragert
Patrick
P
Pleger
Burkhard
B
Schwenkreis
Peter
P
Förster
Ann-Freya
AF
Nicolas
Volker
V
Dinse
Hubert R
HR
D000328:Adult; D000704:Analysis of Variance; D001921:Brain / Q000378:metabolism; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000378:metabolism*; D004192:Discrimination, Psychological; D004558:Electric Stimulation; D004594:Electrophysiology; D019054:Evoked Potentials, Motor; D005073:Evoked Potentials, Somatosensory; D007839:Functional Laterality; D006801:Humans; D017774:Long-Term Potentiation; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008280:Magnetics; D008297:Male; D009044:Motor Cortex; D010100:Oxygen / Q000378:metabolism; D010465:Perception; D013003:Somatosensory Cortex / Q000378:metabolism; D013997:Time Factors; D014110:Touch
D010100:Oxygen