The TMS Map Scales with Increased Stimulation Intensity and Muscle Activation.
One way to study cortical organisation, or its reorganisation, is to use transcranial magnetic stimulation (TMS) to construct a map of corticospinal excitability. TMS maps are reported to be acquired with a wide variety of stimulation intensities and levels of muscle activation. Whilst MEPs are known to increase both with stimulation intensity and muscle activation, it remains to be established what the effect of these factors is on the map's centre of gravity (COG), area, volume and shape. Therefore, the objective of this study was to systematically examine the effect of stimulation intensity and muscle activation on these four key map outcome measures. In a first experiment, maps were acquired with a stimulation intensity of 110, 120 and 130% of resting threshold. In a second experiment, maps were acquired at rest and at 5, 10, 20 and 40% of maximum voluntary contraction. Map area and map volume increased with both stimulation intensity (P < 0.01) and muscle activation (P < 0.01). Neither the COG nor the map shape changed with either stimulation intensity or muscle activation (P > 0.09 in all cases). This result indicates the map simply scales with stimulation intensity and muscle activation.
NIHR Surgical Reconstruction and Microbiology Research Centre, School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Edgbaston, B15 2TT, UK.|MRC-ARUK Centre for Musculoskeletal Ageing Research, School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, B15 2TT, UK.
Mark
M
van de Ruit
NIHR Surgical Reconstruction and Microbiology Research Centre, School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Edgbaston, B15 2TT, UK. m.j.grey@bham.ac.uk.|MRC-ARUK Centre for Musculoskeletal Ageing Research, School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, B15 2TT, UK. m.j.grey@bham.ac.uk.
Michael J
MJ
Grey
D000328:Adult; D001931:Brain Mapping; D016009:Chi-Square Distribution; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D011601:Psychophysics; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
Corticospinal excitability; Mapping; Muscle activation; Stimulation intensity; TMS