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TMS terminology

Many of the listed explanations are intended for those who are not familiar with TMS technology.

Modes of magnetic stimulation
Related to experiments
Related to instrumentation

Modes of magnetic stimulation (indicative):

MSgeneral term for magnetic stimulation, including TMS and stimulation of the peripheral nervous system
TMSgeneral term for all modes of transcranial magnetic stimulation
rTMSrepetitive magnetic stimulation
single-pulse TMSnon-repetitive TMS
low-frequency TMS
slow TMS
repetition rate below 1 Hz
high-frequency TMS
rapid-rate TMS
repetition rate above 1 Hz
dual-pulse TMS
paired-pulse TMS
stimulation with two distinct stimuli through the same coil at a range of different intervals; the intensities can be varied independently
quadruple-pulse TMSas dual-pulse stimulation, but with 4 pulses
double TMSstimulation with two stimulation coils applied to different cerebral loci; the timing and stimulus intensity are adjusted separately
multichannel TMSTMS with multiple (say, 20-100) coils that are independently controlled
TMS mappingperformed by changing the coil position above the head while observing its effects

Related to experiments:

EMGelectromyography, recording of electrical activity associated with muscle movements
MEPmotor-evoked potential; an excitatory response to TMS
kindlingseizure induction with many subconvulsive stimuli; has never been observed in TMS or rTMS
silent periodan inhibitory response to TMS; a period after the stimulus during which a second stimulus is ineffective
threshold intensitythe smallest intensity of TMS that causes measurable responses

Related to instrumentation:

8-shaped coil (also: buttefly, figure-of-eight, double)a stimulating coil with two planar wings with opposing current directions; induces a better focused electric field than a circular coil
coil current ithe current circulating in the coil; typically one (biphasic) or more (oscillating) sinusoidal pulses
current rise timerise time of the coil current from zero to peak, often around 70-100 ms
electric field Enerves are excited with E, which is induced by a changing B; hence, pulsed magnetic fields are needed for nervous excitation
magnetic field BThe tissue is entirely transparent to B and hence the intensity of B does not describe the efficacy of stimulation; often about 2 tesla on the coil surface and 0.5 T in the cortex
rate of change of current di/dtmaximum occurs always in the beginning of the current pulse, being equal to capacitor voltage or coil inductance; typically, 150 A/ms
stimulator outputoften expressed in % of the maximum output; should be used cautiously, since output varies among stimulator units
thyristora semiconductor switch capable of handling high peak currents in a short time; used to discharge the power capacitor trough the coil


Original content by Jarmo Ruohonen, updated and converted to HTML 4.0 by Jussi Nurminen

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