Transcranial magnetic stimulation

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1. What is Transcranial magnetic stimulation (TMS)? 1

  • TMS is a technique for noninvasive stimulation of the human brain.
  • Stimulation is produced by generating a brief, high-intensity magnetic field by passing a brief electric current through a magnetic coil. The field can excite or inhibit a small area of brain below the coil.
  • All parts of the brain just beneath the skull can be influenced, but most studies have been of the motor cortex where a focal muscle twitch can be produced, called the motor-evoked potential.
  • The technique can be used to map brain function and explore the excitability of different regions. Brief interference has allowed mapping of many sensory, motor, and cognitive functions.
  • TMS has some clinical utility, and, because it can influence brain function if delivered repetitively, it is being developed for various therapeutic purposes.

2. How good is TMS? 2

  • TMS primarily targets the gyri at the hemispheric surface due to limited depth penetration.
  •  The direct response to TMS is complex, involving a mixture of neuronal populations.
  •  Myelinated axon terminals of pyramidal cells and inhibitory interneurons in the crown of the gyri
  • constitute low-threshold targets for TMS.
  •  Neuronal excitation propagates along axons and across synapses from the primary stimulation site to
  • connected regions in a state-dependent fashion.
  •  TMS always causes substantial peripheral somatosensory and auditory co-stimulation

3. Highly cited TMS studies 3

  1. TMS to probe integrity of the corticospinal tract
  2. TMS to probe motor cortical excitability
  3. TMS to probe cognitive processes
  4. rTMS to induce long-term change of excitability
  5. TBS for long-term up- and down-regulation of cortical excitability
  6. Focal TMS to map training-induced representational reorganization of motor cortex in stroke patients
  7. Pharmaco-TMS to characterize TMS measures of motor cortical excitability
  8. HF-rTMS increases motor excitability as a function of frequency and intensity
  9. Focal TMS to map practice-dependent palsticity in human motor cortex
  10. rTMS to treat brain disorders
  1. Hallett, Mark. “Transcranial magnetic stimulation: a primer.” Neuron 55, no. 2 (2007): 187-199. ↩︎
  2. Siebner, Hartwig R., Klaus Funke, Aman S. Aberra, Andrea Antal, Sven Bestmann, Robert Chen, Joseph Classen et al. “Transcranial magnetic stimulation of the brain: What is stimulated?–A consensus and critical position paper.” Clinical Neurophysiology 140 (2022): 59-97. ↩︎
  3. Ziemann, Ulf. “Thirty years of transcranial magnetic stimulation: where do we stand?.” Experimental brain research 235.4 (2017): 973-984 ↩︎

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