J Med Assoc Thai 2009; 92 (11):1560

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Basic Principle of Transcranial Magnetic Stimulation
Auvichayapat P Mail, Auvichayapat N

Background: Transcranial Magnetic Stimulation (TMS) is a new neurophysiological technique based on the
principle of electromagnetic induction. When a pulse of current passes through a coil, it becomes a magnetic
field and penetrates the scalp and skull, and reach the brain painlessly.

Objective: Review TMS stimulator, types of stimulation, mechanism of action, and its application.

Material and Method:
There are three types of TMS stimulation: 1) Single pulse; used in studying of
motor threshold and phosphene threshold. 2) Paired pulse; used in the study of intracortical inhibitory and
facilitatory mechanisms. 3) Repetitive stimulation; changes corticospinal/corticocortical pathway.

Results: The mechanisms increases activity of synapse, changes the secretion of neurotransmitter, and causes
neuronal plasticity or long-term potentiation. Repetitive stimulation is used in fundamental basic science
for brain mapping. It is a new therapeutic method for neuro-psychiatic disorders that does not respond to
medications.

Conclusion:
TMS study is rapidly increasing and accepted as a noninvasive technique. The most favorable
treating outcomes are depression and Parkinson disease. Other neuro-psychiatic therapeutic outcomes are
ongoing.

Keywords: Transcranial Magnetic Stimulation, TMS, Neurophysiologic technique, neuro-psychiatic disorders

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