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The History of Bioelectromagnetism

According to these fundamental approaches, TMS of the motor cortex gradually obtained interest. In

parallel, Anthony Tony Barker, professor at the University of Shefeld, Teaching Hospital’s Department

of Medical Physics and Clinical Engineering, and his co-workers stimulated successfully superfcial

nerves via magnetic felds by placing the stimulation coils on the human head and proposed a prototype

of a magnetic stimulator for peripheral nerve stimulation (Barker et al., 1985, 1987). Tey used 2 ms

duration pulses of time-varying magnetic felds to induce electric currents in the brain and recorded

for the frst time motor-evoked potentials obtained by median nerve magnetic stimulation with circular

single coils. As the frst clinical examinations, Barker’s group developed the frst TMS device which

produces cortical depolarization via magnetic stimulation in 1986 (Barker et al., 1986). Tis was the

beginning of magnetic brain stimulation in clinical examinations. Tese early researches used circular

single coils. Placing these circular single coils on the head and passing a current pulse through it. Eddy

currents were induced in the head, which stimulates broad areas of the brain. Since then, the TMS has

become a popular technique in the research of brain activity because it is easy to use as a non-invasive

tool (Barker, 1991; Ueno and Sekino, 2014; Ueno et al., 2019). TMS is a non-invasive and efective method

of cortical stimulation for medical diagnosis, in particular for studying the function of the human

brain. Tis method is based on the utilization of time-varying magnetic felds. Wassermann described

the basic principles of TMS as follows:

TMS uses the principle of inductance to get electrical energy across the scalp and skull without the

pain of direct percutaneous electrical stimulation. It involves placing a small coil of wire on the

scalp and passing a powerful and rapidly changing current through it. Tis produces a magnetic

feld that passes unimpeded and relatively painlessly through the tissues of the head. Te peak

strength of the magnetic feld is related to the magnitude of the current and the number of turns of

wire in the coil. Te magnetic feld, in turn, induces a much weaker electrical current in the brain.

Te strength of the induced current is a function of the rate of change of the magnetic feld, which

is determined by the rate of change of the current in the coil. In order to produce enough current to

excite neurons in the brain, the current passed through the coil must change within a few hundred

microseconds.

Wassermann (1998)

Depending on the parameters of stimulation such as frequency, duration and magnetic feld strength,

TMS is subdivided into two repetitive TMS (rTMS) treatments: low-frequency (1 Hz or less) rTMS and

high-frequency rTMS with frequencies from 5 to 20 Hz. Te former leads to reduction of excitability,

and the latter is considered to produce an excitatory efect. Te rTMS was frst produced by Cadwell

Laboratories in 1988. In 2008, rTMS was frst approved for clinical treatments of patients with major

depression by the US Food and Drug Administration (FDA). Te FDA guidelines for rTMS were updated

in 2011 (Lin, 2016). Now, TMS has become a tool in basic neuroscience investigations, therapeutic and

rehabilitation applications such as depression, Parkinson’s disease (PD), Alzheimer’s disease, stroke,

pain, etc. (Kadosh, 2014). In 2017, Barker received “Te First International Brain Stimulation Award”

for his outstanding contributions in developing TMS at the Conference in Barcelona. Tis International

Conference award was given by publisher Elsevier.

2.5.3 Others

Afer constructing his frst large telescope in 1774, Frederick William Herschel (1738–1822), a German-

born British astronomer and composer, while measuring the thermal efects of sunlight with a prism

observed the infrared radiation from the spectrum of sunlight by means of a glass thermometer in 1800.

André Marie Ampère in 1835 confrmed that this infrared radiation has shorter wavelengths of elec­

tromagnetic waves. Infrared radiation is ofen divided into three regions according to the ISO: 20473,

which specifes the following: near-infrared (NIR) with wavelengths of 0.78–3 μm, mid-infrared with