Study recommends lowering the dosage of magnetic stimulation for mental illness
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Study recommends lowering the dosage of magnetic stimulation for mental illness

Israeli, German researchers say brain neurons ‘get tired’ when stimulated too fast and cease to respond to noninvasive rTMS brain therapy

The rTMS coil is placed near the head and pulses of currents (yellow) are transmitted through it. These pulses generate a magnetic field which excites neurons in a specific spot in the brain, allowing for non-invasive treatment. (Prof. Ido Kanter, Bar Ilan University)
The rTMS coil is placed near the head and pulses of currents (yellow) are transmitted through it. These pulses generate a magnetic field which excites neurons in a specific spot in the brain, allowing for non-invasive treatment. (Prof. Ido Kanter, Bar Ilan University)

A promising noninvasive brain treatment, repetitive transcranial magnetic stimulation (rTMS), is used to treat depression, effects of a stroke, multiple sclerosis and movement disorders by transmitting pulses to a patient’s brain via a magnetic coil placed near the head.

This type of magnetic brain therapy has been deemed valuable in the treatment of these conditions, and in some countries is covered by health insurance packages.

However, one of the main challenges in using this treatment is determining the timing of the pulses.

Now, Israeli physicists and a group of German neurologists suggest that fewer stimulations of the brain are preferable, since neurons “get tired” when stimulated too fast and subsequently cease to respond to brain stimulation therapy.

The researchers published their findings in online article Frontiers in Neuroscience.

Following a series of new experiments and advanced theoretical studies, the Israeli physicists, led by Prof. Ido Kanter of the Department of Physics and Gonda (Goldschmied) Multidisciplinary Brain Research Center at Bar-Ilan University, have demonstrated that each neuron has a maximal firing rate that is much lower than previously assumed. Neuron firing is the communication that takes place between neurons, through electrical impulses and neurotransmitters.

Hence, when stimulated too fast, neuronal response failures occur. “Neurons are like people,” said Prof. Kanter. “Stuttering occurs when we speak too fast, errors occur when we type too fast, and confusion emerges when we learn too fast.”

The researchers evaluated a variety of existing rTMS scheduling protocols and found there were “conflicting results and no clear guideline for the temporal organization of brain stimulations,” said Prof. Kanter. “Our findings suggest that slower rates of stimulation may be more effective in brain therapy, and we suggest that this method be adopted in order to maximize effective brain therapy.”

That is because the brain, unlike computers, is composed of unreliable elements, he said.

“While modern computers are composed of very reliable elements, the brain is composed of unreliable elements, since neurons ‘tire’ and frequently fail to respond,” Kanter said.

rTMS equipment and trained therapists are becoming more accurate and effective in the localization and real-time tracking of stimulation spots in the brain, the researchers said.

However, without understanding how to optimize the stimulation scheduling, the efficiency of the therapy will remain limited, they said. The proposed mechanism of “less is more” is one of the first guidelines toward improving this type of noninvasive therapy, they said.

The research was conducted in collaboration with a group of neurologists led by Prof. Dr. Walter Paulus, from the Department of Clinical Neurophysiology, University Medical Center Göttingen and his team, including Dr. Islam Halawa and Dr. Yuichiro Shirota.

This research is supported in part by the TELEM grant of the Council for Higher Education of Israel.

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