Yiftach Roth1, Gaby S Pell1, Noam Barnea-Ygael2, Moria Ankry3, Yafit Hadad3, Ami Eisen4, Yuri Burnishev4, Aron Tendler5, Elisha Moses4, Abraham Zangen6. 1. Brainsway Ltd, Israel; Department of Life Sciences, Ben-Gurion University, Beer Sheva, Israel. 2. Department of Life Sciences, Ben-Gurion University, Beer Sheva, Israel. 3. Brainsway Ltd, Israel. 4. The Department of Physics of Complex Systems, The Weizmann Institute of Science, Rehovot, Israel. 5. Brainsway Ltd, Israel; Department of Life Sciences, Ben-Gurion University, Beer Sheva, Israel; Advanced Mental Health Care Inc., Israel. 6. Department of Life Sciences, Ben-Gurion University, Beer Sheva, Israel. Electronic address: azangen@bgu.ac.il.
Abstract
BACKGROUND: Transcranial magnetic stimulation (TMS) is a rapidly expanding technology utilized in research and neuropsychiatric treatments. Yet, conventional TMS configurations affect primarily neurons that are aligned parallel to the induced electric field by a fixed coil, making the activation orientation-specific. A novel method termed rotational field TMS (rfTMS), where two orthogonal coils are operated with a 90° phase shift, produces rotation of the electric field vector over almost a complete cycle, and may stimulate larger portion of the neuronal population within a given brain area. OBJECTIVE: To compare the physiological effects of rfTMS and conventional unidirectional TMS (udTMS) in the motor cortex. METHODS: Hand and leg resting motor thresholds (rMT), and motor evoked potential (MEP) amplitudes and latencies (at 120% of rMT), were measured using a dual-coil array based on the H7-coil, in 8 healthy volunteers following stimulation at different orientations of either udTMS or rfTMS. RESULTS: For both target areas rfTMS produced significantly lower rMTs and much higher MEPs than those induced by udTMS, for comparable induced electric field amplitude. Both hand and leg rMTs were orientation-dependent. CONCLUSIONS: rfTMS induces stronger physiologic effects in targeted brain regions at significantly lower intensities. Importantly, given the activation of a much larger population of neurons within a certain brain area, repeated application of rfTMS may induce different neuroplastic effects in neural networks, opening novel research and clinical opportunities.
BACKGROUND: Transcranial magnetic stimulation (TMS) is a rapidly expanding technology utilized in research and neuropsychiatric treatments. Yet, conventional TMS configurations affect primarily neurons that are aligned parallel to the induced electric field by a fixed coil, making the activation orientation-specific. A novel method termed rotational field TMS (rfTMS), where two orthogonal coils are operated with a 90° phase shift, produces rotation of the electric field vector over almost a complete cycle, and may stimulate larger portion of the neuronal population within a given brain area. OBJECTIVE: To compare the physiological effects of rfTMS and conventional unidirectional TMS (udTMS) in the motor cortex. METHODS: Hand and leg resting motor thresholds (rMT), and motor evoked potential (MEP) amplitudes and latencies (at 120% of rMT), were measured using a dual-coil array based on the H7-coil, in 8 healthy volunteers following stimulation at different orientations of either udTMS or rfTMS. RESULTS: For both target areas rfTMS produced significantly lower rMTs and much higher MEPs than those induced by udTMS, for comparable induced electric field amplitude. Both hand and leg rMTs were orientation-dependent. CONCLUSIONS:rfTMS induces stronger physiologic effects in targeted brain regions at significantly lower intensities. Importantly, given the activation of a much larger population of neurons within a certain brain area, repeated application of rfTMS may induce different neuroplastic effects in neural networks, opening novel research and clinical opportunities.