Effects of 30 Hz Theta Burst Transcranial Magnetic Stimulation on the primary motor cortex
ABSTRACT Theta Burst Stimulation (TBS) is a relatively new form of repetitive Transcranial Magnetic Stimulation (TMS) used to probe neuroplasticity in the human cortex. Thirty-Hz TBS, a variation of the originally described 50Hz TBS, has been shown to induce cortical changes in several nonmotor regions. However, its effects over the primary motor cortex have not been examined. Due to TMS device mechanical properties, 30Hz TBS is advantageous over 50Hz TBS in that it can be delivered at higher stimulation intensities. The goal of this pilot study is to examine the neurophysiologic effects of 30Hz TBS on the primary motor cortex (M1) of healthy adults. Eighteen right-handed adults (33±9.0 years; M:F=8:10) completed intermittent TBS (iTBS) or continuous TBS (cTBS) over left M1. TBS was performed with Magstim® SuperRapid2 with stimulation bursts (3 pulses at 30Hz) repeating every 200ms. For iTBS, each 2-s stimulation train was separated by 8s but there was no pause between trains for cTBS. Each TBS consisted of a total of 600 pulses delivered at an intensity of 90%*Resting Motor Threshold. Motor-Evoked Potentials (MEP) in the right first dorsal interosseous muscle were measured before, and one and ten minutes after TBS. Pre/post-TBS MEP amplitudes were compared using repeated-measures ANOVA. MEP amplitudes increased after 30Hz iTBS and decreased after 30Hz cTBS (TBS-Type*Time effect p=0.009). In conclusion, 30Hz TBS induced similar neurophysiologic effects over M1 as conventional 50Hz TBS.
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ABSTRACT: Fourteen healthy children (13.8 ± 2.2 years, range 10-16; M:F = 5:9) received 30 Hz intermittent theta burst transcranial magnetic stimulation (iTBS) with a stimulation intensity of 70% of resting motor threshold (RMT) with a total of 300 (iTBS300) pulses. All volunteers were free of neurologic, psychiatric and serious medical illnesses, not taking any neuropsychiatric medications, and did not have any contraindications to transcranial magnetic stimulation. Changes in the mean amplitudes of motor-evoked potentials from baseline following iTBS were expressed as a ratio and assessed from 1 to 10 min (BLOCK1) and 1-30 min (BLOCK2) using repeated-measures analysis of variance. All 14 subjects completed iTBS300 over the dominant primary motor cortex (M1) without any clinically reported adverse events. ITBS300 produced significant M1 facilitation [F (5, 65) = 3.165, p = 0.01] at BLOCK1 and trend level M1 facilitation at BLOCK2 [F (10, 129) = 1.69, p = 0.089]. Although iTBS300 (stimulation duration of 92 s at 70% RMT) delivered over M1 in typically developed children was well-tolerated and produced on average significant facilitatory changes in cortical excitability, the post-iTBS300 neurophysiologic response was variable in our small sample. ITBS300-induced changes may represent a potential neuroplastic biomarker in healthy children and those with neuro-genetic or neuro-psychiatric disorders. However, a larger sample size is needed to address safety and concerns of response variability.Frontiers in Human Neuroscience 01/2015; 9(91). DOI:10.3389/fnhum.2015.00091 · 2.90 Impact Factor
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ABSTRACT: Stroke induces structural and functional changes within the cortical motor network of both hemispheres. Repetitive transcranial magnetic stimulation modulates the excitability of the motor cortex and thereby may facilitate motor function and/or recovery of motor function after stroke. Based on a systematic literature search we identified 33 placebo-controlled trials which examined the effectiveness of repetitive transcranial magnetic stimulation in the treatment of impaired hand function following stroke. Despite limitations, the majority of the studies referred to the interhemispheric competition model after stroke to apply repetitive transcranial magnetic stimulation. In a comparative approach, methodology and effectiveness of (a) inhibition of the unaffected hemisphere, (b) facilitation of the affected hemisphere and (c) combined application of repetitive transcranial magnetic stimulation over the affected and unaffected hemispheres to treat impaired hand function after stroke are presented. Problems and limitations of repetitive transcranial magnetic stimulation in stroke rehabilitation are discussed and visions for future clinical research are presented.Fortschritte der Neurologie · Psychiatrie 03/2014; 82(3):135-44. DOI:10.1055/s-0034-1365926 · 0.85 Impact Factor
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ABSTRACT: Neuro-imaging studies have suggested that the ability to imitate meaningless and meaningful gestures may differentially depend on superior (SPL) and inferior (IPL) parietal lobule. Therefore, we hypothesized that imaging-guided neuro-navigated continuous theta burst stimulation (cTBS) over left SPL mainly affects meaningless and over left IPL predominantly meaningful gestures. Twelve healthy subjects participated in this study. High resolution structural MRI was used for imaging guided neuro-navigation cTBS. Participants were targeted with one train of cTBS in three experimental sessions: sham stimulation over vertex and real cTBS over left SPL and IPL, respectively. An imitation task, including 24 meaningless and 24 meaningful gestures, was performed 'offline'. cTBS over both left IPL and SPL significantly interfered with gestural imitation. There was no differential effect of SPL and IPL cTBS on gesture type (meaningless versus meaningful). Our findings confirm that left posterior parietal cortex plays a predominant role in gestural imitation. However, the hypothesis based on the dual route model suggesting a differential role of SPL and IPL in the processing of meaningless and meaningful gestures could not be confirmed. Left SPL and IPL play a common role within the posterior-parietal network in gestural imitation regardless of semantic content.Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 09/2013; 125(3). DOI:10.1016/j.clinph.2013.07.024 · 3.12 Impact Factor