Depression of motor cortex excitability by low‐frequency transcranial magnetic stimulation

Abstract

We studied the effects of low-frequency transcranial magnetic stimulation (TMS) on motor cortex excitability in humans. TMS at 0.1 Hz for 1 hour did not change cortical excitability. Stimulation at 0.9 Hz for 15 minutes (810 pulses), similar to the parameters used to induce long-term depression (LTD) in cortical slice preparations and in vivo animal studies, led to a mean decrease in motor evoked potential (MEP) amplitude of 19.5%. The decrease in cortical excitability lasted for at least 15 minutes after the end of the 0.9 Hz stimulation. The mechanism underlying this decrease in excitability may be similar to LTD. TMS-induced reduction of cortical excitability has potential clinical applications in diseases such as epilepsy and myoclonus. Spread of excitation, which may be a warning sign for seizures, occurred in one subject and was not accompanied by increased MEP amplitude, suggesting that spread of excitation and amplitude changes are different phenomena and also indicating the need for adequate monitoring even with stimulations at low frequencies.

Effects of tDCS on motor learning and memory formation: A consensus and critical position paper

“…Present problems in the field include: (1) insufficient use of double-blind designs (see above, for example only 25 out of the 60 published studies on tDCS effects on motor learning in healthy adults reviewed here utilized double-blind designs) and positive controls (stimulation of other cortical regions); (2) insufficient differentiation and understanding of design and claims when carrying out exploratory (hypothesis-generating) versus confirmatory (hypothesis-driven) research (the former suggesting trends and providing data for prospective power analysis and the latter, strengthened by preregistration (Finkel, Eastwick, & Reis, 2015), allowing drawing conclusions on particular effects; (3) insufficient efforts to reduce false-positive rates in studies geared to provide proof of principle data to power subsequent clinical trials; (4) scarcity of preregistration of hypothesis, design, power analysis and data processing for research written up as hypothesis-driven and confirmatory (see for example https://blogs.royalsociety.org/publishing/registered-reports/); (5) insufficient prepublication and sharing of materials (Lauer, Krumholz, & Topol, 2015;Morey et al, 2016), particularly in relation to negative results; (6) insufficient post-publication repositories of data (see for example (Campbell et al, 2002)) and in general (Nosek et al, 2015)) to allow additional analyses; (7) seldom use of experimental designs with replications built in (Anderson et al, 2016;Cohen et al, 1997;Gilbert, King, Pettigrew, & Wilson, 2016;Nosek et al, 2015); and (8) use of appropriate sample size based on prospective power analysis for studies claimed to be hypothesis-driven.…”

“…It has been argued that rTMS and tDCS can either enhance or decrease excitability in targeted cortical regions depending on the parameters of stimulation employed (Chen et al, 1997;Galea, Jayaram, Ajagbe, & Celnik, 2009;Labruna et al, 2016;Woods et al, 2016) and the underlying intrinsic state of the stimulated brain networks (Dayan, Censor, Buch, Sandrini, & Cohen, 2013;Sandrini, Umilta, & Rusconi, 2011). tDCS has also been used as a tool to gain insight into brain-behavior interactions and to explore possible causal relationships between altered activity in relatively large regions of the brain and particular behaviors .…”

Dorsolateral prefrontal cortex, working memory and episodic memory processes: insight through transcranial magnetic stimulation techniques

“…At the beginning, TMS was almost exclusively applied to spinal roots, and cranial and peripheral nerves [15] .…”

Brain Stimulation Techniques in the Treatment of Obsessive-Compulsive Disorder: Current and Future Directions

“…TMS protocols are generally divided into two types of procedures according to the frequency used: low-frequency TMS (<1 Hz) and highfrequency TMS ( < 20 Hz). Depending on stimulation parameters (frequency, rate, and duration), repetitive stimuli to specific cortical regions can either decrease or enhance the excitability of the affected brain structures (ie, cerebral cortex [15][16][17] ) and modify regional cerebral blood flow. 18,19 …”