The effects of low- and high-frequency repetitive TMS on the input/output properties of the human corticospinal pathway

Abstract

The objective of this study was to characterize the effects of various parameters (notably the frequency and intensity) of repetitive transcranial magnetic stimulation (rTMS) applied over the primary motor (M1) and premotor (PMC) cortices on the excitability of the first dorsalis interosseus (FDI) corticospinal pathway. To this end, we applied a comprehensive input-output analysis after fitting the experimental results to a sigmoidal function. Twenty-six healthy subjects participated in the experiments. Repetitive TMS was applied either over M1 or PMC at 1 Hz (LF) for 30 min (1,800 pulses) or at 20 Hz (HF) for 20 min (1,600 pulses). In the HF condition, the TMS intensity was set to 90% (HF(90)) of the FDI's resting motor threshold (RMT). In the LF condition, the TMS intensity was set to either 90% (LF(90)) or 115% (LF(115)) of the RMT. The FDI input/output (I/O) curve was measured on both sides of the body before rTMS (the Pre session) and then during two Post sessions. For each subject, the I/O curves (i.e., the integral of the FDI motor-evoked potential (MEP) vs. stimulus intensity) were fitted using a Boltzmann sigmoidal function. The graph's maximum slope, S (50) and plateau value were then compared between Pre and Post sessions. LF(115) over M1 increased the slope of the FDI I/O curve but did not change the S (50) and plateau value. This also suggested an increase in the RMT. HF(90) led to a more complex effect, with an increase in the slope and a decrease in the S (50) and plateau value. We did not see a cross effect on the homologous FDI corticospinal pathway, and only PMC LF(90) had an effect on ipsilateral corticospinal excitability. Our results suggest that rTMS may exert a more complex influence on cortical network excitability than is usually reported (i.e. simple inhibitory or facilitatory effects). Analysis of the fitted stimulus response curve indicates a dichotomous influence of both low- and high-frequency rTMS on M1 cortical excitability; this may reflect intermingled effects on excitatory and inhibitory cortical networks.

Efficacy and time course of paired associative stimulation in cortical plasticity: Implications for neuropsychiatry

“…In addition, PAS LTP appears to result in larger changes in cortical excitability as compared to PAS LTD suggesting a difference in physiological susceptibility favouring PAS LTP . Weaker cortical depression as compared to cortical potentiation is consistent with findings of other stimulation techniques like repetitive TMS (Pascual-Leone et al, 1994;Maeda et al, 2000;Gorsler et al, 2003;Houdayer et al, 2008) and theta-burst stimulation (Huang et al, 2005;Di Lazzaro et al, 2011;Brownjohn et al, 2014;Wischnewski and Schutter, 2015). Also, the difference between PAS LTP and PAS LTD is compatible with both in vitro and in vivo animal studies (Yang et al, 1999;Froemke and Dan, 2002).…”

Cognitive Impairment After Sleep Deprivation Rescued by Transcranial Magnetic Stimulation Application in Octodon degus

“…For instance, TMS has shown to evoke a diversity of different responses depending on the stimulated site or intensity (Rizzo et al, 2004) (Yang et al, 2012) (Houdayer et al, 2008). We might not rule out that probably appreciable modifications can take place in nervous system during the exposure time, but nevertheless ultimately leading to a more efficient transmission of neural signals, tolerating greater capacity to moderate the cognitive dysfunction induced by SD, as shown by the BM and RAM approaches (Figs.…”

Long-Term Effects of Repetitive Transcranial Magnetic Stimulation on Markers for Neuroplasticity: Differential Outcomes in Anesthetized and Awake Animals

“…It is important to mention that such stimulation differs not only in its frequency but also in the overall pattern (intermittent vs continuous; see Materials and Methods), and this may also play a role in the differential lasting outcomes on markers for neuroplasticity, especially given that different stimulation frequencies can result in differential activation of immediate early genes in the rat brain (AydinAbidin et al, 2008). While low-frequency electrical stimulation generally leads to LTD-like effects (Hoffman and Cavus, 2002;Houdayer et al, 2008), the induction of this form of plasticity modulation in vivo has always proved a greater challenge (Errington et al, 1995;Abraham et al, 1996). The responses to lowfrequency stimulation are generally more variable, and the aftereffect durations are shorter (Gangitano et al, 2002;Fitzgerald et al, 2006).…”

“…Changes in TMS frequency and stimulation patterns can result in varying long-term effects. High-frequency stimulation (Ͼ3 Hz) generally results in facilitation-an effect that shares similarities with long-term potentiation (LTP), while low-frequency rTMS (Յ1 Hz) induces reduction of synaptic efficiency-an effect that shares similarities with long-term depression (LTD) (Huang et al, 2005;Houdayer et al, 2008). Nevertheless, little is known about the long-lasting neurochemical and physiological effects of rTMS, because most neurobiological studies have focused on the immediate effects induced after the stimulation.…”