Abstract
To examine the effects of intermittent TBS (iTBS) and continuous TBS (cTBS) on cortical reactivity in the dorsolateral prefrontal cortex. 10 healthy participants were stimulated with either iTBS, cTBS or sham at F3 electrode. Single- and paired-pulse TMS and concurrent electroencephalography (EEG) were used to assess change in cortical reactivity and long-interval intracortical inhibition (LICI) via TMS-evoked potentials (TEPs) and TMS-evoked oscillations. Significant increases in N120 amplitudes (p<0.01) were observed following iTBS over prefrontal cortex. Changes in TMS-evoked theta oscillations and LICI of theta oscillations were also observed following iTBS (increase) and cTBS (decrease). Change in LICI of theta oscillations correlated with change in N120 amplitude following TBS (r=-0.670, p=0.001). This study provides preliminary evidence that TBS produces direct changes in cortical reactivity in the prefrontal cortex. Combining TBS with TMS-EEG may be a useful approach to optimise stimulation paradigms prior to the conduct of clinical trials. TBS is able to modulate cortical reactivity and cortical inhibition in the prefrontal cortex.
Highlights
Repetitive transcranial magnetic stimulation is a non-invasive brain stimulation method capable of modulating the excitability of cortical circuits for extended periods of time and has been utilized in both research and clinical applications (Machado et al, 2013)
Change in long-interval intracortical inhibition (LICI) of theta oscillations correlated with change in N120 amplitude following Theta burst stimulation (TBS) (r = -0.670, p = 0.001)
Combining TBS with TMS-EEG may be a useful approach to optimise stimulation paradigms prior to the conduct of clinical trials
Summary
Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation method capable of modulating the excitability of cortical circuits for extended periods of time and has been utilized in both research and clinical applications (Machado et al , 2013). In particular, coupling of theta and gamma frequencies has been shown to play a key role in the communication between neuronal networks, as well as in synaptic plasticity to promote learning and memory (Fell et al , 2011, Machado et al , 2013, Colgin, 2015, Lega et al , 2016) As such, this phase-locked firing pattern of stimulation appears to have effects on cortical excitability that are the equivalent, if not greater than those produced with traditional rTMS methods, and there is some evidence of longer-lasting aftereffect duration (Nyffeler et al , 2006, Yang et al , 2015). Establishing that changes in cortical excitability due to TBS can be detected with TMS-EEG will allow the use of these approaches in preclinical studies investigating the optimal methods to induce changes in cortical activity
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