View clinical trials related to Cortical Excitability.
Filter by:To assess the effect of continuous (cTBS) and intermittent theta burst stimulation (iTBS) stimulation on motor cortex excitability using TMS-EEG. Based on prior literature, the investigators hypothesized that N100 amplitude would be differently modulated by these two modalities.
Major depressive disorder (MDD) is a serious mental illness and the leading cause of disability worldwide. New pharmacotherapeutic agents with complementary neurobiological mechanism and better side effect profile are of great needs. In addition to the monoamine system, the glutamatergic system plays a crucial role in MDD. L-theanine (N5-ethyl-L-glutamine) is the primary psychoactive component uniquely in green tea. Preclinical studies have demonstrated anti-depressant effect of L-theanine in rodents and provided evidences for its pharmacological properties of N-methyl-D-aspartate (NMDA) and gamma-aminobutyric acid (GABA) agonism. Yet these effects have not been proven in humans. Only one open-label clinical trial has studied and supported antidepressant effects of L-theanine in MDD patients. We propose using pair-pulse transcranial magnetic stimulation (ppTMS) to probe how L-theanine may manipulate the glutamatergic and GABA systems in the frontal region by changing cortical excitability first in healthy subjects. We plan to investigate the neurobiological effects of L-theanine in healthy subjects first. Granted that the first phase pilot trial provides neurophysiological evidence of L-theanine on motor cortex excitability in human subjects, next phases of studies on L-theanine in MDD patients cortical excitability could be justified.
Caffeine is a psychostimulant drug. It acts as a competitive antagonist at adenosine receptors, which modulate cortical excitability as well. In deep brain stimulation (DBS), the production of adenosine following the release of adenosine triphosphate (ATP) explains the reduction of tremor. Binding of adenosine to adenosine A1 receptors suppresses excitatory transmission in the thalamus and hereby reduces both tremor-and DBS-induced side effects. Also, the effect of adenosine was attenuated following the administration of the 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX) adenosine A1 receptor antagonist. Therefore, the presence of a receptor antagonist such as caffeine was suggested to reduce the effectiveness of deep brain stimulation (DBS) in treating tremor and other movement disorders. Based on this finding, the investigators hypothesize that the antagonistic effect of caffeine can tentatively block the excitatory effects of transcranial alternating current stimulation (tACS). The plasticity effects might differ among caffeine users and non- caffeine users depending on the availability of receptor binding sites. Apart from that, a major issue in NIBS studies including those studying motor-evoked potentials is the response variability both within and between individuals. The trial to trial variability of motor evoked potentials (MEPs) may be affected by many factors. Inherent to caffeine is its effect on vigilance. In this study, the investigator shall monitor the participant's vigilance by pupillometry to (1) better understand the factors, which might cause variability in transcranial excitability induction studies and (2) to separate the direct pharmacological effect from the indirect attentional effect of caffeine.
Caffeine is a widely used psychostimulant drug and acts as a competitive antagonist at adenosine receptors. Its effect is on neurons and glial cells of all brain areas. Chronic consumption of caffeine leads to tolerance which might be associated with an increased number of binding sites in the brain. In deep brain stimulation (DBS), the production of adenosine following the release of adenosine triphosphate (ATP) explains the reduction of in tremor. Binding of adenosine to adenosine A1 receptor suppresses excitatory transmission in the thalamus and thus reduces both tremor-and DBS-induced side effects. Also, the effect of adenosine was attenuated following the administration of the 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX) adenosine A1 receptor antagonist. Therefore, the presence of a receptor antagonist such as caffeine was suggested to reduce the effectiveness of deep brain stimulation (DBS) in treating tremor and other movement disorders. In light with this finding, we anticipate that the antagonistic effect of caffeine is a culprit to the reduction of effectiveness of any stimulation protocol in non-invasive stimulation (NIBS). In particular the excitatory effects of a NIBS protocol can tentatively be blocked in the presence of caffeine. In this study, the effects of caffeine consumption on cortical excitability at the sensorimotor cortex shall be examined on focal and non-focal plasticity. Focal plasticity will be induced by paired associated stimulation (PAS) and global cortical plasticity from transcranial alternating current (tACS) stimulation. In case of tACS stimulation, 1) an excitatory protocol (tACS, 140 Hz, 1 mA) and 2) an inhibitory protocol (tACS, 140 Hz, 0.4 mA) with the active electrode over M1 and the return electrode over the orbitofrontal cortex will be used. Changes in cortical excitability are assessed using transcranial magnetic stimulation (TMS) recordings. Research goals are to examine the effects of caffeine consumption on sensorimotor cortical excitability and stimulation induced plasticity. In addition, this study explores further factors which usually contribute to variability in cortical excitability studies. The results are expected to give a useful recommendation for researchers to reduce confounding factors and hereby improves repeatability.
Healthy individuals, after reading and signing the free and informed consent will be submitted to a single session to obtain the normal neurophysiological measures and thus compare with those obtained in individuals with PD. Healthy and post stroke patients will be submitted to a neurophysiological evaluation through transcranial magnetic stimulation (TMS) and electroencephalography (EEG). The post stroke patients will also performed the evaluation trought the fugl meyer scale.
This study has two main goals : - to develop the cortcial excitbality (CE) measurement methodology using coupling between transcranial magnetic stimulation (TMS) and physiological recordings such as electroencephalography (EEG) and electromyography (EMG), - to automatize these measurements using robotized TMS. Assessing CE is a preliminary and crucial step in any TMS protocol, in either fundamental or clinical research. It is an important indicator which determine the stimulation power applied on the cortical target during the TMS experiment, or during the rTMS cure (patients). CE is in general measured on the motor cortex using EMG activity as the main indicator of the system's response, whatever the real cortical target is located. The present study thus propose to generalize this measurement on other cortical areas in link with the actual targets, and using other external recordings such as EEG. Moreover, as neuronavigation systems significantly improved TMS precision in the past years, CE measurements could significantly gain to become fully automatized using robotized TMS.
In this study the effect of tDCS intensity on motor performance and corticospinal (CS) excitability is evaluated. The investigators expect that a positive relationship between current intensity and motor performance/CS excitability.