Modulation of Motor Function by Stimulation of the Central and Peripheral Nervous System

Plain-language summary

Objectives Noninvasive stimulation of the central and peripheral nervous system, including transcranial magnetic stimulation (TMS), transcranial direct and alternating current stimulation (tDCS and tACS, respectively) and cutaneous/peripheral nerve stimulation (C/PNS) alone or paired with TMS (paired associative stimulation, PAS), has been increasingly used in the investigation of cortical plasticity and as a possible adjuvant strategy in neurorehabilitation. It has been shown that TMS, tDCS, tACS and C/PNS can modulate motor function in healthy volunteers, as well as in patients with neurological disorders such as stroke. One fundamental problem is that the optimal parameters of stimulation to modulate motor function by all of these techniques are not known. The purpose of this protocol is to explore within safe guidelines, the effects of different stimulation parameters on motor cortical function, on oscillatory brain dynamics measured with magnetoencephalography (MEG) and electroencephalography (EEG), on eye movements, and on fMRI activation. In addition, this protocol will be used to train new fellows coming to NINDS Human Cortical Physiology Section (HCPS) in the use of TMS, tDCS, tACS and C/PNS techniques. We expect that information emerging from these studies will allow us to 1) optimize experimental protocols or stimulation parameters to collect pilot data in healthy volunteer for future patient-oriented hypothesis-driven protocols,2)to collect pilot data for power analysis for future patient-oriented hypothesis driven protocols, and 3) to train new fellows in the use of these different methods. Study Population Up to 1500 healthy volunteers, age 18 and older. Design Healthy volunteers will receive one or more of the following types of stimulation alone or in combination: (1) single- and paired-pulse TMS with inter-stimulus intervals of greater than 1s and up to 20s and intensities of up to 100% of stimulator output; (2) 1 Hz TMS for up to 30mins and up to 115% of resting motor threshold (RMT) intensity; (3) tDCS applied at an intensity of up to 4 mA for a duration of up to 60mins, as long the total charge does not exceed 7.2 C; (4) tACS applied at a peak-to-peak intensity of up to 4 mA for a duration of up to 60 minutes, minutes, as long the total charge does not exceed 7.2 C; (5) C/PNS applied alone with intensities below 130% of the peripherally-elicited-motor-threshold for up to 2 hours, or intensities up to 300% of sensory threshold when C/PNS is paired with TMS. All of these parameters of stimulation and procedures have safely been used as previously reported in the literature. Sham stimulations will be delivered for each modality as scientifically needed. Some substudies may involve recording of behavior or brain activity only (such as behavioral testing, MRI, and MEG) if brain stimulation targets are unknown. This information can help design future brain stimulation protocols. Each subject may participate in up to 20 sessions. A single session may last no longer than 8 hours to allow for initial testing paradigm followed by retests or performing other components of the same substudy later in the day. Appropriate rest breaks and meal breaks will occur during long sessions. Subjects participate in one experimental session per day under this protocol. The 20 experimental sessions will be scheduled over a twenty-year period. CTDB is used to track the number of sessions per subject so it does not exceed 20 sessions. The AIs are responsible for entering the subjects/sessions into CTDB. We will test the effects of these different forms of stimulation on motor cortical excitability, cognitive and motor behavioral tasks, and brain state measures derived from neuroimaging data (i.e. - MRI, fMRI, MEG and EEG). Stimulation may be applied before, after, or during physiological (i.e. motor evoked potentials, M-wave, F-wave, or H-Reflexes), neuroimaging or behavioral measures. Under this protocol, we conduct: Exploratory Sub-studies: These substudies are exploratory in nature and are conducted in order to develop information to generate better informed future hypotheses and/or power analyses. We have set an upper limit of 40 subjects per sub-study. Hypothesis-Testing Sub-studies: Hypothesis-testing sub-studies are studies with specific hypotheses to be tested. These sub-studies undergo statistical and PIRC review after 6 subjects per group (e.g., after 12 subjects, 6 per arm, if two groups are studied), before additional subjects can be recruited. Together, the P.I. and PIRC will decide whether to continue the sub-study with more subjects without an amendment or whether an amendment or protocol would be necessary. A memo requesting a review of hypothesis-testing sub-studies for possible additional enrollment (beyond 6) will be sent to PIRC and the statistical reviewer. This protocol is ......

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