Transcranial temporal interference stimulation (TIS) is an emerging novel tool for non-invasive transcranial brain stimulation that holds the potential for focal and steerable neuromodulation, and the possibility to stimulate focally at depth. TIS involves combining two high frequency waveforms to create a waveform with a "beat" frequency that is physiological relevant for neuromodulation. Successful applications to deep brain targets as well as steerability of the stimulation focus have been demonstrated in mice. Numerous recent investigations in humans have shown great clinical potential for this technology, however several questions about the basic mechanism of TIS action remain. The investigators will apply TIS to the motor cortex of humans and use established transcranial magnetic stimulation techniques to assess cortical excitability in relation to the phase of the TIS waveform. Using TMS, the investigators will i) validate that effects of TIS are due to the "beat" frequency and not the high frequency carrier signal, ii) evaluate the effect of the TIS carrier frequency, and iii) evaluate that whether changes in corticospinal excitability outlast the period of stimulation. Knowledge gained from this experiment will provide a basis for the future use of TIS for clinical applications, including informing parameter optimization.
Free of neurological or orthopedic conditions that may impact the ability to participate.
Right-hand dominant (self-reported)
Aged 18-65 years
Ferromagnetic metal implants in the brain/skull or elsewhere (dental implants excluded).
Any implanted electronic device (e.g. cardiac pacemaker, cochlear implant, deep brain stimulator, medication infusion pump; vagal nerve stimulator)
Diseased or damaged skin on face or scalp
History of migraines, fainting, seizures/epilepsy, or psychiatric illness
Crossover
transcranial Temporal Interference Stimulation
DeviceWe will apply temporal interference stimulation (tTIS) for 20 minutes over the motor cortex concurrent with single-pulse transcranial magnetic stimulation (TMS) (also over the motor cortex). Motor evoked potentials will be recorded using electromyography (EMG).
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Treatment groupsSee each treatment group below.
Online phase-dependent modulation of corticospinal excitability using the relevance value (R.V.)
Explained variance (R2) of best-fit sinusoids will be multiplied by the variance of measured values to obtain the established "relevance value" (R.V.), to be used as our primary outcome. Relevance values assume phase-dependent modulation with a large amplitude is more meaningful than one with small amplitude and the same R2. Critically, phase-dependent responses to TIS represent direct evidence of modulation at beat frequency (fb).
Offline neuroplastic effects from pre to post
We define neuro- plastic effects as sustained modulation of excitability fol- lowing cessation of transcranial current sitmulation (tCS). Fifteen single-pulse MEPs will be acquired at the FDI hotspot prior to and at 0, 15 and 30 minutes after tCS (tpre, t0, t15, t30). Our primary outcome will be MEP amplitude change from tpre to t0.
Offline neuroplastic post effects
Retention of neuromodulation at t15 and t30.
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Northeastern University
Lead sponsor
National Institute of Neurological Disorders and Stroke (NINDS)
Collaborator
