Abstract
We report a novel subthreshold non-invasive brain stimulation approach that we refer to as kilohertz transcranial magnetic perturbation, or kTMP. kTMP is a magnetic induction method that delivers kHz-frequency cortical E-fields and, through amplitude modulation of the kHz carrier frequency, may mimic E-fields at physiological frequencies. To evaluate the efficacy of kTMP, we used suprathreshold TMS to elicit motor-evoked potentials (MEP) in a peripheral muscle, comparing the amplitude of the MEPs before and after kTMP stimulation. In Experiment 1, we used non-modulated kTMP with an E-field amplitude of 2 V/m over motor cortex. Ten minutes of kTMP stimulation resulted in an increase in cortical excitability in a frequency-specific manner. We replicated this effect in Experiment 2 and found that amplitude-modulation at 20 Hz produced an additional boost in cortical excitability. The only percept associated with kTMP is a faint auditory tone, making kTMP ideal for double-blind experimentation.
Competing Interest Statement
The authors declare the following competing interests: LL, CM, BI, RBI and DS have stock ownership in Magnetic Tides, a non-publicly traded company created to develop new methods of non-invasive brain stimulation. UC Berkley holds the patent rights related to the kTMP technology but has provided Magnetic Tides with an exclusive licensing agreement.
Footnotes
↵* co-first authors.