Abstracts

Rationale: The incidence of epilepsy in the US alone is 1 in 26. Transcranial focal electrical stimulation (TFS: 300 Hz biphasic pulses, 1-2 min) via tripolar concentric ring electrodes (TCREs) have demonstrated: reduced or abolished electrographic and behavioral activities of induced seizures and status epilepticus in three rat models (pilocarpine, PTZ, penicillin, (Besio, 2013)); prevention of electrical amygdaloid kindling in naïve cat brains (Valds-Cruz, 2016); pain blocking (Besio, 2016); and prevention of glutamate release (Santana-Gómez, 2015). TFS in rats did not cause skin damage or affect memory (Rogel-Salazar, 2013). Here, we report the initial, and encouraging, safety results of applying TFS in healthy humans. Methods: TFS safety is being tested on participant’s skin and behavior during three sessions (S1, S2, S3) approximately 1-week apart. At S1, participants rate each step of the electrode application process on the arm and scalp for pain (0-10, none to worst) and the experimenter rates skin erythema (Draize scale, 0-4; no change-beet red, Guartienti, 2014) (NuPrep cleansing gel; Ten20 EEG paste; gel + paste; gel + paste + TCRE; gel + paste + TCRE + TFS or sham (SH) for 2 mins). Baseline (BL) performance on a working memory task (WMT: 5-min each of 2-back and 3-back) is recorded before scalp TFS or SH while 16 channels of EEG are collected at 512 Hz (t-Interface 20, g.USB amplifier and BCI2000) over the left prefrontal cortex (8 TCRE signals (tEEG), and 8 emulated EEG (eEEG, Makeyev, 2013)). TFS or SH is applied at F3. At S2 they perform a BL WMT, TFS or SH is delivered, then, they perform the WMT at 3 post-intervention time points (in mins: T0, T20 and T40). At S3, they perform the WMT at the 3 time points. Results: Ten healthy participants have completed the study (6 male, mean age = 32, 6 SH, 4 TFS). All participants reported one (1) for pain (arm: 1 gel, 1 paste; scalp: 1 each for the last 3 scalp steps, 1 at SH at S2) and erythema (four Draize one (1) for NuPrep step: 3 at AF3, 1 arm). There is no significant difference between the TFS and SH groups (Wilcoxon rank-sum) in accuracy or reaction time (RT) of the WMT at the 3 BLs and 3 S2 and S3 timepoints (9 block accuracy (mean ± SD): SH, 86.1 ± 0.11, range 62-100; TFS: 81.6 ± 0.12, range 55-96; mean RTs: SH, 394ms ± 106 SD, range 201-650; TFS: 445ms ± 155, range 280-699).  WMT accuracy and RT change from S2 to S3 between groups are not significantly different. Within subject t-tests of accuracy and from S2 and S3 are not significant. Significant differences (Wilcoxon rank sum) in tEEG amplitude at F3 (unfiltered, 3-40Hz) between TFS and SH were found for BL2 and S3 T0 (p<0.05).  Conclusions: These preliminary results indicate TFS is safe in humans. Further study will determine if TFS has beneficial effects in persons with neurological disorders. ReferencesBesio et al. TFS potentiates diazepam. Epilep & Behav. 2013;28:432-436.Valdés-Cruz A et al. Poster 407.16. TFS antiepileptogenic effects, Proc. SfN 2016, San Diego CA, USA.Besio et al. Poster 145.06. TFS induced analgesic effects, Proc. SfN 2016, San Diego CA, USA.Santana-Gómez et al. TFS reduces the convulsive. Epilep & Behav. 2015;49:33-39.Rogel-Salazar et al. Transcranial focal electrical stimulation. Epilep & Behav. 2013;27:154-158.Makeyev O et al. Emulating conventional disc electrode, IEEE SPMBS, NYC, 1-4, 2013. Funding: NSF awards 1539068 and 1701049 and NIH Grant P41EB018783 (NIBIB)