Exploring parameters of gamma transcranial alternating current stimulation (tACS) and full‐spectrum transcranial random noise stimulation (tRNS) on human pharyngeal cortical excitability. Issue 9 (3rd June 2021)

• Record Type: Journal Article
• Authors: Zhang, Mengqing; Cheng, Ivy; Sasegbon, Ayodele; Dou, Zulin; Hamdy, Shaheen
• Is Part Of: Neurogastroenterology & motility. Volume 33:Issue 9(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-06-03
• Subjects: gamma frequency -- pharyngeal cortical excitability -- swallowing -- transcranial alternating current stimulation -- transcranial random noise stimulation; Gastrointestinal system -- Motility -- Periodicals; Gastrointestinal system -- Innervation -- Periodicals; 616.33
• DOI: 10.1111/nmo.14173
• Languages: English
• ISSNs: 1350-1925

Abstract

Abstract: Background: Transcranial alternating current stimulation (tACS) and transcranial random noise stimulation (tRNS) have been shown to have physiological and functional effects on brain excitability and motor behavior. Yet, little is known about their effects in the swallowing system. Aim: To examine the effects and optimal stimulation parameters of tACS and tRNS for modulating excitability of human pharyngeal motor cortex. Methods: 10 Hz (alpha), 20 Hz (beta), 70 Hz (gamma) tACS, 0.1–640 Hz (full‐spectrum) tRNS, and sham were applied over pharyngeal motor cortices at 1.5 mA current intensity for 10 min in 15 healthy participants. Pharyngeal motor–evoked and thenar motor–evoked potentials (PMEPs and TMEPs) were assessed before and up to 2 h after stimulation with single‐pulse transcranial magnetic stimulation. Averaged MEP amplitude and latency changes were analyzed using repeated measures ANOVA (rmANOVA). Key Results: Two‐way rmANOVA across all active interventions demonstrated a significant MEP interaction both in the stimulated pharyngeal cortex (F (4, 56) = 1.731, p = 0.038) and in the ipsilateral thenar cortex (F (4, 56) = 1.506, p = 0.048). Compared to sham, subsequent post hoc tests showed site‐specific and sustained (60–120 min) increases in PMEPs with gamma tACS and tRNS ( p = 0.005, p = 0.027, respectively) and for TMEPs with beta tACS ( p = 0.006). Conclusions and Inferences: Our findings suggest that the effects of tACS and tRNS are frequency‐dependent and cortical (representation) site‐specific with both gamma tACS and full‐spectrum tRNS enhancing human pharyngeal cortical excitability. These techniques hold promise as potential treatments for neurological dysphagia. Abstract : Compared with sham, across time, both 70 Hz transcranial alternating current stimulation (tACS) and full‐spectrum transcranial random noise stimulation at 1.5 mA for 10 min produced increases in cortical excitability for the pharynx in the conditioned (stimulated) hemisphere (F[1, 14] = 9.065, * p = 0.005 and F[1, 14] = 5.394, * p = 0.027, respectively), with increases in pharyngeal motor evoked amplitudes of up to +77 ± 24% and +59 ± 30%, respectively. By contrast, 10 Hz tACS appeared to slightly suppress pharyngeal cortical excitability, with a trend to decreased pharyngeal motor evoked amplitudes of −30 ± 7% whereas 20Hz tACS elicited no obvious changes in pharyngeal amplitudes.