tACS and tRNS Studies on Brain Control of Swallowing

Characterizing the Application of Transcranial Alternating Current Stimulation and Transcranial Random Noise Stimulation Over Human Pharyngeal Motor Cortex

Transcranial alternating current stimulation (tACS) and transcranial random noise stimulation (tRNS) are two (CE marked medical devices) new, non-invasive (over the scalp) brain stimulation (NIBS) techniques. Both tACS and tRNS deliver a weak current continuously across the brain using pads placed over the scalp, which has been shown safe and well-tolerated by healthy adults and patients. These two techniques are able to softly alter physiological function within the brain. tACS can influence the brainwaves which have been demonstrated to play important roles in movement, sensation, and thinking functions. tACS and tRNS have been investigated for several years and have been shown to be safe, well tolerated and produce beneficial results in hand movement, hearing, and working memory. Swallowing problems are life-threatening symptom among patients with brain impairments and elderly people. Until now, there are no studies investigating whether tACS and tRNS can have a beneficial effect on swallowing function in human. Our aim is to examine the effects of different strengths of tACS and tRNS to determine the best approach for brain stimulation that controls swallowing action, before using these techniques in patients with (neurological) swallowing disorders. Participants: Healthy adults who are aged 18 years old or above with no medical complications or significant past medical history will be recruited in the study.

transcranial alternating current stimulation, transcranial random noise stimulation, frequency, full spectrum

All people studied will have each of the five treatments separately over different days in random order.

Stimulation will be applied at 10 Hz tACS with an intensity of 1.5 mA (peak to peak), a fade in/out of 10 s and a duration of 10min. 10 Hz tACS will be performed over the pharyngeal cortex region and contralateral supraorbital region.

Stimulation will be applied at 20 Hz tACS with an intensity of 1.5 mA (peak to peak), a fade in/out of 10 s and a duration of 10min. 20 Hz tACS will be performed over the pharyngeal cortex region and contralateral supraorbital region.

Stimulation will be applied at 70 Hz tACS with an intensity of 1.5 mA (peak to peak), a fade in/out of 10 s and a duration of 10min. 70 Hz tACS will be performed over the pharyngeal cortex region and contralateral supraorbital region.

Stimulation will be applied at 0.1-640Hz tRNS with an intensity of 1.5 mA (peak to peak), a fade in/out of 10 s and a duration of 10min. 0.1-640Hz tRNS will be performed over the pharyngeal cortex region and contralateral supraorbital region.

Stimulation will be performed only for 10 s before the fade out, with 20 Hz tACS and an intensity of 1.5 mA (peak to peak). Sham condition will be applied over pseudo-stimulation of pharyngeal cortex region and contralateral supraorbital region.

Transcranial alternating current stimulation (tACS) and transcranial random noise stimulation (tRNS) are two (CE marked medical devices) new, non-invasive (over the scalp) brain stimulation (NIBS) techniques. Both tACS and tRNS deliver a weak current continuously across the brain using pads placed over the scalp, which has been shown safe and well-tolerated by healthy adults and patients. These two techniques are able to softly alter physiological function within the brain. tACS can influence the brainwaves which have been demonstrated to play important roles in movement, sensation, and thinking functions. tACS and tRNS have been investigated for several years and have been shown to be safe, well tolerated and produce beneficial results in hand movement, hearing, and working memory.

Cortical excitability of the pharyngeal motor cortices are being assessed as the primary endpoints. Therefore, the changes in EMG pharyngeal motor evoked potential amplitudes (PMEPs) following the intervention applied to pharyngeal motor cortex are being collected.

These cortical excitability measurements will be recorded at baseline, followed by immediately after intervention, then every 15 minutes up to 120 minutes afterwards.

Inclusion Criteria: Healthy adults who are aged 18 years old or above with no medical complications or significant past medical history Exclusion Criteria: a history of epilepsy cardiac pacemaker previous brain surgery previous swallowing problems risk of potential pregnancy metal in the head or eyes use of medication that acts on the central nervous system.

The Gastrointestinal Sciences research team at the University of Manchester will have access to participants' identifiable information, but it will be anonymized as soon as participants are enrolled in this study. Representatives from the University of Manchester and regulatory authorities will have access to the anonymised data if required for auditing and monitoring process. However, participants' anonymised consent form, contact details, and data collected for this study will be retained for 5 years.

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