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Comparing amplitudes of transcranial direct current stimulation (tDCS) to the sensorimotor cortex during swallowing

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Abstract

Purpose

Transcranial direct current stimulation (tDCS) can alter cortical excitability, making it a useful tool for promoting neuroplasticity in dysphagia rehabilitation. Clinical trials show functional improvements in swallowing following anodal tDCS despite varying dosing parameters and outcomes. The aim of the current study was to determine the most effective amplitude criterion (e.g., 0 mA [sham/control], 1 mA, 2 mA) of anodal tDCS for upregulating the swallowing sensorimotor cortex.

Method

As a novel paradigm, tDCS, functional near-infrared spectroscopy (fNIRS), and surface electromyography (sEMG) were simultaneously administered while participants completed a swallowing task. This allowed for measurement of the cortical hemodynamic response and submental muscle contraction before, during, and after tDCS. At the conclusion of the study, participants were asked to rate their level of discomfort associated with tDCS using a visual analog scale.

Results

There was no significant difference in the hemodynamic response by time or amplitude. However, post-hoc analyses indicated that in the post-stimulation period, changes to the hemodynamic response in the left (stimulated) hemisphere were significantly different for the groups receiving 1 mA and 2 mA of tDCS compared to baseline. Participants receiving 1 mA of tDCS demonstrated reduced hemodynamic response. There was no significant difference in submental muscle contraction during or after tDCS regardless of amplitude. Anodal tDCS was well tolerated in healthy adults with no difference among participant discomfort scores across tDCS amplitude.

Conclusions

During a swallowing task, healthy volunteers receiving 1 mA of anodal tDCS demonstrated a suppressed hemodynamic response during and after stimulation whereas those receiving 2 mA of anodal tDCS had an increase in the hemodynamic response. tDCS remains a promising tool in dysphagia rehabilitation, but dosing parameters require further clarification.

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Data availability

Due to the nature of this research, participants of this study did not agree for their data to be shared publicly, so supporting data is not available.

Code availability

NA.

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Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. James Madison University supported participant incentives in the form of gift cards through internal funding mechanisms.

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Authors and Affiliations

  1. School of Communication, Communication Sciences and Disorders, Emerson College, 120 Boylston St., Boston, MA, 02116, USA

    Lindsay Griffin

  2. College of Health and Behavioral Studies, Communication Sciences and Disorders, James Madison University, 235 Martin Luther King Jr. Way, Harrisonburg, VA, 22807, USA

    Lindsay Griffin, Erin Kamarunas, Christina Kuo & Cynthia O’Donoghue

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  1. Lindsay Griffin
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  2. Erin Kamarunas
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  3. Christina Kuo
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  4. Cynthia O’Donoghue
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Contributions

All authors contributed to the study’s conception and design. Material preparation and data collection were performed by LG and EK. Data analysis was completed by LG and EK. The first draft of the manuscript was written by LG and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Lindsay Griffin.

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Conflict of interest

Lindsay Griffin: None known. Erin Kamarunas: None known. Christina Kuo: None known. Cynthia O’Donoghue: None known.

Ethics approval

This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Internal Review Board of James Madison University (March 2018, No. 18–0423).

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The authors affirm that all study participants provided informed written consent prior to study enrollment.

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The authors affirm that all study participants provided informed consent for publication.

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Communicated by Melvyn A. Goodale.

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Griffin, L., Kamarunas, E., Kuo, C. et al. Comparing amplitudes of transcranial direct current stimulation (tDCS) to the sensorimotor cortex during swallowing. Exp Brain Res 240, 1811–1822 (2022). https://doi.org/10.1007/s00221-022-06381-z

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  • DOI: https://doi.org/10.1007/s00221-022-06381-z

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