Springer Nature is making SARS-CoV-2 and COVID-19 research free. View research | View latest news | Sign up for updates

Guide to Enhancing Swallowing Initiation: Insights from Findings in Healthy Subjects and Dysphagic Patients

  • 788 Accesses

  • 2 Citations


Purpose of Review

Difficulty in initiating swallowing is one of the main symptoms of oropharyngeal dysphagia. Therefore, enhancing swallowing initiation is an important approach for the treatment of oropharyngeal dysphagia. This review aims to introduce recent approaches to enhancing swallowing and to discuss their therapeutic potential.

Recent Findings

Both central interventions such as non-invasive brain stimulation and peripheral interventions such as electrical stimulation to peripheral tissues are conducted to enhance swallowing. Recent studies have paid more attention to generating neuroplasticity to produce long-lasting facilitative effect on swallowing.


Transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), pharyngeal electrical stimulation (PES), transcutaneous electrical stimulation, and somatic and chemical stimulation were introduced. Considerable evidence supports the therapeutic potential of TMS and PES. Other approaches need further studies to verify their efficacy (e.g., duration of the effect and a limit of effectiveness) and/or possible risk of adverse effects.

This is a preview of subscription content, log in to check access.


Papers of particular interest, published recently, have been highlighted as: • Of importance

  1. 1.

    Ertekin C, Aydogdu I. Neurophysiology of swallowing. Clin Neurophysiol. 2003;114:2226–44.

  2. 2.

    Miller AJ. Deglutition. Physiol Rev. 1982;62:129–84.

  3. 3.

    Jean A. Brain steam control of swallowing: neuronal network and cellular mechanisms. Physiol Rev. 2001;81:929–69.

  4. 4.

    Sugiyama Y, Shiba K, Nakazawa K, Suzuki T, Umezaki T, Ezure K, et al. Axonal projections of medullary swallowing neurons in Guinea pigs. J Comp Neurol. 2011;519(11):2193–211.

  5. 5.

    Sumi T. Some properties of cortically-evoked swallowing and chewing in rabbits. Brain Res. 1969;15(1):107–20.

  6. 6.

    Weerasuriya A, Bieger D, Hockman CH. Basal forebrain facilitation of reflex swallowing in the cat. Brain Res. 1979;174(1):119–33.

  7. 7.

    Martin RE, Kemppainen P, Masuda Y, Yao D, Murray GM, Sessle BJ. Features of cortically evoked swallowing in the awake primate (Macaca fascicularis). J Neurophysiol. 1999;82(3):1529–41.

  8. 8.

    Martin RE, MacIntosh BJ, Smith RC, Barr AM, Stevens TK, Gati JS, et al. Cerebral areas processing swallowing and tongue movement are overlapping but distinct: a functional magnetic resonance imaging study. J Neurophysiol. 2004;92:2428–43.

  9. 9.

    Michou E, Hamdy S. Cortical input in control of swallowing. Curr Opin Otolaryngol Head Neck Surg. 2009;17:166–71.

  10. 10.

    Mihai PG, Otto M, Platz T, Eickhoff SB, Lotze M. Sequential evolution of cortical activity and effective connectivity of swallowing using fMRI. Hum Brain Mapp. 2014;35(12):5962–73.

  11. 11.

    Narita N, Yamamura K, Yao D, Martin RE, Sessle BJ. Effects of functional disruption of lateral pericentral cerebral cortex on primate swallowing. Brain Res. 1999;824(1):140–5.

  12. 12.

    Daniels SK, Foundas AL, Iglesia GC, Sullivan MA. Lesion site in unilateral stroke patients with dysphagia. J Stroke Cerebrovasc Dis. 1996;6:30–4.

  13. 13.

    Broadley S, Croser D, Cottrell J, Creevy M, Teo E, Yiu D, et al. Predictors of prolonged dysphagia following acute stroke. J Clin Neurosci. 2003;10(3):300–5.

  14. 14.

    Valdez DT, Salapatek A, Niznik G, et al. Swallowing and upper esophageal sphincter contraction with transcranialmagnetic-induced electrical stimulation. Am J Phys. 1993;264(2 Pt 1):G213–9.

  15. 15.

    • Simons A, Hamdy S. The use of brain stimulation in dysphagia management. Dysphagia. 2017;32:209–15. This is a review article explaining mechanisms of tDCS and rTMS and introducing published studies conducted in healthy subjects and dyspasic patients with the comparison of their therapeutic potentials.

  16. 16.

    Hamdy S, Aziz Q, Rothwell JC, Singh KD, Barlow J, Hughes DG, et al. The cortical topography of human swallowing musculature in health and disease. Nat Med. 1996;2(11):1217–24.

  17. 17.

    Hamdy S, Aziz Q, Rothwell JC, Crone R, Hughes D, Tallis RC, et al. Explaining oropharyngeal dysphagia after unilateral hemispheric stroke. Lancet. 1997;350(9079):686–92.

  18. 18.

    Hamdy S, Aziz Q, Rothwell JC, Power M, Singh KD, Nicholson DA, et al. Recovery of swallowing after dysphagic stroke relates to functional reorganization in the intact motor cortex. Gastroenterology. 1998;115(5):1104–12.

  19. 19.

    Mistry S, Verin E, Singh S, Jefferson S, Rothwell JC, Thompson DG, et al. Unilateral suppression of pharyngeal motor cortex to repetitive transcranial magnetic stimulation reveals functional asymmetry in the hemispheric projections to human swallowing. J Physiol. 2007;585(Pt 2):525–38.

  20. 20.

    Jefferson S, Mistry S, Michou E, Singh S, Rothwell JC, Hamdy S. Reversal of a virtual lesion in human pharyngeal motor cortex by high frequency contralesional brain stimulation. Gastroenterology. 2009;137(3):841–9.

  21. 21.

    Yang SN, Pyun SB, Kim HJ, Ahn HS, Rhyu BJ. Effectiveness of non-invasive brain stimulation in dysphagia subsequent to stroke: a systemic review and meta-analysis. Dysphagia. 2015;30(4):383–91.

  22. 22.

    • Michou E, Raginis-Zborowska A, Watanabe M, Lodhi T, Hamdy S. Repetitive transcranial magnetic stimulation: a novel approach for treating oropharyngeal dysphagia. Curr Gastroenterol Rep. 2016;18(2):10. This is a comprehensive review article explaining underlying neural mechanisms of the effects induced by rTMS and introducing published studies conducted in dyspasic patients with precise stimulation parameters, demographics and study design.

  23. 23.

    Wang Z, Song WQ, Wang L. Application of noninvasive brain stimulation for post-stroke dysphagia rehabilitation. Kaohsiung J Med Sci. 2017;33(2):55–61.

  24. 24.

    Vasant DH, Michou E, Mistry S, Rothwell JC, Hamdy S. High frequency focal repetitive cerebellar stimulation induces prolonged increases in human pharyngeal motor cortex excitability. J Physiol. 2015;593(22):4963–77.

  25. 25.

    Nitsche MA, Fricke K, Henschke U, Schlitterlau A, Liebetanz D, Lang N, et al. Pharmacological modulation of cortical excitability shifts induced by transcranial direct current stimulation in humans. J Physiol. 2003;553(Pt 1):293–301.

  26. 26.

    Nitsche MA, Paulus W. Excitability changes induced in the human motor cortex by weak transcranial direct current stimulation. J Physiol. 2000;527(Pt 3):633–9.

  27. 27.

    Nitsche MA, Seeber A, Frommann K, Klein CC, Rochford C, Nitsche MS, et al. Modulating parameters of excitability during and after transcranial direct current stimulation of the human motor cortex. J Physiol. 2005;568(Pt 1):291–303.

  28. 28.

    Suntrup S, Teismann I, Wollbrink A, Winkels M, Warnecke T, Flöel A, et al. Magnetoencephalographic evidence for the modulation of cortical swallowing processing by transcranial direct current stimulation. NeuroImage. 2013;83:346–54.

  29. 29.

    Vasant DH, Mistry S, Michou E, Jefferson S, Rothwell JC, Hamdy S. Transcranial direct current stimulation reverses neurophysiological and behavioural effects of focal inhibition of human pharyngeal motor cortex on swallowing. J Physiol. 2014;592(4):695–709.

  30. 30.

    Kumar S, Wagner CW, Frayne C, Zhu L, Selim M, Feng W, et al. Noninvasive brain stimulation may improve stroke-related dysphagia: a pilot study. Stroke. 2011;42(4):1035–40.

  31. 31.

    Yang EJ, Baek SR, Shin J, Lim JY, Jang HJ, Kim YK, et al. Effects of transcranial direct current stimulation (tDCS) on post-stroke dysphagia. Restor Neurol Neurosci. 2012;30(4):303–11.

  32. 32.

    Shigematsu T, Fujishima I, Ohno K. Transcranial direct current stimulation improves swallowing function in stroke patients. Neurorehabil Neural Repair. 2013;27:363–9.

  33. 33.

    Ahn YH, Sohn HJ, Park JS, Ahn TG, Shin YB, Park M, et al. Effect of bihemispheric anodal transcranial direct current stimulation for dysphagia in chronic stroke patients: a randomized clinical trial. J Rehabil Med. 2017;49(1):30–5.

  34. 34.

    Satoh Y, Tsuji K, Tsujimura T, Ishizuka K, Inoue M. Suppression of the swallowing reflex by stimulation of the red nucleus. Brain Res Bull. 2015;116:25–33.

  35. 35.

    Tsujimura T, Tsuji K, Magara J, Sakai S, Suzuki T, Nakamura Y, et al. Differential response properties of peripherally and cortically evoked swallows by electrical stimulation in anesthetized rats. Brain Res Bull. 2016;122:12–8.

  36. 36.

    Tsujimura T, Tsuji K, Ariyasinghe S, Fukuhara T, Yamada A, Hayashi H, et al. Differential involvement of two cortical masticatory areas in modulation of the swallowing reflex in rats. Neurosci Lett. 2012;528(2):159–64.

  37. 37.

    Sörös P, Al-Otaibi F, Wong SW, Shoemaker JK, Mirsattari SM, Hachinski V, et al. Stuttered swallowing: electric stimulation of the right insula interferes with water swallowing. A case report. BMC Neurol. 2011;11:20.

  38. 38.

    Yoshida Y, Tanaka Y, Hirano M, Nakashima T. Sensory innervation of the pharynx and larynx. Am J Med. 2000;108(Suppl 4a):51S–61S.

  39. 39.

    Steele CM, Miller AJ. Sensory input pathways and mechanisms in swallowing: a review. Dysphagia. 2010 Dec;25(4):323–33.

  40. 40.

    Hays SA, Rennaker RL, Kilgard MP. Targeting plasticity with vagus nerve stimulation to treat neurological disease. Prog Brain Res. 2013;207:275–99.

  41. 41.

    Martin RE. Neuroplasticity and swallowing. Dysphagia. 2009;24(2):218–29.

  42. 42.

    Hamdy S, Rothwell JC, Aziz Q, Singh KD, Thompson DG. Long-term reorganization of human motor cortex driven by short-term sensory stimulation. Nat Neurosci. 1998;1(1):64–8.

  43. 43.

    Fraser C, Power M, Hamdy S, Rothwell J, Hobday D, Hollander I, et al. Driving plasticity in human adult motor cortex is associated with improved motor function after brain injury. Neuron. 2002;34(5):831–40.

  44. 44.

    Jayasekeran V, Singh S, Tyrrell P, Michou E, Jefferson S, Mistry S, et al. Adjunctive functional pharyngeal electrical stimulation reverses swallowing disability after brain lesions. Gastroenterology. 2010;138(5):1737–46.

  45. 45.

    • Suntrup S, Teismann I, Wollbrink A, Winkels M, Warnecke T, Pantev C, et al. Pharyngeal electrical stimulation can modulate swallowing in cortical processing and behavior—magnetoencephalographic evidence. Neuroimage. 2015;104:117–24. This study found that pharyngeal electrical stimulation induces sustained alternation of swallowing-related cortical activity, accompanied with improvements in swallowing performance.

  46. 46.

    Takatsuji H, Zakir HM, Mostafeezur RM, Saito I, Yamada Y, Yamamura K, et al. Induction of the swallowing reflex by electrical stimulation of the posterior oropharyngeal region in awake humans. Dysphagia. 2012;27(4):473–80.

  47. 47.

    Tsukano H, Taniguchi H, Hori K, Tsujimura T, Nakamura Y, Inoue M. Individual-dependent effects of pharyngeal electrical stimulation on swallowing in healthy humans. Physiol Behav. 2012;106(2):218–23.

  48. 48.

    • Scutt P, Lee HS, Hamdy S, Bath PM. Pharyngeal electrical stimulation for treatment of poststroke dysphagia: individual patient data meta-analysis of randomised controlled trials. Stroke Res Treat. 2015;2015:429053. This review article showed that application of PES reduces radiological aspiration and clinical dysphagia in poststroke dysphagia patients using a meta-analysis of three randomized controlled clinical trials.

  49. 49.

    Restivo DA, Hamdy S. Pharyngeal electrical stimulation device for the treatment of neurogenic dysphagia: technology update. Med Devices (Auckl). 2018;11:21–6.

  50. 50.

    Low J, Reed A. Electrical stimulation of nerve and muscle. In low J, Reed A. Electrotherapy explained: principles and practice, ed 3. Oxford: Buttlerworth-Heinemann; 2000.

  51. 51.

    Miller S, Jungheim M, Kühn D, Ptok M. Electrical stimulation in treatment of pharyngolaryngeal dysfunctions. Folia Phoniatr Logop. 2013;65(3):154–68.

  52. 52.

    Chen YW, Chang KH, Chen HC, Liang WM, Wang YH, Lin YN. The effects of surface neuromuscular electrical stimulation on post-stroke dysphagia: a systemic review and meta-analysis. Clin Rehabil. 2016;30(1):24–35.

  53. 53.

    Gallas S, Marie JP, Leroi AM, Verin E. Sensory transcutaneous electrical stimulation improves post-stroke dysphagic patients. Dysphagia. 2010;25(4):291–7.

  54. 54.

    • Cugy E, Leroi AM, Kerouac-Laplante J, Dehail P, Joseph PA, Gerardin E, et al. Effect of submental sensitive transcutaneous electrical stimulation on virtual lesions of the oropharyngeal cortex. Ann Phys Rehabil Med. 2016;59(2):94–9. This study found that that submental sensitive transcutaneous electrical stimulation reversed the inhibitory effects on swallowing induced by virtual lesion, and suggested transcutaneous electrical stimulation can induce neuroplasticity.

  55. 55.

    Furuta T, Takemura M, Tsujita J, Oku Y. Interferential electric stimulation applied to the neck increases swallowing frequency. Dysphagia. 2012;27(1):94–100.

  56. 56.

    Nemec H. Interferential therapy: a new approach in physical medicine. Br J Physiother. 1959;12:9–12.

  57. 57.

    Theurer JA, Bihari F, Barr AM, Martin RE. Oropharyngeal stimulation with air-pulse trains increases swallowing frequency in healthy adults. Dysphagia. 2005;20(4):254–60.

  58. 58.

    Theurer JA, Czachorowski KA, Martin LP, Martin RE. Effects of oropharyngeal air-pulse stimulation on swallowing in healthy older adults. Dysphagia. 2009;24(3):302–13.

  59. 59.

    Theurer JA, Johnston JL, Fisher J, Darling S, Stevens RC, Taves D, et al. Proof-of-principle pilot study of oropharyngeal air-pulse application in individuals with dysphagia after hemispheric stroke. Arch Phys Med Rehabil. 2013;94(6):1088–94.

  60. 60.

    Turkington LG, Ward EC, Farrell AM. Carbonation as a sensory enhancement strategy: a narrative synthesis of existing evidence. Disabil Rehabil. 2017;39(19):1958–67.

  61. 61.

    Gatto AR, Cola PC, Silva RG, Spadotto AA, Ribeiro PW, Schelp AO, et al. Sour taste and cold temperature in the oral phase of swallowing in patients after stroke. Codas. 2013;25(2):164–8.

  62. 62.

    Pauloski BR, Logemann JA, Rademaker AW, Lundy D, Sullivan PA, Newman LA, et al. Effects of enhanced bolus flavors on oropharyngeal swallow in patients treated for head and neck cancer. Head Neck. 2013;35(8):1124–31.

  63. 63.

    Mulheren RW, Kamarunas E, Ludlow CL. Sour taste increases swallowing and prolongs hemodynamic responses in the cortical swallowing network. J Neurophysiol. 2016;116(5):2033–42.

  64. 64.

    • Elshukri O, Michou E, Mentz H, Hamdy S. Brain and behavioral effects of swallowing carbonated water on the human pharyngeal motor system. J Appl Physiol 2016;120(4):408–15. doi: This study found that sour taste bolus stimulation increased corticobulbar excitability up to 1 hour, and suggested sour taste stimulation can induce neuroplasticity.

  65. 65.

    Simons CT, Dessirier JM, Carstens MI, O’Mahony M, Carstens E. Neurobiological and psychophysical mechanisms underlying the oral sensation produced by carbonated water. J Neurosci. 1999;19(18):8134–44.

  66. 66.

    Arai T, Ohkuri T, Yasumatsu K, Kaga T, Ninomiya Y. The role of transient receptor potential vanilloid-1 on neural responses to acids by the chorda tympani, glossopharyngeal and superior laryngeal nerves in mice. Neuroscience. 2010;165(4):1476–89.

  67. 67.

    Yamamura K, Kurose M, Okamoto K. Chemical sensing regulates mastication/swallowing. Curr Pharm Des. 2016;22(15):2279–84.

  68. 68.

    Kitagawa J, Shingai T, Takahashi Y, Yamada Y. Pharyngeal branch of the glossopharyngeal nerve plays a major role in reflex swallowing from the pharynx. Am J Physiol Regul Integr Comp Physiol. 2002;282(5):R1342–7.

  69. 69.

    Magara J, Michou E, Raginis-Zborowska A, Inoue M, Hamdy S. Exploring the effects of synchronous pharyngeal electrical stimulation with swallowing carbonated water on cortical excitability in the human pharyngeal motor system. Neurogastroenterol Motil. 2016;28(9):1391–400.

Download references

Author information

Correspondence to Kensuke Yamamura.

Ethics declarations

Conflict of Interest

Kensuke Yamamura holds a patent (#6049010) with the Japan Patent Office.

Masayuki Kurose and Keiichiro Okamoto declare that they have no competing interests.

Human and Animal Rights and Informed Consent

This article does not contain any studies with human or animal subjects performed by any of the authors.

Additional information

This article is part of the Topical Collection on Swallowing Disorders

Rights and permissions

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Yamamura, K., Kurose, M. & Okamoto, K. Guide to Enhancing Swallowing Initiation: Insights from Findings in Healthy Subjects and Dysphagic Patients. Curr Phys Med Rehabil Rep 6, 178–185 (2018).

Download citation


  • Swallowing
  • Swallowing initiation
  • Stimulation
  • Plasticity
  • Dysphagia
  • Review