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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Prospectively registered

Titles & IDs
Public title
The influence of cerebellar transcranial direct current stimulation (tDCS) on motor learning in swallowing
Scientific title
The effect of cerebellar transcranial direct current stimulation (tDCS) while performing a swallowing skill task on motor skill-learning in healthy individuals compared to sham treatment.
Secondary ID [1] 286298 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Dysphagia 294383 0
Condition category
Condition code
Physical Medicine / Rehabilitation 294693 294693 0 0
Speech therapy
Oral and Gastrointestinal 295225 295225 0 0
Other diseases of the mouth, teeth, oesophagus, digestive system including liver and colon

Study type
Description of intervention(s) / exposure
The study has three arms
Arm 1: anodal tDCS
Arm 2: cathodal tDCS
Arm 3: sham.

The cerebellar tDCS set up will be made for each participant in the three groups. This involves the attachment of three rectangular saline-soaked sponge electrodes (5×5 cm, surface area 25 cm^2) to the participants head. One will be placed on each cheek and the third one will be placed over the cerebellum (back of the head). The sponge electrodes will be connected to an electrically tested, registered stimulation device, tDCS Transcranial Stimulation Kit (TCT Research Limited), that applies a standard level of current (2mA) for 20 min while participants perform the swallowing tasks. Stimulation via these parameters induces a current at a density of 0.08 mA/cm^2. Using this set up the participant will be asked to perform two training sessions on consecutive days.
During the training, muscle activity during swallowing will be measured via sEMG electrodes placed under the chin (submental muscles). The measured activity will be displayed on a computer screen, thereby providing feedback to the participant about the accuracy of their swallowing movements in real time. Participants will be asked to swallow every 30 seconds and manipulate their muscle activity so that the waveform on the screen touches a target box displayed on the same screen. The accuracy of each swallow will be displayed to the participants immediately on completion of that swallow.

All participants will be asked to perform this swallowing task (the same for each participant) and will receive one of three types of tDCS (anodal, cathodal or sham). A certified clinician (speech and language therapist and PhD student) closely supervised by a research team that has a history in evaluating neurorehabilitation techniques and the use of non-invasive brain stimulation techniques, will administer the intervention.
Intervention code [1] 291327 0
Intervention code [2] 291328 0
Treatment: Devices
Comparator / control treatment
Sham control group.
Participants in this group will undergo the same procedure and obtain the same setup as the other two groups (anodal and cathodal stimulation). However, this group will not receive any direct current stimulation during the swallowing skill training task.
Control group

Primary outcome [1] 294452 0
Swallowing accuracy will be assessed by the peak-target error.
Each swallow of the participants will be displayed as a waveform on the computer screen by measuring muscle activity via surface electromyography. The participants will be asked to swallow such that the peak of the waveform hits a small target on the screen.
The peak-target error will be generated out of the two distances (along the X- and Y-Axis) between the target and the actual swallowing performance (peak of the displayed sEMG data taken from muscles involved in swallowing) of the participant in each trial. The error will be calculated as: z= [(Ax/trial length)^2+ (Ay/calibration value)^2]^(1/2)
Timepoint [1] 294452 0
Baseline measurements and assessment swallows over four sessions (2 consecutive days, follow-up on day one and day seven after the training).
Secondary outcome [1] 313352 0
Timepoint [1] 313352 0

Key inclusion criteria
Healthy individuals aged between 50 – 80 years of age with no history of neurological impairment, current symptoms of dysphagia, drug use that would affect neural or swallowing function or vision.
Minimum age
50 Years
Maximum age
No limit
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Individuals who have metallic implants in their brain, had undergone recent brain neurosurgery, or anatomical changes that may modify current flow will be excluded.

Study design
Purpose of the study
Allocation to intervention
Non-randomised trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Participants will be recruited through advertising flyers in public and private institutions (with permission) around Christchurch, such as shopping malls (e.g. The Palms, Northlands Mall), theatres (e.g. Isaac Royal Theatre, The Court Theatre), and community organisations (e.g. Senior Citizen Clubs, Choirs). Furthermore, talks will be given by the lead investigator informing potential participants about this study in different community organizations. After these presentations the advertising flyers will be posted on easily accessible social boards for the audience. Anyone interested can contact the lead investigator directly through the information on the flyer.

The participant will then be allocated to one of the three experimental groups (anodal, cathodal, or sham).
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Gender and age will be used to counterbalance the participants into three groups (anodal, cathodal, and sham tDCS) of 12 participants each. A research assistant will assign the participant into one group, matching by gender and age, by writing the participant number into an appropriate cell on an allocation spreadsheet. The same research assistant will attach the sponge electrodes to the participants head. For the sham condition, the research assistant can randomly choose between the anodal or cathodal set up as no stimulation is provided through the electrodes. For blinding purposes, an opaque surgical cap will cover the electrodes. The research assistant will also be in charge of programming the tDCS device into the appropriate setting and starting the stimulation during the training. Research students working in the swallowing lab will function as research assistants in this study. They will all be well educated in how to assign participants into the different groups, setting the participant up for tDCS, and operating the tDCS device. The research assistants will treat all participant information confidentially and are not allowed to let the participant know which type of stimulation they will receive. The allocation spreadsheet will not be accessible to the lead investigator and will be stored in a locked cabinet when not in use.
The lead investigator will leave the room while the participant is prepared for the session. Once the setup is finished, the lead investigator is allowed to enter the room again and will start the training session. This procedure will allow the lead investigator and participant to remain blinded to the allocated group and balance the assignment for age and gender.
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s
The people administering the treatment/s

Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis
To analyse the difference between the three groups a one-way ANOVA followed by post hoc comparison tests will be performed. Furthermore, paired t-tests will be performed to determine to learning effects within each group and between sessions.

In the absence of pre-existing data for the proposed pilot study a calculation of sample size is not possible. The sample size is aligned to comparable studies conducted in limb function studies and cortical tDCS studies of swallowing.

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment outside Australia
Country [1] 6712 0
New Zealand
State/province [1] 6712 0

Funding & Sponsors
Funding source category [1] 290856 0
Name [1] 290856 0
The University of Canterbury Rose Centre for Stroke Recovery and Research
Address [1] 290856 0
St George’s Medical Centre
Leinster Chambers, Level One
Private Bag 4737
249 Papanui Road
Christchurch 8014
Country [1] 290856 0
New Zealand
Funding source category [2] 291172 0
Name [2] 291172 0
The University of Canterbury New Zealand Brain Research Doctoral Scholarship
Address [2] 291172 0
Scholarships Office
University of Canterbury
Student Service Centre
Level 1, Matariki
Private Bag 4800
Christchurch 8140
Country [2] 291172 0
New Zealand
Primary sponsor type
The University of Canterbury Rose Centre for Stroke Recovery and Research
St George’s Medical Centre
Leinster Chambers, Level One
Private Bag 4737
249 Papanui Road
Christchurch 8014
New Zealand
Secondary sponsor category [1] 289851 0
Name [1] 289851 0
Address [1] 289851 0
Country [1] 289851 0

Ethics approval
Ethics application status
Ethics committee name [1] 292472 0
Health and Disability Committees
Ethics committee address [1] 292472 0
Ministry of Health
Ethics Department
Reception - Ground Floor
20 Aitken Street
Wellington 6144
Ethics committee country [1] 292472 0
New Zealand
Date submitted for ethics approval [1] 292472 0
Approval date [1] 292472 0
Ethics approval number [1] 292472 0
Ethics committee name [2] 292713 0
University of Canterbury Maori Consultation
Ethics committee address [2] 292713 0
Dr. Tracy Rohan
Research & Innovation
University of Canterbury
Private Bag 4800
Christchurch 8140
Ethics committee country [2] 292713 0
New Zealand
Date submitted for ethics approval [2] 292713 0
Approval date [2] 292713 0
Ethics approval number [2] 292713 0

Brief summary
The use of non-invasive brain stimulation offers promising opportunities to enhance motor function and motor learning in numerous rehabilitation areas. Transcranial direct current stimulation (tDCS) is a form of non-invasive brain stimulation. This technique uses a low direct current to evoke changes in brain excitability. Brain function can either be enhanced with anodal stimulation (positive polarity) or inhibited with cathodal stimulation (negative polarity) with current delivered through sponge electrodes on the person’s head over the targeted brain region. One possible placement for stimulation is the cerebellum which has a primary role in the coordination of movements and error correction. Applying tDCS over the cerebellum has been shown to enhance motor skill-learning in limb rehabilitation. However it is not known whether these effects also occur for corticobulbar-related motor functions, such as swallowing.

The proposed research will investigate the effects of cerebellar tDCS on motor learning in swallowing in 36 healthy individuals. Each participant will be asked to complete two sessions of swallowing skill-training on two consecutive days. There will be one follow-up on day three and a second follow-up after one week. A behavioural training protocol, Biofeedback in Strength and Skill Training (BiSSkiT), will be used to increase precision and timing of swallowing as indicated by floor-of-mouth muscle contraction during swallowing using surface electromyography (sEMG) biofeedback. The feedback for the participant will be displayed as a real time waveform on a computer screen. The amplitude of the waveform will alter depending on the strength of floor-of-mouth muscle contraction during swallowing. For the swallowing training, the participant will be asked to hit a small target on the screen with the peak of the waveform. The target will move in position on each screen (every 30 seconds) to increase volitional control of swallowing by changing timing and amplitude of swallowing in each trial. Swallowing performance will be measured by calculating the peak-target error out of the distances between the highest peak of the waveform and the centre of the target. This measure will also be the baseline measure before and assessment swallows after the training and for the follow-ups. However, to assess learning, for the assessment swallows no feedback in form of a waveform will be provided.

The swallowing task will be performed with and without cerebellar tDCS. Comparison between tasks will provide information about stimulation effects on motor learning. These findings will then be used to investigate parameters of cerebellar stimulation, such as dose, retention of skill, and electrode placement. This information may be used to determine the benefits of cerebellar tDCS on patients with swallowing disorders (dysphagia) to guide the development of effective dysphagia rehabilitation protocols.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 55478 0
Miss Kerstin Erfmann
Address 55478 0
The University of Canterbury Rose Centre for Stroke Recovery and Research at St George’s Medical Centre
Leinster Chambers, Level One
Private Bag 4737
249 Papanui Road
Christchurch 8014
Country 55478 0
New Zealand
Phone 55478 0
+64 3 364 2307
Fax 55478 0
+64 3 375 6267
Email 55478 0
Contact person for public queries
Name 55479 0
Miss Kerstin Erfmann
Address 55479 0
The University of Canterbury Rose Centre for Stroke Recovery and Research at St George’s Medical Centre
Leinster Chambers, Level One
Private Bag 4737
249 Papanui Road
Christchurch 8014
Country 55479 0
New Zealand
Phone 55479 0
+64 3 364 2307
Fax 55479 0
Email 55479 0
Contact person for scientific queries
Name 55480 0
Miss Kerstin Erfmann
Address 55480 0
The University of Canterbury Rose Centre for Stroke Recovery and Research at St George’s Medical Centre
Leinster Chambers, Level One
Private Bag 4737
249 Papanui Road
Christchurch 8014
Country 55480 0
New Zealand
Phone 55480 0
+64 3 364 2307
Fax 55480 0
Email 55480 0

No information has been provided regarding IPD availability
Summary results
No Results