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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Date data sharing statement initially provided
Date results information initially provided
Type of registration
Retrospectively registered

Titles & IDs
Public title
The impact of brain stimulation on planning abilities in healthy adults
Scientific title
The impact of anodal and cathodal transcranial direct current stimulation on executive functioning in healthy adults
Secondary ID [1] 282109 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Executive decline in older people (planning abilities) 288604 0
Condition category
Condition code
Neurological 288936 288936 0 0
Studies of the normal brain and nervous system
Mental Health 289157 289157 0 0
Studies of normal psychology, cognitive function and behaviour

Study type
Description of intervention(s) / exposure
transcranial direct current stimulation (tDCS) will be used in the current study. tDCS is safe, non-invasive form of brain-modulation. Using a common 9 volt battery, tDCS sends a weak DC current through two sponge electrodes placed upon the scalp and held in place using an elastic strap.

tDCS modifies spontaneous neuronal excitability via a tonic hypo- or hyperpolarization of neuronal resting membrane potential. Depending upon the polarity of the current flow, regional excitability can either be increased (anodal tDCS) or decreased (cathodal tDCS).

The tDCS device itself is rather simple. A single 9 volt battery powers a constant current generator that delivers current between two electrodes: a cathode (negative charge) and an anode (positive charge). When delivering tDCS, these electrodes (which can vary in size, shape, and basic material) are placed directly on the scalp. The constant current generated by the tDCS device flows from the cathode (-) to the anode (+) thereby creating a circuit directly through the brain.

Several parameters determine the effects and efficacy of tDCS. The first, and perhaps most important, of these parameters is electrode position. As the neural effect of each electrode differs, it is essential the target being stimulated and the polarity of stimulation be determined and understood prior to application. Typically, the desired electrode is placed directly over the intended target whilst the second electrode is placed in either a neutral (vertex, orbital bone, &c.) or related (contralateral neural region) reference location. The next parameter is electrode size. As can be assumed, electrodes come in many sizes (typically from 1 cm2 to 35 cm2). Although larger electrodes affect a larger area of underlying cortex, an increase in the electrode surface area necessarily decreases the amount of current generated at each point. Accordingly, proper electrode size is essential to elicit desired effects. Another parameter is current density. Determined by dividing the current strength (typically between 0.01 and 2.0 mA) by the electrode size, the current density determines the induced field strength in the brain and, accordingly, tDCS effects. It has been shown in humans that larger current densities generate stronger and longer lasting effects. The final parameter essential to tDCS is stimulation duration. The duration of stimulation typically determines the duration of tDCS after-effects.

For this study, 60 healthy participants will undergo one session of tDCS. During this session, 2 mA of tDCS will be applied for 20 minutes over the dorsal lateral prefrontal cortex (DLPFC). Each sponge electrode will be 9 cm2. As tDCS creates a small electric current between two poles, there are two unique electrodes : a positive anode and a negative cathode. Typically, the neural region under the positive anode becomes hypo-polarized thereby making the underlying neurons more likely to fire. Conversely, the neural region under the negative cathode becomes hyperpolarized thereby making the underlying neurons less likely to fire. Due to these dual electrode effects, it is important to have two stimulatory conditions: each condition will have the electrodes placed in the same areas, however the anode and cathode will be switched. The position of the electrodes will be defined as:

Primary Electrode: We will place the primary electrode over the right DLPFC in accord with the standard 10/20 system. Tweny the participants will have the positive anode placed in this location, twenty will have the negative cathode placed here, and twenty participants will receive no stimulation (control group). Participants who receive no stimulation will still have a primary electrode applied to the scalp, however, in this condition polarity will not matter as stimulation will only last for 30-seconds: just long enough to generate a slight tingle and blind the subject to his/her condition but not long enough to generate any effect.

Secondary Electrode: We will place the secondary electrode over the left dorsal lateral prefrontal cortex in accord with the standard 10/20 system.1 The secondary electrode will be the opposite polarity of the primary electrode: accordingly, those with a positive anode as the primary electrode will have the negative cathode as the secondary, and vice versa.

The tDCS device to be used in the current study is the Iontophoresis Device (trade name Chattanooga Ionto)
Intervention code [1] 286815 0
Treatment: Devices
Comparator / control treatment
The same tDCS device will be used in the control group. The control group will receive sham stimulation - whereby the tDCS machine is turned on for 30 seconds and then ramped down to no stimulation.
Control group

Primary outcome [1] 289180 0
The Stockings of Cambridge (SOC) task will provide the primary measure of executive function. This will be done on the CANTAB, a touch-screen computer.This task assesses a person's planning ability by measuring how well they are able to mentally manipulate the positions of coloured balls and plan the moves that are required to replicate a pre-determined configuration. During the test, participants will be presented with two displays on the computer screen, top display and bottom display. Each of the displays contains three coloured balls held in a stocking suspended from a beam. Participants are required to move the balls in the bottom display, one at a time so that they match the configuration of the top display. Participants will complete 2, 3, 4 and 5 move problems. Performance will be measured by calculating mean number of moves a participant makes for each of the problems such that a lower mean is indicative of better performance.
Timepoint [1] 289180 0
This will be measured immediately pre-tDCS and immediately post-tDCS
Primary outcome [2] 289181 0
A Spatial Working Memory (SWM) task will be used as a second measure of executive function. This will be done on the CANTAB, a touch-screen computer. This task assesses a person’s spatial working memory by measuring their ability to systematically search for hidden tokens behind boxes without returning to the boxes where tokens have appeared before. During the task, participants will be presented with a number of boxes on the screen. They will be required to touch each of the boxes to reveal a hidden token which they will have to subsequently drag and drop into a empty column located on the right hand side of the screen. At any one time, there will only be a single token on the screen and tokens will not appear in the same box twice. Performance on this task is based on the number of search errors made such that the less errors a participant makes, the better their performance.
Timepoint [2] 289181 0
This will be measured immediately pre-tDCS and immediately post-tDCS
Primary outcome [3] 289182 0
A computerised Stroop task will be used as a measure of executive function. This task assesses the ability to direct attention and inhibit irrelevant material. If a word is displayed in a color different from the color it actually names (for example, the word green written in red ink), participants take longer to name the word than if the word is displayed in a colour the same as the word (for example, green written in green ink) . Participants will see a number of word colours displayed in either the same colour ink (congruent trial) or a different colour (incongruent trials) and will be asked to identify the word presented by pressing the left or right mouse key. Participants will complete 120 trials in total.
Timepoint [3] 289182 0
This will be measured immediately pre-tDCS and immediately post-tDCS
Secondary outcome [1] 301970 0
The Intra/Extra Dimensional Set (IED) task will assess attention. This will be done using the CANTAB. This task assesses a person’s ability to acquire rules and reverse them. This test involves visual discrimination, attention set formation and also the maintenance, shifting and flexibility of attention. During the test, four boxes appear on the computer screen. Two of these boxes will contain stimuli. Participants are required to select the correct stimuli by touching it. This correct stimuli is identified based or trial and error. Feedback will be provided via the computer screen to indicate if a selection is right or wrong. Depending on the feedback, participants will develop an underlying rule or mental set for the correct stimuli. Two dimensions of stimuli are used, colour filled shapes and white lines. During 9 blocks of this test, participants are required to alternately maintain attention to different examples within a reinforced mental set (i.e., intradimensional shift) and then shift attention to a previously irrelevant stimulus dimension (i.e., extradimensional shift). The stimuli can either be simple or compound. Simple stimuli comprises of one of the mentioned dimensions while compound stimuli comprises of both. Once a criterion of 6 consecutive correct answers is reached, the next block commences. Performance is measured by the measuring the total number of errors made, such that the less errors a participant makes, the better their performance.
Timepoint [1] 301970 0
This will be measured immediately pre-tDCS and immediately post-tDCS

Key inclusion criteria
The participants must be aged between 18 and 80 years old.
Minimum age
18 Years
Maximum age
80 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Individuals cannot participate in this research project if they have had any of the following procedures or if any of the following conditions apply to them:

Any neurological disorder or brain surgery

Any history of epilepsy

Currently taking psychoactive medication

Any active skin disease (such as eczema) on the scalp

Any unstable medical condition (for example, un-controlled diabetes)

Any history of migraine

Any history of episodes of faintness (one isolated incident is not an episode)

Any history of asthma

Any metal implants or devices in your body (e.g. surgical clip, coronary stent)
Note: metal dental fillings or metal dental braces will not exclude you from participating.

Currently using a hearing aid

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
A participant (once deemed suitable) will be informed that they will be allocated to one of three intervention conditions but will not be informed of the condition until their completion of the study. Using central randomisation by a computer, the participant will be assigned a number which corresponds with a condition (1 = control, 2= anode right, cathoe left, 3 = cathode right, anode left).
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Random number generation in Excel, where numbers 1, 2 & 3 will be sorted randomly and assigned to a participant number within Excel.
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s

Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis
Analysis of variance (ANOVA) will be used, with tDCS condition (control, anode, cathode) as the between-groups factor and time (pre, post) as the within groups factor. This will be done for each measure separately, with follow-up adjusted pairwise comparisons to explore any interactions.
. Power calculations using g-Power reveal this to be the appropriate number of participants for this study. I anticipate moderate effect sizes (p=.05, power .60); therefore following recommendations from the statistical literature, a minimum of 20 participants per group are required to perform an analysis of variance (ANOVA) with three independent groups. The sample size oparticipants in previous studies involving tDCS have ranged from 8 to 25 per group and for previous studies involving a wider variety of tDCS stimulation sites, the total sample size has ranged from 16 to 85 participants. A minimum sample of 60 participants should therefore ensure that analyses are sufficiently powered.

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)

Funding & Sponsors
Funding source category [1] 286963 0
Name [1] 286963 0
Curtin University
Address [1] 286963 0
GPO Box U1987
Country [1] 286963 0
Primary sponsor type
Curtin University
GPO Box U1987
Secondary sponsor category [1] 285753 0
Name [1] 285753 0
Address [1] 285753 0
Country [1] 285753 0

Ethics approval
Ethics application status
Ethics committee name [1] 289012 0
Curtin University Human Research Ethics Committee
Ethics committee address [1] 289012 0
Office of Research and Development
Curtin University
GPO Box U1987
Perth, WA
Ethics committee country [1] 289012 0
Date submitted for ethics approval [1] 289012 0
Approval date [1] 289012 0
Ethics approval number [1] 289012 0
HR 32/2013

Brief summary
The present study examines whether transcranial direct current stimulation (tDCS) over the left dorsal lateral prefrontal cortex (DLPFC) impacts upon executive functioning in healthy older adults. Based on previous research, the following particular hypotheses may be proposed:

(i) older adults will perform poorly on tests of executive function compared to younger adults

(ii) anodal (excitatory) tDCS of left DLPFC will enhance performance on measures of executive functioning in older adults

(iii) cathodal (inhibitory) tDCS of left DLPFC will lead to decreased performance on measures of executive functioning in older adults

(iv) sham tDCS of left DLPFC will not impact upon performance on measures of executive function
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 38422 0
Dr Andrea Loftus
Address 38422 0
School of Psychology and Speech Pathology
Curtin University
GPO Box U9187
Country 38422 0
Phone 38422 0
+61 8 9226 2308
Fax 38422 0
Email 38422 0
Contact person for public queries
Name 38423 0
Dr Andrea Loftus
Address 38423 0
School of Psychology and Speech Pathology
Curtin University
GPO Box U9187
Country 38423 0
Phone 38423 0
+61 8 9226 2308
Fax 38423 0
Email 38423 0
Contact person for scientific queries
Name 38424 0
Dr Andrea Loftus
Address 38424 0
School of Psychology and Speech Pathology
Curtin University
GPO Box U9187
Country 38424 0
Phone 38424 0
+61 8 9226 2308
Fax 38424 0
Email 38424 0

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
No/undecided IPD sharing reason/comment
What supporting documents are/will be available?
No other documents available
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary
The findings indicated that brain stimulation did not impact upon executive function in odler adults. Further research is required.