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Background: Transcranial Direct Current Stimulation (tDCS) is a form of non-invasive brain stimulation that has aroused increased interests in the past decade. Not only that it is transient with little side-effects, and can be well-tolerated by children, it is also affordable and readily accessible, making it an appealing treatment option for autism spectrum disorder (ASD).
Objective: (1) To assess the therapeutic effects of tDCS when combined with cognitive training for 10 consecutive weekdays on improving cognitive processing in children with ASD, relative to control group receiving sham-stimulation, and (2) to evaluate the associated neural mechanisms underlying the treatment effect of tDCS on children with ASD.
Methods: To assess the therapeutic effects of tDCS, 90 adolescents with ASD (age 6-12 years) will be randomly assigned to active- (n=45), or sham- (n=45) tDCS groups. Twenty-minute sessions of tDCS stimulation to the left dorsolateral prefrontal cortex (DLPRC) will be provided on 10 consecutive weekdays, in conjunction with cognitive training exercises. Participants with a head circumference of less than 53 cm will receive 1.0 mA of stimulation, while those with a circumference of 53 cm or greater will receive 1.5 mA. EEG, fNIRS and neuropsychological tests will be administered before, immediately after, and 2 months after the series of tDCS sessions.
Hypothesis: The investigators hypothesize that children with ASD who are randomly assigned to receive a montage of prefrontal tDCS, with cathode (inhibitory) placed over left DLPFC and anode (excitatory) over right supraorbital region) will evidence greater improvement in executive function (primary outcome) than children with ASD who are randomly assigned to receive sham-tDCS.
In addition to testing the primary clinical outcome, stated above, in planned exploratory analyses, the investigators will also examine the effects of tDCS on secondary outcome measures of cognitive function, including information processing speed, working memory, inhibitory control, and cognitive flexibility; and conduct exploratory mediation analyses to better understand the potential neurophysiological factors underlying the therapeutic effects of tDCS. This will include E/I ratio as exploratory mediator variables. As these secondary analyses are exploratory, the investigators will report them as such in presentations and published papers, and the investigators will not draw definitive conclusions from them. Rather, they will be used to better understand the potential impact of tDCS and the mechanisms underlying impact, and to inform future research.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Active-tDCS | Experimental | For active-tDCS condition, participants will receive stimulation on the dorsolateral prefrontal cortex with ramp up and ramp down mode for 10 seconds, eliciting a tingling sensation on the scalp that fades over seconds. |
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| Sham-tDCS | Sham Comparator | For sham-tDCS condition, participants will receive initial stimulation with ramp up and ramp down mode for 30 seconds, eliciting a tingling sensation on the scalp then it will be discontinued. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| tDCS with computerized cognitive training | Device | Participants will complete tDCS over 10 sessions in 2 weeks (once per day, for 10 consecutive working days), while performing the executive function training tasks. The training session will last for 20 minutes. |
| Measure | Description | Time Frame |
|---|---|---|
| Average standardised score of executive function tests | The executive function of the children with ASD will be assessed using the Executive Composite score, which will be derived by summing the scores from the test battery of executive functions. Simple-task processing speed will be evaluated using the CANTAB® 5-choice Reaction Time (RTI) task. Complex-task processing speed will be assessed using the computerized version of the Wisconsin Card Sorting Test (WCST). The mean reaction time is calculated for the trials giving a correct answer during WCST. The reaction time measured from both tasks will be converted to standard scores and averaged to yield an executive composite score. Lower scores indicate poorer executive functioning. | First day of intervention, 1 day and 2 months after the last day of intervention (3 time points, up to 2 months) |
| Measure | Description | Time Frame |
|---|---|---|
| Change in CANTAB® cognitive test - Reaction Time (RTI) | RTI assesses motor and mental response speeds, reaction time, response accuracy and impulsivity. It consists of 30 trials with five potential targets and requires participants to make flexible responses as fast as possible to the target stimulus (shown in yellow). Specifically, movement and reaction time will be measured, where shorter duration reflects faster processing speed. |
| Measure | Description | Time Frame |
|---|---|---|
| Exploratory mediator - excitability-inhibitory (E/I) ratio (indexed by EEG measures) | EEG resting-state theta coherence (4-7.5 Hz) will be computed from EEG signals collected from the 19 electrode positions collected from 5-min eye opened resting. Raw data will be processed with the EEGLAB Toolbox using MATLAB® R2019a. Automatic channel rejection, re-referencing, finite impulse response filtering will be performed. To filter artifacts, visual inspection of the EEG data will also be performed. Independent component analysis (ICA) will be used to further remove muscle and eyeblink artifacts. The E/I ratio will be calculated using the method described by Bruining et al (2020). the correlation between amplitude and fluctuation will be calculated for each EEG channel to yield the E/I ratio. |
Inclusion Criteria:
Exclusion Criteria:
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| Name | Role | Phone | Extension | |
|---|---|---|---|---|
| Yvonne Han, PhD | Contact | +852 2766 7578 | yvonne.han@polyu.edu.hk |
| Name | Affiliation | Role |
|---|---|---|
| Yvonne Han, PhD | The Hong Kong Polytechnic University | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| The Hong Kong Polytechnic University | Recruiting | Hung Hom | Kowloon | Hong Kong |
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| ID | Term |
|---|---|
| D000067877 | Autism Spectrum Disorder |
| ID | Term |
|---|---|
| D002659 | Child Development Disorders, Pervasive |
| D065886 | Neurodevelopmental Disorders |
| D001523 | Mental Disorders |
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| ID | Term |
|---|---|
| D065908 | Transcranial Direct Current Stimulation |
| ID | Term |
|---|---|
| D004599 | Electric Stimulation Therapy |
| D013812 | Therapeutics |
| D003295 | Convulsive Therapy |
| D013000 | Psychiatric Somatic Therapies |
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| First day of intervention, 1 day and 2 months after the last day of intervention (3 time points, up to 2 months) |
| Change in CANTAB® cognitive test - Stop Signal Task (SST) | SST assesses the ability of inhibition control. The participant must respond to an arrow stimulus, by selecting one of two options, depending on the direction in which the arrow points. If an audio tone is present, the subject must withhold making that response (inhibition). Accuracy will be measured, where higher accuracy indicates better inhibition control. | First day of intervention, 1 day and 2 months after the last day of intervention (3 time points, up to 2 months) |
| Change in CANTAB® cognitive test - Multitasking Test (MTT): Response Latencies | MTT assesses the ability to resolve the interference of task-irrelevant information (stroop-like effect). The test displays an arrow which can appear on either the left or right side of the screen and can point to either the left or right side. In each trial, participants are presented with a cue that indicates which button to press according to two different rules. And the rules that participants have to follow may change from trial to trial in a randomized order. Participant's response latencies will be measured. | First day of intervention, 1 day and 2 months after the last day of intervention (3 time points, up to 2 months) |
| Change in CANTAB® cognitive test - Multitasking Test (MTT): Error Scores | MTT assesses the ability to resolve the interference of task-irrelevant information (stroop-like effect). The test displays an arrow which can appear on either the left or right side of the screen and can point to either the left or right side. In each trial, participants are presented with a cue that indicates which button to press according to two different rules. And the rules that participants have to follow may change from trial to trial in a randomized order. Participant's error scores will be measured. | First day of intervention, 1 day and 2 months after the last day of intervention (3 time points, up to 2 months) |
| Change in CANTAB® cognitive test - Emotion Recognition Task (ERT) | ERT assesses ability to identify six basic emotions in facial expressions along a continuum of expression magnitude. The participants must select which emotion the facial image displayed 0.2s ago. Accuracy and its percentage, as well as response latencies will be measured. | First day of intervention, 1 day and 2 months after the last day of intervention (3 time points, up to 2 months) |
| Change in Verbal Fluency Test (VFT) | The VFT assesses an individual's ability of working memory retrieval and executive control by instructing the individual to generate words for given semantic categories within a limited time. The VFT experimental paradigm is designed and presented with E-prime 3 (Psychology Software Tools Inc., Sharpsburg, PA, USA). During the experimental blocks, which will be counterbalanced across individuals to avoid order effects, a category word (i.e. 'transportation' or 'country') will be shown on the screen. Participants will be asked to focus their eye gaze on the center of the screen and continuously repeat '1, 2, 3, 4' slowly during the given period of time. Their responses will be recorded by an audio recorder and then transferred into written form on an Excel spreadsheet. The number of unique and correct words generated will be counted for each of the participants. This test will be paired with fNIRS recording. | First day of intervention, 1 day and 2 months after the last day of intervention (3 time points, up to 2 months) |
| First day of intervention, 1 day and 2 months after the last day of intervention (3 time points, up to 2 months) |
| Oxyhemoglobin Concentration (measured by fNIRS) | fNIRS data will be collected from 15 channel positions and processed using the NIRSIT Lite Analysis Tool version 3.1.0 (OBELAB Inc., Seoul, Korea), which is a MATLAB® R2019a compatible graphical user interface. The raw light intensity data for resting-state and task-based recordings (i.e. VFT) will be converted into changes in oxyhemoglobin (oxy-Hb) concentration according to the modified Beer-Lambert Law. To remove the physiological noise and movement artifacts, a 0.005-0.05 Hz bandpass filter will be used. To avoid the contamination of data caused by head movements, which are observed as spikes or significant shifts from baseline values, two additional channel rejection measures will be taken. Baseline corrections will be performed for task-based recordings based on the mean pretask baseline values defined by 5s prior to the task blocks to control for task-irrelevant [oxy-Hb] changes. The block average fNIRS data will be used for subsequent statistical analyses. | First day of intervention, 1 day and 2 months after the last day of intervention (3 time points, up to 2 months) |
| D004191 | Behavioral Disciplines and Activities |
| D004597 | Electroshock |
| D011580 | Psychological Techniques |