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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
TRIPLE
Enrollment
90
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.
The Hong Kong Polytechnic University
Hung Hom, Kowloon, Hong Kong
RECRUITINGAverage 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.
Time frame: 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 - 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: First day of intervention, 1 day and 2 months after the last day of intervention (3 time points, up to 2 months)
This platform is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional.