tDCS and Motor Learning in Children With DCD

Transcranial direct-current stimulation (tDCS) is one of the most common non-invasive brain stimulation techniques but applications in pediatric populations are relatively unexplored. tDCS applies a weak electric current over the scalp to modulate cortical excitability. Anodal stimulation excites the stimulated brain region. Anodal tDCS applied to the motor cortex contralateral to the trained hand enhances motor learning across single or multiple day training sessions (Reis 2009). tDCS has shown promising effects in the developing brain including the potential to enhance motor skills that may then be transferred to other untrained skills in typically developing children (Ciechanski 2017). tDCS is safe and tolerable and a feasible technique with only mild short-term adverse effects (e.g., redness, tingling, itching, and burning sensation) in children. The adverse effects usually occur at electrode sites and disappear within a few minutes after stimulation starts (Krishnan 2015).

Combined with motor-based interventions, tDCS can enhance motor performance in adults (Reis 2009, 2011) and children (Gillick 2014; Grecco 2017; Kirton 2017; Moura 2016). It is currently being used in combination with other treatments (e.g., behavioural therapy and neurorehabilitation) in children and adolescents with neurodevelopmental disorders (Muszkat 2016), including Autism Spectrum Disorder (Amatachaya 2014) and Attention-Deficit/Hyperactivity Disorder (ADHD) (Bandeira 2016), as well as motor disorders such as Cerebral Palsy (Gillick 2014; Grecco 2017; Kirton 2017; Moura 2016). However, the effect of tDCS on skill motor learning in children with Developmental Coordination Disorder (DCD) is largely unexplored.

DCD is a chronic motor disorder of unknown etiology that affects 5-6% of school-aged children in Canada (APA, 2013). DCD interferes with children's academic achievement and limits their ability to participate in daily activities (e.g., printing, getting dressed, tying their shoes, riding a bike, using cutlery), as well as vocational activities, leisure, and play (APA, 2013).15 Subsequently, children may develop psychosocial difficulties, including low self-esteem, depression, anxiety, loneliness, problems with peers, and poor participation in physical and social activities (Zwicker 2013). DCD is a lifelong condition, and 75% of children with DCD will continue to experience motor difficulties as adults if they don't receive proper treatment (Kirby 2014). Up to half of children with DCD also have co-occurring ADHD (Piek 1999).

Several brain regions have been implicated in DCD, including the cerebellum, basal ganglia, parietal lobe, and parts of the frontal lobe (e.g., dorsolateral prefrontal cortex or DLPFC) (Biotteau 2016). The primary motor cortex (M1) is located in the dorsal part of the frontal lobe and is functionally connected to other motor areas. However, the functional connectivity between M1 and brain regions involved in motor functioning and sensorimotor processing, such as striatum and angular gyrus, may be decreased in children with DCD (McLeod 2014). Targeting such specific brain regions in rehabilitation might be effective in improving the motor outcomes of affected children.

Currently, the most beneficial interventions to improve the motor performance of children with DCD are task-oriented approaches that focus on learning a particular task rather than on the body functions required to perform a task (Smits-Engelsman 2013). A number of task-oriented approaches are commonly used to treat children with DCD (Niemeijer 2007; Polatajko 2001). The investigators believe that brain stimulation can enhance motor learning and the effect of task-oriented approaches in children with DCD. To better understand tDCS as a treatment for children with DCD, as the first step, it is critical to investigate whether tDCS can enhance motor skill learning in this population. Therefore, the investigators aim to conduct a randomized, blinded, sham-controlled interventional trial of anodal tDCS over M1 combined with a motor learning task to assess its effectiveness on motor skill learning in children with DCD. This is a pilot study to determine a sample size for a larger study.