A randomised control trial of cognitive training and non-invasive brain stimulation in Parkinson's: The impact on cognition (thinking skills) and quality of life.

This study will use a dual-protocol intervention combining cognitive training and transcranial direct current stimulation (tDCS). These two interventions will be conducted simultaneously in each session. Upon study entry, participants will be assigned to one of the following 4 groups: 1. Anodal (active) tDCS and cognitive training (active) 2. Sham (control) tDCS and cognitive training (active) 3. Anodal (active) tDCS and placebo (control) cognitive training 4. Sham (control) tDCS and placebo (control) cognitive training. ARM 1 - Active Cognitive Training Participants in the active cognitive training groups (1 and 2) will complete cognitive training. Cognitive training will be conducted using MyBrainTrainerTM, a commercially available cognitive training package that runs via an online website. Participants will complete two 20-minute intervention sessions per week for 4-weeks (a total of 8 sessions). Jean, Bergeron, Thivierge, and Simard (2010) suggest that for people with MCI, 5 to 15 cognitive training sessions completed in less than 12 weeks are equally efficacious as longer and more costly interventions. In our experience, participants are likely to demonstrate fatigue after approximately 30 minutes of cognitive training which may impact their performance, hence the restricted duration of the intervention. Participants will complete a predetermined cognitive training program comprising five different exercises. These activities will include one short-term memory exercise, one executive function exercise, one information processing exercise, one working memory exercise, and one visual spatial exercise. Each exercise lasts approximately 3 – 4 minutes (depending on speed of response) and has a function for demonstration of the exercise before commencement. The program will halt after 20 minutes of training. In week one, participants will complete 2 identical training sessions comprising the 5 exercises at beginner’s level (sessions 1 and 2). In weeks 2 and 3, participants will complete 4 identical training sessions comprising the 5 exercises at intermediate level (sessions 3, 4, 5, and 6). In week 4, will complete 2 identical training sessions comprising the 5 exercises at advanced level (sessions 7 and 8) Online feedback (i.e. during the trials) will not be provided to the participant for any of the exercises, as this will help to reduce the risk of any distress associated with performance. Participants’ performance will be automatically monitored and recorded by the program, giving us an indication of the effectiveness of the training for each participant. For all exercises in all sessions, the researcher will provide verbal instructions and an example trial to demonstrate the task. Before commencing each exercise, the researcher will ask the participant if they understand the task and will give the participant an opportunity to ask questions about the instructions and, if required, demonstrate the task again. The program also provides written instructions on the screen just prior to commencement of the exercise. This intervention will be delivered by the project research assistant who has over 5 years experience with working in Parkinson's intervention trials. The research assistant is a psychology graduate. The intervention will be provided face-to-face and individually. ARM 2 - Active tDCS Participants in the active tDCS groups (the anodal (active) groups 1 and 3) will receive 20 minutes of constant current 1.5 mA (equivalent to 0.08 mA/cm2). Stimulation over the left dorsal lateral prefrontal cortex (DLPFC). This level is consistent with safety guidelines (Nitsche et al., 2008) and is well tolerated in those with PD-MCI (Lawrence et al., 2018). tDCS will be delivered by a constant current stimulator (Soterix®), which is administered using two 35 cm 2 sponge electrodes that have been soaked in saline solution. The anode electrode will be placed over F3 according to the 10-20 international system for EEG electrode placement, to stimulate the left DLPFC. The cathode (neutral) electrode will be position on the left side of the forehead. There will be a period of 30 seconds at the beginning and end of the tDCS for ramp up/down. tDCS will be delivered at the same time the participant is completing the cognitive training such that tDCS and cognitive training occur simultaneously for 20 minutes. This intervention will be administered by the project research assistant (as above) who is fully trained on the the set-up and administration of tDCS, and has previously completed a similar study as part of her Phd. The intervention will be delivered face-to-face and individually.