Cognitive Training and Brain Stimulation in Parkinson's Disease

Participants will be invited to attend the Neurosciences Laboratory at the School of Psychology, Curtin University to complete a pre-intervention neuropsychological assessment. Upon arrival the researcher will give participants an overview of the present study, clarify doubts and answer questions that participants may have. The researcher will ask participants to carefully read through the information sheet and consent form. Upon receipt of informed consent, participants will be asked to complete 14 different neuropsychological tests assessing cognitive functioning, activities of daily living (ADL), and quality of life (QOL). Thirteen tests are paper/pencil based and one test, Stockings of Cambridge, will be completed on the Cambridge Automated Neuropsychological Test and Assessment Battery (CANTAB). The CANTAB is a touch screen tablet computer comprising a range of established neuropsychological tests. All tests have been appropriately selected and recommended for use in Parkinson's Disease (PD; see Litvan et al., 2012). Prior to each test participants will be given oral instructions outlining how to complete the test. Participants will be offered regular breaks during assessments. If a participant is showing signs of fatigue or distress and they choose to continue, they will be offered additional breaks to assist them in completing the tasks. However, due to possible learning effects participants will be unable to complete a re-test if they choose to stop an assessment. At completion participants will be thanked for their participation with a $10 gift card. Each participant’s assessment results will be appropriately scored and interpreted and those who meet the inclusion criteria (presence of Mild Cognitive Impairment) will be asked to participate in the next stage of the project. After 90 participants have completed pre-intervention neuropsychological assessments and met the necessary inclusion criteria and transcranial direct current stimuluation (tDCS) exclusion criteria they will be asked to read an information sheet and sign a consent form for this stage of the project. Then participants will be randomised to one of six intervention groups: (1) standard cognitive training, (2) tailored cognitive training, (3) tDCS, (4) standard cognitive training + tDCS, (5) tailored cognitive training + tDCS, or (6) control. Standard cognitive training involves a set of cognitive tasks administered to participants regardless of their individually different cognitive deficits. Whereas tailored cognitive training is customised to address specific cognitive impairments of the individual (e.g., memory, language, executive functions). Participants allocated to the cognitive training groups will complete three 45-minute sessions of in-home computer-based cognitive training per week for 4-weeks. Cognitive training will be competed using the Smartbrain Pro program (www.smartbrain.com) and streamed via Optus Mini Wifi modems onto Pendo Pad tablets. During the first week the researcher will visit participants to set up the equipment, teach them how to use the program, answer questions, and ensure they are able to complete the activities. From weeks two to four the researcher will make follow-up telephone calls to ensure participants are complying with the training and assist them with any issues they may be experiencing. Participants allocated to the groups completing tDCS will complete 4-sessions of tDCS over 4-weeks (1-session per week). tDCS sessions will be delivered by a constant current stimulator (Empi) and involve 30 minutes of constant current 2mA stimulation (equivalent to 0.08 Ma/CM2) over their left dorsal lateral prefrontal cortex, administered with two 35 cm2 sponge electrodes soaked in saline solution. To stimulate the left dorsal lateral prefrontal cortex, the anode electrode will be placed over F3 according to the 10–20 international system for EEG electrodes placement. There will be a period of 30 seconds at the start and end of tDCS for ramp up/ramp down. Participants will relax (read a magazine, have a cup of tea) during each tDCS session. Participants allocated to the cognitive training + tDCS groups will complete the previously described activities simultaneously for 4-weeks. At completion of the 4-week cognitive training and tDCS interventions, participants will complete the same neuropsychological tests (as pre-intervention) at post-intervention and 3-month follow-up. Participants may experience cognitive fatigue during neuropsychological assessments and cognitive training. However, regular breaks will be offered during assessments and Smartbrain Pro creators recommend no more than 45-minutes of cognitive training to reduce the likelihood of fatigue. The use of tDCS in the present study involves a single 9-volt battery to apply a constant current (usually one millivolt) for a set period of time (30 minutes). The current is passed through rubber electrodes (6 cm x 4 cm) placed inside sponge containers moistened with water. The use of large electrodes (with an area of 24 cm2) ensures that current density is well below levels that might be perceived as unpleasant or painful. The density of 0.08 mA/cm2 is in the lower range of that used in the research studies published to date (Boggio et al., 2006; Nitsche et al., 2008). Participants might experience a tingling sensation under an electrode at the onset of stimulation but this sensation quickly fades. The procedure is safe, and no significant adverse events have been reported with low current densities (from 0.03 to 0.08 mA/cm2). The stimulation in the proposed research will be applied for 30 minutes (during which no task is required of the participant) with a current density of 0.08 mA/cm2. Stimulation can cause a feeling of nausea if one of the electrodes is positioned over a mastoid process (the bony prominence behind the ear). This location, which can activate the vestibular system (the organ of balance), will be avoided in this project. The safety of tDCS is discussed by Nitsche et al. (2008) and the tDCS protocol to be used in this study adheres to all safety recommendations. The researchers will adhere to a strict administration and adverse event protocols. The researchers will ask participants how they are feeling during the tDCS phase and will remain with the participant at all times. The researchers will be first-aid trained to cope with any (unlikely) issues and the laboratory has a telephone. If at any point the participant experiences any adverse effects during neuropsychological assessments, cognitive training, or tDCS, the procedures will cease. All assessments and interventions will be completed when participants are in 'ON' stage of medication use (approximately 1-hour post medication) to ensure they are feeling their best. At completion of follow-up assessments participants will be given a $15 gift card to thank them for participating in the research.