Cognitive Training After Stroke : Effects and Mechanisms

Stroke is a major cause of severe cognitive and physical disability. Despite the high and increasing incidence, and large health, economic, social and personal consequences, studies designed to remedy cognitive impairments and improve rehabilitation care following stroke are lacking. A promising line of research have shown that weak electrical current (tDCS) can be a safe, cost-effective, and potent treatment when combined with other rehablitational approaches. The underlying mechanism is assumed that tDCS facilitates neuronal signaling, improving plasticity and facilitating rehablitational outcome. But further research is needed to better understand the mechanisms at hand, and to better evaluate the potential clinical utility. The scope for the current project is to investigate both cognitive and neuronal effects of tDCS in combination with cognitive training , with the ultimate goal to improve current rehabilitational healthcare. To achieve this we will use multimodal MRI, EEG, and a comprehensive battery of neuropsychological asessment, to describe and evaluate the effect of tDCS in rehabilitation purposes.

Participants are randomly assigned to either active or sham condition, using codes provided by the manufacturer and implemented by an in-house Matlab script, pseudo-randomizing participants while maintaining balance in groups of 20. tDCS stimulation is applied at six occasions for each participant, with a minimum of 48 hours between stimulations, aiming at an average of two stimulations per week. Stimulation current is1000 μA, stimulation time was 20 min for the active group with a ramp-up time of 120 s and fade-out time of 30 s. The current intensity is limited to 1 mA to limit the risk of adverse events due to the electrical stimulation. The sham stimulation consists of ramp-up followed by 40 s of active stimulation and then fade-out, following factory settings. Cognitive training will be done by the computerized working memory training program (Cogmed Systems AB, Stockholm, Sweden) consisting of 25 online training sessions. In this study, to increase feasibility, we utilize 17 sessions over a period of three to four weeks, corresponding to approximately five weekly training sessions. On average, we aim at two training sessions combined with tDCS per week with a minimum of one day between each tDCS session. The remaining CCT sessions are performed at home. Neuropsychological assessments and MRI assessments are conducted three times: at baseline 1, after a waiting period of 2-4 weeks (baseline 2, before intervention) and immediately post intervention. Self-reported symptoms of fatigue and depression are assessed at five time points, before, during and after completing intervention.

Participants recieving active trancranial direct current stimulation (tDCS) Parameters: 20 minutes anodal tDCS 1mA. Two times a week, for three weeks. Anode placed at F3, cathode placed at right cerebellum.

Participants recieving passive / sham trancranial direct current stimulation (tDCS) Two times a week, for three weeks. Anode placed at F3, cathode placed at right cerebellum.

Evidence of change in neural activity in attentional-related brain areas after receiving anodal tDCS, as measured with functional MRI

Change in activation patterns during multiple object tracking (MOT) at first baseline, before initiating training (second baseline, on average 4 weeks after baseline measure), and after a three-week intervention (post-intervention assessment)

Fatigue Severity Scale (FSS), a seven-point Likert scale on subjective fatigue severity/impact. 9 items scored from 1 (less symptoms) to 7 (most severe symptoms). Scores are reported as mean scores, lowest possible mean = 1, highest possible mean = 7.

Patient Health Questionnaire (PHQ-9), self-reported depressive symptoms. Scale consists of 9 items, scored from 0 (not at all) to 3 (nearly every day). Scores are reported as sum scores, range 0 (less symptoms) - 27 (more symptoms)

Inclusion Criteria: - MR/CT revealing ischemic or hemorrhagic damage (stroke). Exclusion Criteria: History of illness or damage to the CNS, besides stroke. <18 years of age Extensive cognitive decline or dementia Severe psychiatric disorders Substance or alcohol abuse Contraindications for MRI.