PORTLAND, ORE. – Combining transcranial direct current stimulation and cognitive training resulted in an improvement in a greater number of cognitive outcomes than either intervention alone in a small, randomized, controlled trial of patients with Parkinson’s disease and mild cognitive impairment.
Researchers at Curtin University in Perth, Western Australia, conducted the trial comparing the effects of standard (not individualized) cognitive training (SCT), tailored (individualized) cognitive training (TCT), transcranial direct current stimulation (tDCS), and a combination of tDCS with either form of cognitive training on cognitive outcomes, activities of daily living, and quality of life in such Parkinson’s patients with mild cognitive impairment. Previously, it was not known whether either form of cognitive training or tDCS or a combination of the two would be most efficacious in improving cognition in such patients.
Patients had cognitive deficits that did not interfere with functional independence and were responding to stable doses of antiparkinsonian medication. Forty-two eligible participants underwent neuropsychological testing at baseline and were randomly and equally assigned to one of six groups: SCT, TCT, tDCS, SCT+tDCS, TCT+tDCS, or control.
Cognitive training consisted of three 45-minute sessions per week for 4 weeks using Smartbrain Pro software in participants’ homes. tDCS involved constant 1.5 mA stimulation for 20 minutes in one session per week for 4 weeks at the university, with the anode placed over area F3 to stimulate the left dorsal lateral prefrontal cortex. Follow-up evaluations were at 12 weeks.
The following tests were used to evaluate each outcome: executive function – Stockings of Cambridge; attention/working memory – Stroop test; memory – paragraph recall; quality of life – PDQ-39; activities of daily living – Unified Parkinson’s Disease Rating Scale-II; and language – similarities test.
In general, combining tDCS with either form of cognitive training resulted in significantly greater improvements in more outcomes than any of the modalities alone. SCT showed positive results when compared against the control group in memory improvement at follow-up (effect size, 1.30), as well as quality of life and activities of daily living postintervention (effect sizes, 0.24 and 0.33, respectively). TCT showed benefits on quality of life at both time points (effect sizes 0.26 at postintervention and 0.12 at follow-up, respectively).
When combined with tDCS, SCT produced improvements in attention/working memory both postintervention and at 12-week follow-up (effect sizes, 0.60 and 0.24, respectively) as well as executive function at postintervention and follow-up (0.41 and 0.23). Improvement in activities of daily living and language were statistically significant only immediately postintervention.
Combining tDCS with TCT resulted in improvements postintervention and at follow-up on measures of memory (1.36 and 1.75) and executive function (0.19 and 0.92), as well as in language postintervention (1.06).
“The main takeaway was that the groups that completed both cognitive training and brain stimulation improved to a greater extent and in more outcomes than the groups that just completed the brain training or the stimulation individually,” Mr. Lawrence said. “The majority of the effects were shown immediately after the intervention, but some of the promising results ... actually maintained improvement at the 12-week follow-up, so that was after about 8 weeks, when they didn’t complete any intervention whatsoever.”
The improvements are probably clinically meaningful to patients since they themselves reported the outcomes on quality of life and activities of daily living scales, he said. He added that studies are coming out that look at the effect of brain stimulation and brain training at the same time, and they have shown improvement, but not many such studies have yet been done in Parkinson’s disease.