Transcranial direct current stimulation combined with cognitive training improves two executive functions: Cognitive flexibility and information updating after traumatic brain injury

Traumatic brain injury (TBI) often causes persistent deficits in cognitive flexibility and information updating. Cognitive flexibility refers to the brain's ability to adjust its thinking and behavior in response to changing circumstances, whereas information updating is the process of incorporating new facts into current knowledge. Both cognitive flexibility and information updating are critical components of executive function, and their impairment can have a major influence on a person's capacity to operate independently and adjust to life's problems following a TBI. Understanding and addressing these specific cognitive processes is therefore critical in designing successful therapies for TBI patients. Previous studies have examined the effects of non-invasive brain stimulation and cognitive training separately. This study investigated the effects of combining transcranial direct current stimulation (tDCS) with computer-based cognitive training, comparing this combined intervention against a control group with no treatment, to assess improvements in two executive functions in TBI patients: cognitive flexibility and information updating. Thirty TBI patients, 2-12 weeks post-injury with impaired executive dysfunction, were randomized to an experimental or control group. The experimental group received ten 30-minute sessions over 2 weeks of anodal (A-tDCS), 2.0 mA to the prefrontal cortex while performing cognitive training tasks from the RehaCom software. The control group received no intervention during this period. Cognitive flexibility and information updating were assessed before and after the intervention period using the n-back working memory task, Wisconsin Sorting Card Test, and quantitative electroencephalography (qEEG) during eyes-closed state. Statistically significant differences in theta, alpha, beta, and gamma band power were observed between groups (p < .05, 4 < f < 6). Secondary outcomes indicated significant improvements in cognitive flexibility within Wisconsin Card Sorting Test and information updating performance within n-back task (p < .05, 7 < f < 20). The combination of tDCS and cognitive training may improve cognitive flexibility and information updating in TBI patients by enhancing plasticity and connectivity in prefrontal regions involved in these complex cognitive processes.