Stimulating cognition in schizophrenia: A controlled pilot study of the effects of prefrontal transcranial direct current stimulation upon memory and learning

- Individuals with schizophrenia commonly have cognitive impairments, which predict longer-term functional outcomes.
- The key dysfunctional domains are memory and learning.
- Combining transcranial direct current stimulation (tDCS) and cognitive training (utilising both working memory (WM) and implicit learning (IL) tasks), improves cognitive deficits in patients with schizophrenia.
- This is the first study to show a significant longer-term effect of tDCS on WM in schizophrenia.
- tDCS may offer an important approach to ameliorate cognitive deficits in schizophrenia.

BackgroundSchizophrenia is characterized by prominent cognitive deficits, impacting on memory and learning; these are strongly associated with the prefrontal cortex.Objective/hypothesisTo combine two interventions, transcranial direct current stimulation (tDCS) over the prefrontal cortex and cognitive training, to examine change in cognitive performance in patients with schizophrenia.MethodsA double blind, sham-controlled pilot study of 49 patients with schizophrenia, randomized into real or sham tDCS stimulation groups. Subjects participated in 4 days of cognitive training (days 1, 2, 14, 56) with tDCS applied at day-1 and day-14. The primary outcome measure was change in accuracy on working memory and implicit learning tasks from baseline. The secondary outcome measure was the generalization of learning to non-trained task, indexed by the CogState neuropsychological battery. Data analysis was conducted using multilevel modelling and multiple regressions.Results24 participants were randomized to real tDCS and 25 to sham. The working memory task demonstrated a significant mean difference in performance in the tDCS treatment group: at day-2 (b = 0.68, CI 0.14-1.21; p = 0.044) and at day-56 (b = 0.71, 0.16-1.26; p = 0.044). There were no significant effects of tDCS on implicit learning. Trend evidence of generalization onto untrained tasks of attention and vigilance task (b = 0.40, 0.43-0.77; p = 0.058) was found.ConclusionsThis is the first study to show a significant longer-term effect of tDCS on working memory in schizophrenia. Given the current lack of effective therapies for cognitive deficits, tDCS may offer an important novel approach to modulating brain networks to ameliorate cognitive deficits in schizophrenia.