Potential Delayed Positive Effects of tDCS on Improving Introspective Accuracy in Social Cognition in Schizophrenia

Impairments in introspective accuracy (IA) are prominent among schizophrenia patients and detrimentally affect daily functioning, making IA a potential therapeutic target. Recent research highlights the role of the right rostrolateral prefrontal cortex (rlPFC) in IA and suggests that transcranial direct current stimulation (tDCS) to this region may improve it. Therefore, we tested whether applying tDCS to the right rlPFC could enhance IA for schizophrenia patients and explored the potential order/delayed effects.

A randomized, double-blind, sham-controlled crossover design was used. Patients with a schizophrenia spectrum disorder (N = 40) underwent 2 tDCS sessions targeting right rlPFC (one was active stimulation and the other was sham) about a week apart. After each session, participants completed executive function and emotion recognition tasks for evaluating IA.

When ignoring order effects, tDCS did not affect performance, IA, or confidence ratings across 3 tasks, except for increased confidence ratings in the cognitive task after active stimulation versus sham. However, considering order effects revealed significant interaction effects between condition and order for both task performance and IA. The group receiving active stimulation at visit 1 (Active First) generally improved over time in both cognitive and social cognitive task performance and in social cognitive IA, specifically for emotion recognition ability. In contrast, the group receiving sham stimulation at visit 1 (Sham First) showed no change in performance or IA over time.

Our findings provide preliminary evidence for potential positive, but delayed, effects of tDCS in improving task performance and IA in schizophrenia.