Extended High Definition Transcranial Direct Current Stimulus for Improvement in Cognitive Functions as Measured by...

Cognitive symptoms form core of schizophrenia affecting interpersonal and socio-occupational functioning. Impaired dorsolateral prefrontal cortex function is implicated in these symptoms. Dysfunction in sensory-motor network (SMN) has been attributed to cognitive dysfunction in schizophrenia. High-definition tDCS (HD-tDCS), an optimized form of tDCS, has the potential for more focalized neuromodulation. Extended HD-tDCS (eHD-tDCS), that is, more than 10 sessions over an extended period of time, may increase the effectiveness of stimulation.

We aimed to study the effects of eHD-tDCS on SMN alterations for improvement in cognitive functions in chronic schizophrenia.

Fifty-one patients of chronic schizophrenia (>2-year continuous illness) with predominantly cognitive symptoms were enrolled for this sham-controlled trial. Participants received 20 sessions of eHD-tDCS at 2 mA for 20 minutes twice daily over 10 days. Montreal Cognitive Assessment Scale and Clinical Global Impression-Severity Scale and Resting State f MRI (rsfMRI) were used to assess outcome. Clinical assessments were carried out at baseline, 2 weeks, and 6 weeks and rsfMRI at baseline and 2 weeks.

Significant improvement was noted in both active and sham groups across all outcome variables over time. However, a statistically significant decrease in cognitive symptoms and illness severity in active group was noted at the end of treatment at 2 weeks, maintained till the end of 6 weeks. After application of eHD-tDCS, a significant improvement in functional connectivity was noted in SMN. The novel extended stimulation protocol was safe and well tolerated.

Extended HD-tDCS emerges to have a substantial potential in the treatment of cognitive symptoms and it is safe and well tolerated.