This study proposes to assess the effect of trans-cranial direct current stimulation (tDCS) on cognitive control, working memory, functional, clinical, and cognitive outcomes in schizophrenia patients.
Cognitive functions and EEG correlates will be thoroughly assessed in schizophrenia patients undergoing a tDCS treatment and compared with patients receiving a placebo stimulation. The treatment will involve 20 minutes of tDCS application to the left prefrontal and temporo-parietal cortex, twice a day for five days, a procedure shown to be effective in improving other symptoms of psychosis such as negative symptoms and hallucinations. Critically, in addition to standard neuropsychological testing, cognitive assessments will involve tasks that tap cognitive control and working memory, impairments in which comprise two of the core cognitive disturbances in schizophrenia and which have been linked to brain rhythm disturbances measurable by EEG recordings. Investigators will also assess changes in functional outcome by tDCS and investigate relationships between improvements in cognition, brain rhythms and functional outcome. All these assessments will occur just prior to tDCS application, just after completion of the tDCS series, and then again at 2 months follow-up. There will be two separate independent groups of patients who will be randomized to active versus sham treatments. The first group will have early course schizophrenia (less than 5 years of antipsychotic treatment; n=40). The second group will be chronic schizophrenia (greater than 5 years of antipsychotic treatment; n=40). Relevance This proposal would be the first integrated study of the effects of tDCS on cognitive symptoms, brain function and functional outcome in schizophrenia. A positive outcome would represent a marked improvement in clinical therapeutics for cognition in psychosis and provide a powerful tool for improving functional outcome in this debilitating disorder. Understanding the impact on brain rhythm disturbances could support the study of similar stimulation-based therapeutic approaches to other neuropsychiatric disorders that shows similar disturbances in cognition and brain rhythms activity, such as bipolar disorder and autism.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
TRIPLE
Enrollment
17
Active stimulation group will receive 20 min of 2 mA direct current stimulation.
This will be an active sham involving brief (15 msec) low current (0.11 mA) pulses every 550 ms.
Baylor College of Medicine
Houston, Texas, United States
Cognitive Control
The investigators will assess cognitive control using the Preparing to Overcome Prepotency (POP) task. The accuracy mean differences between the high and low control conditions will be used as dependent measures. The study is powered at 0.8 to observe a post-pre treatment improvement in cognitive control with a substantial effect size (d=0.56) compared to sham stimulation with effects relatively stable measured 2 months after baseline. The hypothesized effect size will be d=0.60.
Time frame: Week 1
Working Memory
The investigators will assess working memory using a working memory task. The accuracy mean differences between the high and low control conditions will be used as dependent measures. The study is powered at 0.8 to observe a post-pre treatment improvement in cognitive control with a substantial effect size (d=0.56) compared to sham stimulation with effects relatively stable measured 2 months after baseline. The hypothesized effect size will be d=0.60.
Time frame: Week 1
Negative Symptoms
A secondary outcome measure is the severity of negative symptoms as quantified by Scale for the Assessment of Negative Symptoms (SANS). This study is powered at 0.8 to observe a post-pre treatment improvement in negative symptoms with a moderate effect size (d=0.56) compared to sham stimulation with effects relatively stable measured 2 months after baseline. The hypothesized effect size will be d=0.60.
Time frame: Week 1
Auditory Hallucinations
A secondary outcome measure is the change over time in the severity of auditory hallucinations as assessed by the Auditory Hallucination Rating Scale (AHRS). In a study conducted using a similar montage and current strength (Brunelin et. al 2012), a reduction in auditory hallucinations with a substantial effect size (d=1.58) was observed in 30 patients with schizophrenia. However, as their study recruited only those patients with severe hallucinations while the current study does not have such an inclusion criterion. The investigators expect a more modest effect size of d=0.60.
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Time frame: Week 1