The purpose of this study is to better understand the neural correlates of higher-order cognition, both in the healthy brain and in schizophrenia, and to determine how these mechanisms are modulated by transcranial direct current stimulation (tDCS) at frontal and occipital scalp sites. Testing the effects of tDCS at these scalp sites on cognitive task performance will help us understand the roles of the brain regions corresponding to these sites during higher-order cognitive processing (language comprehension, cognitive control, and related attention and memory processes). Behavioral and electrophysiological (EEG) measures will be used to assess cognitive performance. The investigator's overarching hypothesis is that stimulating prefrontal circuits with tDCS can improve cognitive control performance, and ultimately performance on a range of cognitive tasks, as compared to stimulating a different cortical region (occipital cortex) or using sham stimulation. This study is solely intended as basic research in order to understand brain function in healthy individuals and individuals with schizophrenia. This study is not intended to diagnose, cure or treat schizophrenia or any other disease.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
DOUBLE
Enrollment
86
In tDCS, saline-soaked electrodes are temporary affixed to the scalp and connected to a battery-powered current generator. A weak (2 mA) constant current is then briefly applied (\~20 minutes) to stimulate the targeted brain area (e.g. the DLPFC). To control for placebo effects, the study will utilize a sham stimulation protocol that consists of very brief constant stimulation (\~1 minute). Subjects usually cannot discern the difference between the sham and experimental stimulation protocols due to habituation.
Imaging Research Center
Sacramento, California, United States
EEG Correlates of Language and Cognitive Control
Electrophysiological data recorded during completion of cognitive control and language comprehension tasks. We will measure oscillatory activity in the theta, alpha, beta and gamma frequency bands.
Time frame: Assessment will begin immediately following stimulation and last for about 1.5 hours.
Behavioral Response (Cognitive Control Task)
We will assess performance on the Dot Pattern Expectancy (DPX) task (error rates and d-prime scores).
Time frame: Assessment will begin immediately following stimulation and last for about 1.5 hours.
Behavioral Response (Language Task)
We will assess performance on a novel Language Comprehension task (accuracy and semantic relatedness judgement scores).
Time frame: Assessment will begin immediately following stimulation and last for about 1.5 hours.
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