The purpose of this study is to investigate different stimulation intensities and frequencies of transcranial direct and alternating current stimulation over the dorsolateral prefrontal cortex for cognitive improvement in schizophrenia.
In this randomized, double-blind study, 50 patients diagnosed with schizophrenia are randomly assigned into two arms. The first group receives transcranial direct current stimulation (tDCS) at three intensities (2 mA, 3 mA, and sham) and the second group receives transcranial alternating current stimulation (tACS) at three different frequencies (8 Hz, 40 Hz, and sham) over the left dorsolateral prefrontal cortex for 20 min. There are at least 72 hours between stimulation sessions. The patients conduct three cognitive tasks from the CANTAB neuropsychological battery for schizophrenia during stimulation including a working memory task, a cognitive flexibility task, and an emotion recognition task. Mood stability is also evaluated before and after each stimulation session with the Positive and Negative Affect Scale (PANAS).
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
TRIPLE
Enrollment
50
In tDCS, direct electrical currents at the intensity of interest (2 mA for example) are generated by an electrical stimulator and are noninvasively delivered to the scalp through a pair of saline-soaked sponge electrodes (7×5 cm).
In tACS, alternating electrical currents at the frequency of interest (8 Hz for example) are generated by an electrical stimulator and are noninvasively delivered to the scalp through a pair of saline-soaked sponge electrodes (7×5 cm).
Ardabil University of Medical Sciences
Ardabil, Iran
Spatial Working Memory behavioral performance
The test begins with a number of coloured squares (boxes) shown on the screen. The aim of this test is that by selecting the boxes and using a process of elimination, the participant should find one yellow 'token' in each of a number of boxes and use them to fill up an empty column on the right-hand side of the screen.
Time frame: During procedure (4 minutes)
executive function behavioral performance
The participant is shown two displays containing three coloured balls. The test administrator first demonstrates to the participant how to move the balls in the lower display to copy the pattern in the upper display and completes one demonstration problem, where the solution requires one move. The participant must then complete three further problems, one each requiring two moves, three moves and four moves. Next the participant is shown further problems and must work out in their head how many moves the solutions require and then select the appropriate box at the bottom of the screen to indicate their response
Time frame: During procedure (8-10 minutes)
Emotional recognition behavioral performance
Computer-morphed images derived from the facial features of real individuals, each showing a specific emotion, are displayed on the screen, one at a time. Each face is displayed for 200 milliseconds and then immediately covered up to prevent residual processing of the image. The participant must select which emotion the face displayed from 6 options (sadness, happiness, fear, anger, disgust or surprise)
Time frame: During procedure (60 minutes)
The Positive and Negative Affect Schedule (PANAS)
The Positive and Negative Affect Schedule (PANAS) is a self-report questionnaire that consists of two 10-item scales to measure both positive and negative affect. Each item is rated on a 5-point scale of 1 (not at all) to 5 (very much).
Time frame: through study completion in each experimental session up to 1 hour
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