Effect of add-on transcranial alternating current stimulation (tACS) on persistent delusions in schizophrenia.

The utility of non-invasive brain stimulation techniques to alleviate resistant delusions in schizophrenia is an under-researched area. In this study, we report the effectiveness of alpha transcranial alternating current stimulation (tACS) targeting the medial prefrontal cortex in ameliorating persistent delusions. Twelve Schizophrenia patients (N=12) with persistent delusions received add-on treatment with a twice-daily 20-minutes session of 10-Hz tACS. Significant reduction in severity of delusion was noted after 5th day (z=2.67, p<0.01, n=12) with further improvement after 10th day (z=2.52, p=0.01, n=9) of stimulation. Add-on treatment with 10-Hz tACS is a potential therapeutic option for treatment-resistant delusions, which requires further systematic research.

BOLD signal effects of transcranial alternating current stimulation (tACS) in the alpha range: A concurrent tACS-fMRI study.

Many studies have proven transcranial alternating current stimulation (tACS) to manipulate brain activity. Until now it is not known, however, how these manipulations in brain activity are represented in brain metabolism or how spatially specific these changes are. Alpha-tACS has been shown to enhance the amplitude of the individual alpha frequency (IAF) and a negative correlation between alpha amplitude and occipital BOLD signal was reported in numerous EEG/fMRI experiments. Thus, alpha-tACS was chosen to test the effects of tACS on the BOLD signal. A reduction thereof was expected during alpha-tACS which shows the spatial extent of tACS effects beyond modeling studies. Three groups of subjects were measured in an MRI scanner, receiving tACS at either their IAF (N=11), 1Hz (control; N=12) or sham (i.e., no stimulation - a second control; N=11) while responding to a visual vigilance task. Stimulation was administered in an interleaved pattern of tACS-on runs and tACS-free baseline periods. The BOLD signal was analyzed in response to tACS-onset during resting state and in response to seldom target stimuli. Alpha-tACS at 1.0mA reduced the task-related BOLD response to visual targets in the occipital cortex as compared to tACS-free baseline periods. The deactivation was strongest in an area where the BOLD signal was shown to correlate negatively with alpha amplitude. A direct effect of tACS on resting state BOLD signal levels could not be shown. Our findings suggest that tACS-related changes in BOLD activity occur only as a modulation of an existing BOLD response.