Investigation of the effects of the transcranial direct current stimulation on eyewitness testimony and executive functions

The present study investigated the effects of transcranial direct current stimulation (tDCS) on the accuracy of eyewitness memory and executive functions. Executive functions were studied in the context of hot and cold systems. Risk-taking behavior was investigated as hot cognition, whereas attention, response time, set-shifting, inhibitory control, and verbal and visuospatial working memory were investigated as cold executive functions. 83 university students (59 female, 24 male) participated in the double-blind sham-controlled study. Participants were randomly assigned to eight different tDCS conditions. Five of these groups were given prefrontal cortex stimulation, including one sham; the other three groups were given anterior temporal lobe stimulation, including one sham. TDCS was applied with an offline protocol at 2 mA intensity for 20 minutes. Immediately after the stimulation, the participants watched a robbery video. Following the video, recall and recognition tests were administered. Then, a computer task assessing risk-taking and verbal and nonverbal cognitive tests were administered. The results indicated that anodal stimulation of the left dorsolateral prefrontal cortex (DLPFC) improved recall in eyewitness memory by reducing omission errors. As expected, cathodal stimulation of the left DLPFC decreased eyewitness memory performance compared with anodal and sham groups. Non-significant trends suggest that risk-taking behavior can be altered by anodal and cathodal stimulation of the left DLPFC. The conflicting results that emerged in the modulation of cold executive functions with tDCS were discussed, and the findings were explained in line with the tDCS literature. Although it is observed that a single session of tDCS can improve eyewitness memory performance, studies with larger samples are needed to better understand state dependency and the effects of tDCS' polarity.