The Effect of Repeated Transcranial Direct Current Stimulation of the Prefrontal Cortex on Antisocial and Aggressive Behavior
Phase: NA
Conditions: Antisocial Behavior, Aggression
Sponsor: University of Pennsylvania

 
 
 
 
 
 
 
 
 
 
 
The Effect of Repeated Prefrontal Cortex Stimulation on Antisocial and Aggressive Behavior 
 
NCT02674516 
 
January 7, 2022 
 
  
 
 
 

Study Protocol 
The objective of this study is to test whether stimulating the prefrontal cortex using 
transcranial direct current stimulation (tDCS) reduces aggressive behavior.  
 
tDCS Intervention 
tDCS was administered by trained study personnel using a battery-driven, constant-
current stimulator (TCT Research) during three lab visits on three consecutive days. Two anodal 
electrodes were placed over the DLPFC bilaterally (F3 and F4) according to the International 10-
20 EEG system. A constant current of 2mA (1mA to each DLPFC site) was applied for 20 
minutes through saline-soaked sponge electrodes (5x5cm). A single extracephalic cathodal 
electrode (5x7cm) was placed at the posterior base of the neck in order to minimize unintentional 
effects of inhibitory stimulation on brain activity.  
Following standard tDCS protocol, stimulation commenced after a 30-second ramp-up 
period. The current was ramped down over the last 2 seconds. The tasks performed during tDCS 
are understood to influence the behavioral after-effects of stimulation (Gill et al., 2015). Thus, 
during the stimulation session, all participants performed the Psychology Experiment Building 
Language (Mueller and Piper, 2014) version of two cognitive tasks that are known to engage the 
DLPFC, the Psychomotor Vigilance Task (Dinges and Powell, 1985; Cui et al., 2015), followed 
by the Iowa Gambling Task (Bechara et al., 1994; Ernst et al., 2002). Although participants in 
both intervention arms received the same electrode placement and ramp-up/down times, 
stimulation for the sham control group was discontinued after 30 seconds. This has proven to be 
effective for blinding as participants habituate to the sensation of stimulation within seconds of 
current initiation (Gandiga et al., 2006).  

 
Blinding 
Participants and experimenters were blind to the tDCS condition assignment. The trial 
adhered to established procedures to maintain separation between staff that conducted the 
stimulation and staff that engaged with the participant. In each experimental session, only one 
experimenter who set up the tDCS procedure had knowledge of the participant’s allocation. To 
further ensure blinding, all participants were kept blind to the objective of the study and outcome 
measures were not taken in the presence of research staff as they could lead to biased results.  
 
Aggression 
The voodoo doll task is a reliable and validated behavioral analog measure of aggression 
(DeWall et al., 2013). In this task, participants were shown a computer-based image of a doll that 
represented a partner or a close friend. They were told that they were given the opportunity to 
release their negative energy to that individual by inserting as many pins (0-51) in the doll as 
they wished. Instructions did not use the word “voodoo”. Stabbing the doll with more pins 
indicated higher levels of aggression.  
 
Statistical Analysis 
One-way ANCOVA was used to test group differences in aggression. Baseline measures 
were examined as possible covariates: variety of crime throughout the lifetime, aggression, GPA, 
trait anxiety, social adversity, psychopathy, the lack of premeditation and sensation-seeking 
dimensions of impulsivity, and self-control. 
 

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