Bilateral Prefrontal Cortex Anodal tDCS Effects on Self-reported Aggressiveness in Imprisoned Violent Offenders.

Reduced activity of the frontal lobes, and particularly of the prefrontal cortex, has been related with violent behavior, aggression and crime. The causal importance of prefrontal cortex activity for aggressive behaviors and the self-perception of aggressiveness needs however to be clarified. The aim of this study was to explore the effect of an anodal transcranial direct current stimulation protocol (tDCS, 1.5 mA, 15 min), which, according to previous studies, enhances cortical excitability, applied bilaterally over the prefrontal cortex on self-reported aggressiveness. Two imprisoned violent offender cohorts, discerned by the degree of aggressiveness (murderers vs. non-murderers), were included in this single-blind sham-controlled study. Self-reported aggressiveness was recorded before and after 3 tDCS sessions (one session per day). Four dimensions of aggression were evaluated by means of the standardized Buss-Perry Aggression Questionnaire (BAQ). In both inmate groups the results revealed an aggression-reducing effect of tDCS on the Physical aggression, Anger, and Verbal aggression dimensions of the BAQ. In the Hostility dimension, tDCS significantly reduced aggression only in the group of murderers. These results suggest that modulation of prefrontal cortex excitability by 3 consecutive sessions of tDCS reduces self-reported aggressiveness similarly in murderer and non-murderer samples.

Poststimulation time interval-dependent effects of motor cortex anodal tDCS on reaction-time task performance.

Anodal transcranial direct current stimulation (tDCS) induces long-term potentiation-like plasticity, which is associated with long-lasting effects on different cognitive, emotional, and motor performances. Specifically, tDCS applied over the motor cortex is considered to improve reaction time in simple and complex tasks. The timing of tDCS relative to task performance could determine the efficacy of tDCS to modulate performance. The aim of this study was to compare the effects of a single session of anodal tDCS (1.5 mA, for 15 min) applied over the left primary motor cortex (M1) versus sham stimulation on performance of a go/no-go simple reaction-time task carried out at three different time points after tDCS-namely, 0, 30, or 60 min after stimulation. Performance zero min after anodal tDCS was improved during the whole course of the task. Performance 30 min after anodal tDCS was improved only in the last block of the reaction-time task. Performance 60 min after anodal tDCS was not significantly different throughout the entire task. These findings suggest that the motor cortex excitability changes induced by tDCS can improve motor responses, and these effects critically depend on the time interval between stimulation and task performance.