Use of the P300 event-related potential component to index transcranial direct current stimulation effects in drug users.

Drug use causes significant social and financial problems and these are exacerbated by difficulties in stopping use and subsequent maintenance of abstinence. There is also difficulty in identifying the beneficial treatment for an individual, made more problematic given the high drop-out rates in treatment programs. Here, the effects of transcranial direct current stimulation (tDCS) on the amplitude of the P300 event-related potential component, previously suggested to be indicative of successful remission, was measured in recently abstinent amphetamine users. This component was collected during a Posner cuing task which was presented to this group and to control (non-user) participants, using task cues of neutral and drug-related images. The abstinent drug users were divided into two groups, one of which received tDCS daily for five days, with the cathode over the left dorsolateral prefrontal cortex (DLPFC) and the anode over the right DLPFC, and one receiving sham stimulation over the same time period. Behavioral performance and P300 amplitudes were measured before and after the period of tDCS delivery. Control participants were tested with the same time-schedule of task presentation but without administration of tDCS. Drug users initially showed a larger cost of invalid cues on task performance compared to control (non-drug user) participants and this was reduced following delivery of tDCS. Additionally, tDCS resulted in increased amplitude of the P300 component, significantly so for neutral cues, with the resulting pattern being more similar to that of the non-users. This provides a good basis for further investigation of both the utility of tDCS in modulation of cognition in addict groups, and to investigate the effects of modulating the P300 component on remission rates, a relationship that seems to be the case for this measure without use of tDCS modulation. Importantly, this study also provides a further addiction group showing P300 amplitude modulation as a result of tDCS administration.