Compromised sensitivity to relative monetary reward in Current Cocaine Addiction: evidence from the P300

Using functional magnetic resonance imaging (fMRI), we previously reported compromised neural sensitivity to monetary reward in cocaine-addicted individuals as compared to control subjects. In the current study, we sought to replicate this result using the event-related potential (ERP) recordings. Given the demonstration that the P3 waveform, previously implicated in valence processing, coded for monetary value in young healthy individuals, we currently examined this effect in 18 individuals with current cocaine use disorders (CUD) and 18 age-matched control subjects. Monetary reward (0nsub, 1nsub and 45nsub) varied across blocks of trials. Results revealed that the P3 amplitude was significantly larger for 45nsub than the 0nsub condition in the control subjects, while this gradation was absent in the CUD individuals; the behavioral results paralleled these ERP results: only the control subjects adjusted speed of response to the high as compared to the no reward condition. In addition, the CUD subjects manifested significantly faster P3 waveforms than their control counterparts; this was associated with higher self-reported excitement for the task. These current ERP results confirm our previous fMRI results and suggest a compromised neuronal sensitivity to the relative value of a secondary reward in current CUD individuals; this impairment may be translated into impulsivity or an inability to use subjective motivation to guide behavior.