Two new neurophysiological indices of cocaine craving: evoked brain potentials and cue modulated startle reflex

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Abstract
Craving for cocaine is one of the hallmarks of cocaine dependence. One of the problems with craving is its measurement. Traditional psychophysiological indices such as skin conductance and heart rate have yielded contradictory results. These measures of craving were found to correlate only moderately with self-reported craving. In the present study, event-related brain potentials (ERPs) and the cue modulated startle response (CMSR) are evaluated as indices for cocaine craving. Twenty-one abstinent cocaine-dependent subjects were divided into high and low cravers group based on the median split of self-reported craving scores. ERPs and CMSR were measured when subjects watched neutral, pleasant, unpleasant and cocaine-related pictures. Overall, it was found that cocaine-dependent subjects showed augmented slow-positive waves (SPWs) of the ERP on the cocaine pictures compared to neutral pictures. Only high cravers showed larger SPWs on the cocaine cues, suggesting an association between cue-elicited SPWs and self-reported cocaine craving. By contrast to the ERP measures, CMSR did not differentiate between cocaine pictures and neutral pictures. In addition, no differences between the low- and high cravers on the CMSR measure were found. The present results show that the evoked-potentials paradigm provides promising results to index cue-elicited craving. The use of startle modulation deserves further investigation.