Abstract:

The majority of the neuroimaging literature on drug cue reactivity has focused on subcortical and prefrontal correlates of reward, learning or executive function. However, the reactivity of sensory-motor brain regions in response to drug-associated cues (observing drug using action or drug using tool cues ) has been found to be correlated with continued drug use, craving or relapse. This action-related brain region for drug cue reactivity, which includes parietal and lateral frontal cortices, is essential for drug using behavior and relapse but it has largely been neglected as a topic of research, and little is known about the sensory and motor mechanisms of addiction. The aim of the current study was to investigate the brain reactivity of heroin dependent individuals under different cues. We hypothesized that all drug-related cues would activate the brain area associated with reward function. In addition, we hypothesized that the stimuli related to drug use action and drug use tools would activate the sensory and motor brain areas, with the two brain systems interacting simultaneously in the heroin addicted brain with regards to cue-reactivity tasks. We used a within group design to run the experiment and a block design to show the stimuli for functional magnetic resonance imagining (fMRI). Heroin abstinent and heroin dependent participants (N = 29; 17 men, 12 women; average age 42 years; right handed) were recruited through written and oral advertisements at the volunteer rehabilitation centers in Sanshui, Guangdong. 3.0-T fMRI, self-report, psychological and physiological tests for anxiety, body temperature, Galvanic skin, blood pressure, and heart rate were used to measure the cue-induced brain reactivity and body reaction while participants observed different picture cues. The cues were divided into pure drug and relevant control pictures, drug use tools and relevant control pictures, drug using action and relevant control action pictures. Compared to control cues, all drug related cues, including pure drugs, drug use tools and actions, activated ACC and HYP, which are related to the reward mechanism, and the fusiform area and lingual gyrus. When three different types of drug-related cues were compared with each other, the regions involved in the simulation of action and tool use area were found to have been activated. All the participants showed greater activity in left occipital lobe, post-central gyrus, temporal lobe, middle temporal gyrus, inferior temporal gyrus, superior parietal lobule/(SPL) and inferior parietal lobule (IPL) when viewing actions and drug use tool pictures versus pure drug pictures. Drug use action stimuli activated more sensory-motion areas than pure drug and drug use tool stimuli. These results demonstrate that drug-related cues activated two neuro systems in the brain, namely reward and sensory motor systems, at the same time. The stimuli of drug use tools and drug use action activated more sensory-motor areas. The reactivity of the sensory-motor area may indicate that heroin dependent individuals spontaneously represent the action of drug use when viewing drug-related action or tool cues. The consequence may be that it is more difficult for heroin-dependent individuals to be abstinent from drug use and more likely to relapse. The study proved the reactivity of the sensory-motor area under drug-related cues and clarified the response of different brain areas to different types of drug-related cues. The findings have significance in terms of addiction pathology and suggest that drug use actions and tool cues need be considered in the treatment of drug addiction and in relapse prevention. Also, the results indicate that drug dependent individuals need to avoid these kinds of cues in day to day life in order to prevent automatic drug use behavior.

Key words: cue-induced reactivity, reward system, sensor-motor system