Exploring Neural Network Of The Anterior Cingulated Cortex In Heroin Dependent: A Resting-state FMRI Study

With the development of medical equipment and modern techniques inimage processing technologies, there have been a lot of scientific findings aboutunderlying mechanisms of drug addiction. Like other drug-related research,heroin addiction is considered as a complex brain disorder involving theprocessing of cognition and affection. A large number of previous studies aboutheroin focused on structural damage in the brain under specific tasks, and thechanges of the brain among heroin addicts, compared to healthy subjects. Recentstudies have begun to investigate drug addiction from an overall perspective,and the assessment of resting state networks have been used for heroin addiction.The important features of heroin addiction is the impulsive behaviors to seekdrugs regardless of the consequences, however, people do not understand the relationship between these behaviors and the patterns of abnormal neuralnetwork. On the other hand, the study of addiction treatment is generallyperformed on the cellular and molecular level to assess the role of treatment ofdrugs and its efficacy, and further, the influence of drugs upon addiction-relatedneurotransmitters is also explored in animal models. However, these resultscannot make sure whether it is effective for functional connectivity neuralnetwork to induce addictive behaviors. To clarify these questions, thetechnology of resting-state magnetic resonance imaging was used in the presentstudy to detail the model characteristics of three subdivisions in the anteriorcingulate cortex (ACC) among the heroin addicts and healthy subjects. Inaddition, the relationship between the intensity of function connectivity in ACCfunctional connectivity neural networks and the total scores of BarrattImpulsiveness Scale was also analyzed by linear regression analysis andcorrelation analysis. What’more, heroin addicts were randomly divided into twotreatment groups: l-tetrahydropalmatine (l-THP) and the placebo treatment.After three months of treatment, the protracted withdrawal symptoms in heroinaddicts and the intervention in functional link of the ACC neural networks werealso observed.In this study, the functional links among the three ACC functional partitionswere detailedly mapped. The findings showed the significant difference in thethree neural networks between heroin addicts and healthy individuals. Thedifferences concerned reward, motivation, control inhibition, memory, learning,and so on, and they were changed in very complex ways. It was found that thebrain regions negatively correlated with the impulsive behaviors was the criticalareas to inhibit impulsive behaviors.In the dorsal anterior cingulate cortex impulsive networks, compared to healthy adults, brain regions of heroin addicts negatively correlated with theimpulsive behaviors were transferred from medial frontal and inferior parietallobule to the inferior temporal gyrus. In the rostral anterior cingulate corteximpulsive networks, the negative-related brain regions of heroin addicts weretransferred from the lateral prefrontal and inferior parietal lobule to the inferiortemporal gyrus and dorsal medial prefrontal cortex. The orbital frontal cortexwas the main negative-related brain regions in subcallosal anterior cingulatecortex network in the healthy control group, while the same regions were morenegatively related to the limbic system in the heroin group, which demonstratedthat the critical functions of the brain areas related to the inhibition of impulsivebehavior in healthy adults were diminished or reversed in the impulsive networkof heroin addicts, and they were replaced by areas of the brain related toemotion and reward systems. And further, both of the two groups’ impulsivenetworks were overlaid to get the common brain regions related to ACCimpulsive network, suggesting that location of these specific brain regions wereclosely related to impulsive behaviors.In the present study, symptom self-rating scale, Pittsburgh Sleep QualityIndex and the Hamilton Depression Rating Scale were used to monitor theinvention effct of l-THP on protracted withdrawal symptoms among the heroinaddicts, and the changes of the networks of the three ACC regions betweenbefore and after treatment were compared by the resting-state magneticresonance imaging.The results showed that after12weeks of continuous treatment, theprotracted withdrawal symptoms in l-THP and placebo groups were bothimproved, but there were no significant differences between them, suggestingthat these symptoms could be naturally self-improved. The main features of protracted withdrawal symptoms included physical discomfort, sleepdisturbance, and anxiety. We found that l-THP to improve the physicaldiscomfort and sleep disturbance. It was also found that l-THP played a greatrole in improving physical discomfort and sleep disturbance, especially in themedium-term treatment. However, such positive effect was reduced, as thetreatment went on, which indicated that there was certain resistance to l-THP,and its effect upon anxiety still needed discussing.Magnetic resonance imaging study results showed that the l-THP couldrelieve the heroin addicts’ protracted withdrawal symptoms significantly;however, such improvement was not synchronized with functional recovery inneural network. In the dorsal anterior cingulate networks, l-THP exerts effectmainly upon the dorsal medial prefrontal cortex, ventral Posterior cingulatedcortex, parahippocampal gyrus and lingual gyrus. In the rostral anteriorcingulate networks, the effects of l-THP were put on lingual gyrus, the ventralmedial frontal and rostral lateral prefrontal gyrus. In the subcallosal anteriorcingulated cortex network, onlyRetrosplenial cortex and thalamus wereinfluenced by l-THP. In addition, the effects of l-THP upon the left and rightanterior cingulate networks were asymmetric. Specifically, it was also found thatl-THP put side effects on striaturn, which would impede the natural recovery ofneurological function, and even worse, the function would be furtherdeteriorated. Different from the prominent effect of l-THP in the animal model,the present study suggested that the possible adverse factors should beconsidered when l-THP was used to treat drug addiction.To sum up, the functional neural network models in ACC among heroinaddicts were significantly different from those among healthy adults, and theanterior cingulate functional connectivity neural networks related to impulsive behaviors were reconstructed. The treatment of l-THP could effectively promotethe improvement of protracted withdrawal symptoms, but only induce limitedrecovery of functions in the brain regions in the neural network level. It isnoticeable that much more attention also should be focused upon the adverseeffect of the medicine on the recovery of brain functions.