Relationship Between Impulsivity And Craving In Abstinent Drug-Dependent Individuals:Research On Behavior And The Brain Mechanism

Drug dependence is a very important health problem and represents the largest risk factor for family harmony and social stability. But when addicts want to abandon drug habits, they will face one hardest issue-high rate of relapse. Drug craving may represent a very important risk factor for high rate of relapse. Craving is proposed to be defined as "strong desire or mandatory urge to use a specific substance".Impulsivity is defined as a predisposition toward rapid, unplanned reactions to internal or external stimuli without regarding the negative consequences of these reactions to oneself or others.Evidence suggests that the concept of impulsivity is firmly interconnected with craving and substance abuse. Impulsivity is often described also as the main behavioral characteristic of drug abusers, and the multidimensional nature of impulsivity construct can be discriminating between ’trait impulsivity’(stable personality characteristic) and’state impulsivity’ which is temporarily determined by environmental variables, which the environmental variables can be split into normal situation and ego depletion situation.The relationship between the multidimensional nature of impulsivity construct and craving, however, has not been studied, especially the relationship between state impulsivity and craving in different situations. And the neural mechanism of the effect of impulsivity on craving is not yet fully understood.In order to study the relationship between impulsivity construct and craving in its entirety, we intends to research on behavior and the brain mechanism. The use of both questionnaires and multiple laboratory tasks of impulsive behavior may help us to discriminating between ’trait impulsivity’ and’state impulsivity’. And how is the relationship between the impulse and desire in the condition of lack of self-control. We also use fMRI to explore the neural mechanism of the relationship between impulsivity construct and craving, recording the brain activity when the drugs addicts viewing drug pictures.In Experiment1, we want to probe into the relationship between trait impulsivity and craving. To this end,49abstinent drug-dependent individuals were screened using Barratt Impulsiveness Scale (BIS-11) and Behavioral Inhibition/Activation System Scale (BIS/BAS).We use Cue-Viewing Task presented with six blocks to measure cue-elicited craving. The results showed that trait impulsivity is not linked to more intense cue-elicited craving for drug in all abstinent drug-dependent patients. But this relationship is significant in heavy dependence severity, not in low. There is much reliance to be researched trait impulsivity using BIS-11, compared with BIS/BAS.In Experiment2, we want to explore the relationship between state impulsivity and craving in abstinent drug-dependent patients. Experiment2is divided into two experiments: we explore the relationship in normal situation in Experiment2A; and study the relationship in ego depletion position in Experiment2B.In Experiment2A, state impulsivity is measured by classical Stroop task and Go/No-go task.25detoxified heroin-dependent patients and11methamphetamine-dependent subjects were enrolled. We find a similar conclusion. Such as state impulsivity is not linked to more cue-elicited craving for drug in all patients; the relationship is significant in heavy dependence severity, not in low. There is also much reliance to be researched state impulsivity using Stroop task, compared with Go/No-go task.In Experiment2B, we want to explore the relationship between impulsivity and craving in the depletion situation, using the dual task paradigm to control32patients’impulsivity. We firstly test all subjects’impulsivity using pre-Stroop test, and then engaging in self-control at time1sets in motion a pair of interdependent and iterative processes that culminate in poorer self-control at time2. We find that patients experience more intense craving for alcohol when exposed to drug rather than to neutral cues. There is no significant relationship between pre-Stroop test, but the relationship between post-Stroop test’ accuracy is significant positive correlation, suggesting that impulsivity predict craving easily in ego depletion position.In Experiment3, we want to explore the neural mechanism of the relationship between impulsivity and craving. We use fMRI to recording the brain activity when the drugs addicts viewing drug or similar pictures. We find that heroin-addicts show more activation to drug than to similar images in many areas, such as Anterior Cingulate, Inferior Frontal Gyrus, Amygdala, Parahippocampa Gyrus, and Middle Temporal Gyrus. During the scan negative correlations between BOLD activity and SDS scores were observed in areas of Caudate Nucleus; we also find positive correlations between the Caudate Nucleus’ activation and trait impulsivity, and negative correlations between the Orbitofrontal Cortex and state impulsivity. It’s suggested that rait impulsivity is associated with reward system, while the state impulse is closely related to the executive control system of drug addicts.In conclusion, we can draw the following conclusion.1) The addiction severity influences the relationship between impulsivity and craving, which we can find the significantly positive correlation in high addicts, not in low addicts.2) It’s suggesting that state impulsivity predicts craving easily in ego depletion position. 3) In point of neural mechanism, trait impulsivity is associated with reward system, while the state impulse is closely related to the executive control system of drug addicts.