慢性海洛因成瘾者的冲动性和行为抑制缺陷脑机制

In recent years, the deficit of inhibition has become an important reason for explaining addiction. Response inhibition resembles the compulsive drug seeking behavior and it is the basement of addiction inhibition deficits. However, there were no enough evidence for the relationship between addiction and response inhibition deficits and the results of the neuro mechanisms studies remains unclear. Few studies has focused on the exploring the heroin users. Among those paradigms for study response inhibition deficits, stop signal is a very suitable model for the representation of compulsive drug seeking, but only a few researches has worked on this paradigm. In this study, we selected about 100 heroin abusers and had behaviour and neuro imaging scannings for investigating the response inhibition deficits. The behaviour researches found: first, the chronic heroin users had longer reaction time than control group and this reaction time were not affected by stop signals in heroin users. Second, heroin users had less waiting time than control group and they were more impulsive but less flexibility. Their erro monitoring and flexibale adjustment ability decreased. Third, the SSRT of heroin users was significantly longer than control group. These results suggested that the inhibition of heroin users were impaired. Further investigation showed that the SSRT of heroin users had positive correlation of four factor scores of ASI and the macro correlation coefficient was factor three of drug use. This correlation suggested that drug use was the main reason of inhibition deficits. fMRI results mainly focused on the ANOVA analysis for group difference. First, there was no intensity difference in M1 and SMA brain areas between the two groups. Second, heroin users had less activation in right dorsalateral prefrontal cortex, right inferior prefrontal cortex and anterior cingulated cortex, while in bilateral striatum and amygdala, heroin users had more activation than control group. The right prefrontal cortex was indentified as the main inhibition brain area. The anterior cingulated cortex has relationship with erro monitoring and amygdale was an important brain area for impulsivity and emotion control. The network of these brain areas was envovled in impulsivity and inhibition and it was suggested the mainly damaged network for heroin users’ disinhibition. We also investigated the gray matter changes of heroin users and found that chonic heroin use made their gray matter density decreased in prefrontal cortex (including bilateral dorsalateral prefrontal cortex, obital frontal cortex, inferior prefrontal cortex) and anterior cingulated cortex. The gray matter density in these brain regions had negative correlation with drug use duration. In conclusion, we indentified the disinhibition of heroin users and its neuro mechanism. Their compulsivity brain areas had more activation than control group and their inhibition brain areas had less activation than normal control. On the other side, the biological mechanism of this activation changes was the gray matter density decrease in these brain areas.

海洛因成瘾者决策障碍及其行为机制的研究----短视行为及冲动、强迫和药物在决策中的作用

Addiction can be investigated from the perspective of decision making. Addicts usually make incorrect decisions when facing drug-related cues or they are driven to drugs, resulting in repeated drug seeking and taking. The present study adopted temporal discounting as behavioral task and on the basis of the fact that heroin addicts discounted more steeply than health participants (addicts preferred to choose immediate but smaller reward, regarded as myopia) which was consistent with previous research, three questions was raised and being concentrated on in this study. The first question was whether the character of myopia would be revealed in a somewhat complicated task? We designed a card game in which the participants were tested whether they would play the trump card in order to win a trick but not the whole game. Addicts played the trump card significantly earlier than controls did, indicating they focused on immediate single trick but not the game. Moreover, the performance in the card game and temporal discounting correlated significantly, suggesting addicts would display myopic decision not only in simply task like temporal discounting but also in task more complicated and similar to daily-life decision. Secondly, the present study adopted various kinds of temporal discounting tasks. In previous research, temporal discounting gain task was usually adopted. In the present study, we also adopted temporal discounting loss task. In either gain or loss task, there are two delayed amounts. Results showed in each decision condition addicts made poorer performance compared with control but in larger amount condition, addicts actually improved their decision performance. Meanwhile, addicts did not show loss aversion due to their close discount rates in gain and loss task while for controls, the discount rates were much lower in loss task than those in gain task. Thus we demonstrated that addicts were insensitive to negative outcomes by the method of temporal discounting. Finally, we investigated three mechanisms which exerted impacts on decision making. We adopted Go/NoGo task to test impulsivity and found addicts commits more errors (higher impulsivity) than controls did. We also designed a behavioral task which could be used to test drug-related compulsive behavior on human participants. Results showed addicts produced stereotyped key-pressing behavior when presented with drug-related cues. Furthermore, it was found participants with higher impulsivity displayed poorer performance in decision making but addicts with higher compulsivity only made poorer performance in smaller amount decision and the correlation between compulsivity and decision making was relative weak. In order to investigate the role of susceptibility and effect of drugs, we adopted years of abusing heroin as the indictor and discovered addicts with longer history of heroin abusing made poorer performance in smaller amount condition than addicts with shorter history. Also, the earlier the addicts began to use drug, the worse they would do in the smaller amount decision. The results here indicated drug itself could exert impact on decision making in certain condition. The present study revealed three characters of heroin addicts from the aspect of decision making: (1) focusing upon current benefit due to they preferred to choose immediate gain and delayed loss; (2) showed no loss aversion compared with healthy participants (3) inability to inhibit inappropriate response particularly when facing drug-related cue. These characters contribute to the facts that addicts seek and take drugs repeatedly while ignoring the negative consequences caused by abusing drugs.

比较型算术应用题一致性效应的实验研究

As former research shown, the error rate of consistent compare word problem (such as: Mary has 5 apples, Tom has 2 apples more than Mary, how many apples does Tom has?) is much lower than the rate of inconsistent compare word problem (such as: Mary has 5 apples, she has 2 apples more than Tom, how many apples does Tom has?). This difference of error rate is named as Consistency Effect. There are different explanations about why consistency effect happens, one of them is R.E.Mayer's opinion about two kinds of problem solving strategies. As Mayer's opinion, unsuccessful problem solvers make mistakes on inconsistent problem because they use Direct Translation Strategy, problem solvers who use Problem Model Strategy will not make such kind of mistakes. In this study, three experiments with 3~(rd) graders investigate reasons for the consistency effect. The results of experiment 1 do not support the explanation of Mayer's theory of two kinds of strategy. Experiment 2 shows that there is no relation between inconsistent problem error and Impulsivity cognitive style. Experiment 3 reveals that the working memory capacity of successful inconsistent problem solvers is significant larger than the capacity of unsuccessful solvers. It is supposed that working memory could be an important factor contributing for the consistency effect.