Study On Decision-making Alternation After Bilateral Nucleus Accumbens Ablation In Drug Addicts.

BackgroundDecision making is one of the most important parts of the human cognition function.IGT is a empirical method that simulates human's decision-making process in daily life.This test was first invented by Bechara in 1994.At first,it was used in the research on the decision-making deficit of the patients who had suffered VentralMedial Prefrontal Cortex(VMPC) injury[97].Later ,it was utilized to study the decision-making deficit in other disease such as Pathological Gambling, Obsessive Compulsive Disorder, etc.It has been proved to be a sensitive and stable tool.[101]。IGT result of drug addictsCompulsive drug-seeking behavior is a key character of drug addiction and a main reason leading to relapse.Now the relapse rate reach to 90% after ordinary therapy. When faced with the temptation of drug,even at the risk of incurring future negative outcomes,including loss of reputation,job,and family,they always can't stop themselves from choicing drug.This phenomenon indicate the dicision-making deficit of drug addicts.[101]。 During Iowa gambling test,63% of addicts prefomed abnormally and 27% performed normally[101].This result was proved by other independent experiments.[98].Antoni'review showed that decision-making deficit caused by opiate is a long-lasting deficit[137].So this deficit may play a important role in the relaps.Based on addicts'performance on IGT,Bechara raise a new theory:drug addicts can not make right choice according to the future outcomes.they prefer immediate reward and appear oblivious to the consequences of their actions.This deficit is hard to be erased[101].While during IGT,27% of normal control perform abnormally.Bechara proposed that this result was caused by personal behavior mode and this part of people are thought to be more easily affected by drug[101].Whiside and Lynam divide the impulsive character into four parts,they are Urgency,Lack of premediatation,Lack of perseverance,and Sensation seeking[104]. Ariane Z'research revealed that Lack Of Premeditation affected IGT result more obviously[102]. Althouth IGT has been proved to be a sensitive and stable tool[101] .while how to explain it's result is still in controversy.Barnaby's review pro-posed that Besides Bechara's decision-making deficit theory, other factors, such as education,age,working memory,risk taking,reversal learning/behavior inhibition ,can also affect people's IGT result[98].Our department started to cure opiate dependence by ablating the nucleus accumbens bilaterally by stereostatic sugery from 2000.A follow-up more than one years showed that this surgery can lower the relaps rate to 33.3% with no obvious complication[125]. Ablating the nucleus accumbens bilaterally has been proves to be a effective therapy for drug addiction.But what happened to decision-making after sugery has not been reported.This rearch intend to explore decision-making alternation after bilateral Nucleus Accumbens ablation in drug addicts and analyse the reason.ObjectiveTo explore decision-making alternation after bilateral Nucleus Accumbens ablation in drug addicts and analyse the reason.MethodWe tested 15 opiate-dependent individuals by using Iowa gambling task, Cambridge gambling task,Go/no-go task and Digit span task before and 14 days after bilateral Nucleus Accumbens ablation and campared their performances with those of 14 normal controls. Levene test of homogeneity of varianc and LSD-t test was used in Statistics analysis.ResultIt was shown that the opiate-dependent subjects'IGT performances became better after surgery (a = 0.05,p < 0.01)and had no significant difference compared with the controls (a = 0.05,p < 0.01) .While difference of their performances in other three tasks had no statistical sense(a=0.1,p >0.1).ConclusionsNucleus Accumbens ablation can improve opiate-dependent subjects'performances in IGT and has no effect on such neuropsychological functions as working memory,risk-taking and behavior inhibition.