en Cellular and molecular Neuroscience Cellular and molecular Neuroscience Original Original <p align="justify"><strong>A B S T R A C T</strong></p><p align="justify"><strong>Introduction:</strong> Although decision-making processes have become a principal target of study among addiction researchers, few researches are published according to effects of different treatment methods on the cognitive processes underlying decision making up to now. Utilizing cognitive modeling method, in this paper we examine the effects of Methadone maintenance treatment (MMT) on cognitive processes underlying decision-making disorders in heroin-abusers.</p><p style="DIRECTION: ltr" align="justify"> <strong>Methods:</strong> For this purpose, for the first time, we use the balloon analog risk task (BART) to assess the decision-making ability of heroin-abusers before and after treatment and compare it to the non heroin-dependent subjects.</p><p style="DIRECTION: ltr" align="justify"> <strong>Results:</strong> Results demonstrate that heroin-abusers show more risky behavior than other groups. But, there is no difference between the performance of heroin-abusers after 6 months of MMT and control group. Modeling subjects’ behavior in BART reveals that poor performance in heroin-abusers is due to reward-dependency and insensitivity to evaluation.</p><p align="justify"> <strong>Discussion:</strong> Results show that 6 months of MMT decreases reward-dependency and increases sensitivity to evaluation. </p> Cognitive modeling,Methadone maintenance,Balloon analogue risk task,Decision-making 44 49 http://bcn.iums.ac.ir/browse.php?a_code=A-10-1-32&slc_lang=en&sid=1 Arash Khodadadi 137003194753284600414 137003194753284600414 Yes School of Electrical Engineering, Iran University of Science & Technology, Neuro Cognitive Laboratory, Iranian National Center for Addiction Studies, Amir Dezfouli 137003194753284600415 137003194753284600415 No Center of Excellence for Control & Intelligent Processing Department of Electrical & Computer Engineering, Neuro Cognitive Laboratory, Iranian National Center for Addiction Studies, Pegah Fakhari 137003194753284600416 137003194753284600416 No Center of Excellence for Control & Intelligent Processing Department of Electrical & Computer Engineering, Hamed Ekhtiari 137003194753284600417 137003194753284600417 No Neuro Cognitive Laboratory, Iranian National Center for Addiction Studies,