Turner Institute for Brain and Mental Health, School of Psychological Sciences, Monash University, Melbourne, Australia.
Addict Biol. 2024 Jan;29(1):e13356. doi: 10.1111/adb.13356.
People with methamphetamine use disorder (MUD) struggle to shift their behaviour from methamphetamine-orientated habits to goal-oriented choices. The model-based/model-free framework is well suited to understand this difficulty by unpacking the computational mechanisms that support experienced-based (model-free) and goal-directed (model-based) choices. We aimed to examine whether 1) participants with MUD differed from controls on behavioural proxies and/or computational mechanisms of model-based/model-free choices; 2) model-based/model-free decision-making correlated with MUD symptoms; and 3) model-based/model-free deficits improved over six weeks in the group with MUD. Participants with MUD and controls with similar age, IQ and socioeconomic status completed the Two-Step Task at treatment commencement (MUD n = 30, Controls n = 31) and six weeks later (MUD n = 23, Controls n = 26). We examined behavioural proxies of model-based/model-free decisions using mixed logistic regression, and their underlying mechanisms using computational modelling. At a behavioural level, participants with MUD were more likely to switch their choices following rewarded actions, although this pattern improved at follow up. At a computational level, groups were similar in their use of model-based mechanisms, but participants with MUD were less likely to apply model-free mechanisms and less likely to repeat rewarded actions. We did not find evidence that individual differences in model-based or model-free parameters were associated with greater severity of methamphetamine dependence, nor did we find that group differences in computational parameters changed between baseline and follow-up assessment. Decision-making challenges in people with MUD are likely related to difficulties in pursuing choices previously associated with positive outcomes.
患有甲基苯丙胺使用障碍（MUD）的人难以将他们的行为从以甲基苯丙胺为导向的习惯转变为以目标为导向的选择。基于模型/无模型框架非常适合通过分解支持基于经验（无模型）和目标导向（基于模型）选择的计算机制来理解这种困难。我们旨在研究以下几点：1）与对照组相比，患有 MUD 的参与者在基于模型/无模型选择的行为替代物和/或计算机制上是否存在差异；2）基于模型/无模型决策是否与 MUD 症状相关；3）患有 MUD 的参与者在六周内基于模型/无模型的缺陷是否得到改善。患有 MUD 的参与者和具有相似年龄、智商和社会经济地位的对照组在治疗开始时（MUD n=30，对照组 n=31）和六周后（MUD n=23，对照组 n=26）完成了两步任务。我们使用混合逻辑回归检查了基于模型/无模型决策的行为替代物，并用计算模型检查了其潜在机制。在行为层面上，患有 MUD 的参与者在受到奖励后更有可能改变他们的选择，尽管这种模式在随访时有所改善。在计算层面上，两组在使用基于模型的机制方面相似，但患有 MUD 的参与者不太可能使用无模型机制，也不太可能重复受到奖励的行为。我们没有发现基于模型或无模型参数的个体差异与甲基苯丙胺依赖的严重程度相关的证据，也没有发现组间计算参数在基线和随访评估之间发生变化的证据。患有 MUD 的人的决策挑战可能与难以追求以前与积极结果相关的选择有关。
