Motivation deficits, such as apathy, are pervasive in both neurological and psychiatric diseases. Even when they are not the core symptom, they reduce quality of life, compromise functional outcome and increase the burden for caregivers. They are currently assessed with clinical scales that do not give any mechanistic insight susceptible to guide therapeutic intervention. Here, we present another approach that consists of phenotyping the behaviour of patients in motivation tests, using computational models. These formal models impose a precise and operational definition of motivation that is embedded in decision theory. Motivation can be defined as the function that orients and activates the behaviour according to two attributes: a content (the goal) and a quantity (the goal value). Decision theory offers a way to quantify motivation, as the cost that patients would accept to endure in order to get the benefit of achieving their goal. We then review basic and clinical studies that have investigated the trade-off between the expected cost entailed by potential actions and the expected benefit associated with potential rewards. These studies have shown that the trade-off between effort and reward involves specific cortical, subcortical and neuromodulatory systems, such that it may be shifted in particular clinical conditions, and reinstated by appropriate treatments. Finally, we emphasize the promises of computational phenotyping for clinical purposes. Ideally, there would be a one-to-one mapping between specific neural components and distinct computational variables and processes of the decision model. Thus, fitting computational models to patients’ behaviour would allow inferring of the dysfunctional mechanism in both cognitive terms (e.g. hyposensitivity to reward) and neural terms (e.g. lack of dopamine). This computational approach may therefore not only give insight into the motivation deficit but also help personalize treatment.

中文翻译：

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为什么不更努力呢？神经精神疾病中动机缺陷的计算方法

神经系统疾病和精神疾病都普遍存在动机缺乏症，例如冷漠。即使不是核心症状，它们也会降低生活质量，损害功能结局并增加护理人员的负担。目前，他们使用的临床量表进行了评估，这些量表并未提供任何易于指导治疗干预的机制性见解。在这里，我们提出了另一种方法，该方法包括使用计算模型在动机测试中对患者的行为进行表型化。这些形式化模型强加了对动机的精确和可操作的定义，该定义嵌入了决策理论。动机可以定义为根据两个属性来定向和激活行为的功能：内容（目标）和数量（目标值）。决策理论提供了一种量化动机的方法，病人为了获得实现其目标的利益而承受的承受的成本。然后，我们回顾了基础和临床研究，这些研究调查了潜在行动带来的预期成本和与潜在回报相关的预期收益之间的折衷。这些研究表明，努力与报酬之间的权衡涉及特定的皮层，皮层下和神经调节系统，因此在特定的临床条件下可能会发生改变，并通过适当的治疗方法将其恢复。最后，我们强调了用于临床目的的计算机表型的前景。理想情况下，特定神经组件与决策模型的不同计算变量和过程之间将存在一对一的映射。因此，将计算模型拟合到患者的行为将可以推断认知功能障碍（例如对奖励的超敏性）和神经功能障碍（例如缺乏多巴胺）的功能障碍机制。因此，这种计算方法不仅可以洞察动力不足，还可以帮助个性化治疗。