Adaptive coding of reward is the process by which neurons adapt their response to the context of available compensations. Higher rewards lead to a stronger brain response, but the increase of the response depends on the range of available rewards. A steeper increase is observed in a narrow range, and a more gradual slope in a wider range. In schizophrenia, adaptive coding appears affected in different domains, and in the reward domain in particular. Here we tested adaptive coding of reward in a large group of patients with schizophrenia (N = 86) and controls (N = 66). We assessed 1) the association between adaptive coding deficits and symptoms; 2) the longitudinal stability of deficits (the same task was performed three months apart); 3) the stability of results between two experimental sites. We used fMRI and the Monetary Incentive Delay task to assess participant’ adaptation to two different reward ranges: a narrow and a wide range. We used a region of interest analysis, evaluating adaptation within striatal and visual regions. Patients and controls underwent a full demographic and clinical assessment. We found reduced adaptive coding in patients, due to a decreased slope in the narrow reward range, with respect to that of control participants in striatal but not visual regions. This pattern was observed at both research sites. Upon re-test, patients increased their narrow range slopes, showing improved adaptive coding, whereas controls slightly reduced them. At re-test, patients with overly steep slopes in the narrow range also showed higher levels of negative symptoms. Our data confirm deficits in reward adaptation in schizophrenia and reveal a practice effect in patients, leading to improvement, with steeper slopes upon retest. However, in some patients, an overly steep slope may result in poor discriminability of larger rewards, due to early saturation of the brain response. Together, the loss of precision of reward representation in new (first exposure, underadaptation) and more familiar (re-test, overadaptation) situations may contribute to the multiple motivational symptoms in schizophrenia.

中文翻译：

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精神分裂症奖励的适应性编码、其随时间的变化以及与冷漠的关系

奖励的自适应编码是神经元根据可用补偿环境调整其反应的过程。更高的奖励会导致更强的大脑反应，但反应的增强取决于可用奖励的范围。在较窄的范围内观察到较陡的增加，在较宽的范围内观察到较平缓的斜率。在精神分裂症中，适应性编码似乎在不同领域受到影响，特别是在奖励领域。在这里，我们在一大群精神分裂症患者 (N = 86) 和对照组 (N = 66) 中测试了奖励的适应性编码。我们评估了 1）适应性编码缺陷与症状之间的关联； 2）赤字的纵向稳定性（相隔三个月执行相同的任务）； 3）两个实验点之间结果的稳定性。我们使用功能磁共振成像和货币激励延迟任务来评估参与者对两种不同奖励范围的适应：窄范围和宽范围。我们使用感兴趣区域分析来评估纹状体和视觉区域内的适应性。患者和对照接受了全面的人口统计和临床评估。我们发现，由于窄奖励范围的斜率降低，患者的适应性编码减少，相对于对照参与者，纹状体区域而非视觉区域的斜率降低。在两个研究地点都观察到了这种模式。重新测试后，患者增加了窄范围斜率，显示出自适应编码的改善，而对照组则略微降低了斜率。在重新测试时，在狭窄范围内坡度过陡的患者也表现出较高水平的阴性症状。我们的数据证实了精神分裂症患者奖励适应的缺陷，并揭示了患者的实践效果，导致改善，重新测试后斜率更陡。然而，在某些患者中，由于大脑反应过早饱和，过于陡峭的斜率可能会导致较大奖励的辨别能力较差。总之，在新的（首次接触、适应不足）和更熟悉的（重新测试、过度适应）情况下奖励表征的精确性丧失可能会导致精神分裂症的多种动机症状。