Department of Psychology, University of Pennsylvania, Philadelphia, PA, 19104, USA.
Penn Memory Center, University of Pennsylvania, Philadelphia, PA, 19104, USA; Department of Neurology, University of Pennsylvania, Philadelphia, PA, 19104, USA.
Neuropsychologia. 2020 Sep;146:107549. doi: 10.1016/j.neuropsychologia.2020.107549. Epub 2020 Jul 2.
When facing decisions involving trade-offs between smaller, sooner and larger, delayed rewards, people tend to discount the value of future rewards. There are substantial individual differences in this tendency toward temporal discounting, however. One neurocognitive system that may underlie these individual differences is episodic memory, given the overlap in the neural circuitry involved in imagining the future and remembering the past. Here we tested this hypothesis in older adults, including both those that were cognitively normal and those with amnestic mild cognitive impairment (MCI). We found that performance on neuropsychological measures of episodic memory retrieval was associated with temporal discounting, such that people with better memory discounted delayed rewards less. This relationship was specific to episodic memory and temporal discounting, since executive function (another cognitive ability) was unrelated to temporal discounting, and episodic memory was unrelated to risk tolerance (another decision-making preference). We also examined cortical thickness and volume in medial temporal lobe regions critical for episodic memory. Entorhinal cortical thickness was associated with reduced temporal discounting, with episodic memory performance partially mediating this association. The inclusion of MCI participants was critical to revealing these associations between episodic memory and entorhinal cortical thickness and temporal discounting. These effects were larger in the MCI group, reduced after controlling for MCI status, and statistically significant only when including MCI participants in analyses. Overall, these findings suggest that individual differences in temporal discounting are driven by episodic memory function, and that a decline in medial temporal lobe structural integrity may impact temporal discounting.
当面临在较小、较早和较大、延迟奖励之间进行权衡的决策时，人们往往会低估未来奖励的价值。然而，在这种时间折扣的倾向方面，个体之间存在很大的差异。一种可能是基于情景记忆的神经认知系统，因为涉及想象未来和回忆过去的神经回路存在重叠。在这里，我们在老年人中测试了这一假设，包括认知正常和遗忘型轻度认知障碍（MCI）患者。我们发现，情景记忆的神经心理学测量表现与时间折扣有关，即记忆较好的人对延迟奖励的折扣程度较低。这种关系是情景记忆和时间折扣特有的，因为执行功能（另一种认知能力）与时间折扣无关，情景记忆与风险容忍度（另一种决策偏好）无关。我们还检查了内侧颞叶区域的皮质厚度和体积，这些区域对情景记忆至关重要。内嗅皮质厚度与时间折扣减少有关，情景记忆表现部分介导了这种关联。纳入 MCI 参与者对于揭示情景记忆和内嗅皮质厚度与时间折扣之间的这些关联至关重要。这些效应在 MCI 组中更大，在控制 MCI 状态后减少，并且仅在包括 MCI 参与者进行分析时才具有统计学意义。总体而言，这些发现表明，时间折扣的个体差异是由情景记忆功能驱动的，内侧颞叶结构完整性的下降可能会影响时间折扣。
