Cohen Michael S, Rissman Jesse, Suthana Nanthia A, Castel Alan D, Knowlton Barbara J
Department of Psychology, University of California, Los Angeles, CA, 90095, USA,
Cogn Affect Behav Neurosci. 2014 Jun;14(2):578-92. doi: 10.3758/s13415-014-0275-x.
A number of prior fMRI studies have focused on the ways in which the midbrain dopaminergic reward system coactivates with hippocampus to potentiate memory for valuable items. However, another means by which people could selectively remember more valuable to-be-remembered items is to be selective in their use of effective but effortful encoding strategies. To broadly examine the neural mechanisms of value on subsequent memory, we used fMRI to assess how differences in brain activity at encoding as a function of value relate to subsequent free recall for words. Each word was preceded by an arbitrarily assigned point value, and participants went through multiple study-test cycles with feedback on their point total at the end of each list, allowing for sculpting of cognitive strategies. We examined the correlation between value-related modulation of brain activity and participants' selectivity index, which measures how close participants were to their optimal point total, given the number of items recalled. Greater selectivity scores were associated with greater differences in the activation of semantic processing regions, including left inferior frontal gyrus and left posterior lateral temporal cortex, during the encoding of high-value words relative to low-value words. Although we also observed value-related modulation within midbrain and ventral striatal reward regions, our fronto-temporal findings suggest that strategic engagement of deep semantic processing may be an important mechanism for selectively encoding valuable items.
此前的一些功能磁共振成像（fMRI）研究聚焦于中脑多巴胺能奖赏系统与海马体共同激活以增强对有价值物品记忆的方式。然而，人们能够选择性地记住更有价值的待记忆物品的另一种方式是在使用有效但费力的编码策略时保持选择性。为了广泛研究价值对后续记忆的神经机制，我们使用功能磁共振成像来评估编码时大脑活动随价值的差异如何与单词的后续自由回忆相关。每个单词之前都有一个随机分配的分值，参与者经历多个学习 - 测试循环，并在每个列表结束时得到关于他们总分的反馈，这有助于塑造认知策略。我们研究了大脑活动的价值相关调制与参与者的选择性指数之间的相关性，该指数衡量在给定回忆项目数量的情况下，参与者与他们的最佳总分有多接近。更高的选择性分数与高价值单词相对于低价值单词编码期间语义处理区域（包括左下额叶回和左后外侧颞叶皮质）激活的更大差异相关。虽然我们也在中脑和腹侧纹状体奖赏区域观察到了价值相关调制，但我们的额颞叶研究结果表明，深度语义处理的策略性参与可能是选择性编码有价值物品的重要机制。
