美国哈佛医学院Rachel I. Wilson团队发现，多巴胺促进定向运动中头部方向的可塑性。相关论文于2022年11月30日在线发表于国际学术期刊《自然》。

研究人员表示，在将信息储存在其连接权重中的神经网络中，在敏感性和稳定性之间存在着一种权衡。连接必须是可塑的，以纳入新的信息，但如果它们的可塑性太强，存储的信息就会被破坏。一个潜在的解决方案是在“何时学习”信号的基础上，只允许在特定任务信息丰富的时段进行可塑性训练。

研究人员推断，多巴胺提供了一个“何时学习”的信号，使大脑的空间地图在新的空间信息可用时（即动物在移动时）得以更新。研究人员表明支配果蝇头部方向网络的多巴胺神经元在果蝇转身改变其头部方向时特别活跃。此外，它们的活动与旋转速度的瞬间波动成比例。将多巴胺释放与视觉线索配对，可以持续加强线索对头部方向细胞的影响。相反，抑制这些多巴胺神经元会减少线索的影响。这种机制应该在定向运动提供丰富的头部方向信息流的时候加速学习，使学习率在其他时候较低以保护储存的信息。

这些研究结果表明，大脑中的空间学习可以被压缩成不连续的时间段，其中高学习率与高信息摄入率相匹配。

附：英文原文

Title: Dopamine promotes head direction plasticity during orienting movements

Author: Fisher, Yvette E., Marquis, Michael, DAlessandro, Isabel, Wilson, Rachel I.

Issue&Volume: 2022-11-30

Abstract: In neural networks that store information in their connection weights, there is a tradeoff between sensitivity and stability1,2. Connections must be plastic to incorporate new information, but if they are too plastic, stored information can be corrupted. A potential solution is to allow plasticity only during epochs when task-specific information is rich, on the basis of a ‘when-to-learn’ signal3. We reasoned that dopamine provides a when-to-learn signal that allows the brain’s spatial maps to update when new spatial information is available—that is, when an animal is moving. Here we show that the dopamine neurons innervating the Drosophila head direction network are specifically active when the fly turns to change its head direction. Moreover, their activity scales with moment-to-moment fluctuations in rotational speed. Pairing dopamine release with a visual cue persistently strengthens the cue’s influence on head direction cells. Conversely, inhibiting these dopamine neurons decreases the influence of the cue. This mechanism should accelerate learning during moments when orienting movements are providing a rich stream of head direction information, allowing learning rates to be low at other times to protect stored information. Our results show how spatial learning in the brain can be compressed into discrete epochs in which high learning rates are matched to high rates of information intake.

DOI: 10.1038/s41586-022-05485-4

Source: https://www.nature.com/articles/s41586-022-05485-4