小柯机器人

加拿大麦吉尔大学Mark P. Brandon等研究人员合作揭示漂移和重新定向时头部方向神经元的群体动态。该项研究成果于2023年3月22日在线发表在《自然》杂志上。

在视觉地标的受控旋转过程中，研究人员使用钙成像技术对丘脑高清细胞进行了群体记录。在整个实验中，群体活动沿着第二个维度变化，被称为网络增益，特别是在线索冲突和含糊不清的情况下。沿着这个维度的活动预测了重新排列和漂移的动态，包括网络重新排列的速度。在黑暗中，网络增益保持了对先前显示的地标的“记忆痕迹”。进一步的实验表明，在短暂的而非更长时间的接触到旋转的线索后，头部方向（HD）网络会回到其基线方向。这种经验依赖性表明，HD神经元和分配中心线索之间先前的关联记忆得到了保持，并影响了HD的内部表征。

在这些结果的基础上，研究人员表明，一个视觉地标的连续旋转诱发了在黑暗中持续存在的HD表征的旋转，这证明了HD系统的经验依赖性的重新校准。最后，研究人员提出了一个计算模型，用于正式说明神经罗盘如何灵活地适应不断变化的环境线索，从而维持一个可靠的HD表示。这些结果挑战了对HD系统的经典一维解释，并提供了对该系统与它所锚定的线索之间相互作用的洞察力。

据悉，HD系统作为大脑的内部指南针发挥作用，经典的形式化为一个一维环形吸引器网络。与全球一致的磁罗盘不同的是，HD系统没有一个普遍的参考框架。相反，它锚定在局部线索上，在线索旋转时保持稳定的偏移，并在没有参照物的情况下漂移。然而，关于锚定和漂移的机制问题仍未解决，最好在群体层面上解决。例如，在重新定向和漂移的条件下，群体活动的一维描述在多大程度上成立还不清楚。

附：英文原文

Title: Population dynamics of head-direction neurons during drift and reorientation

Author: Ajabi, Zaki, Keinath, Alexandra T., Wei, Xue-Xin, Brandon, Mark P.

Issue&Volume: 2023-03-22

Abstract: The head direction (HD) system functions as the brain’s internal compass1,2, classically formalized as a one-dimensional ring attractor network3,4. In contrast to a globally consistent magnetic compass, the HD system does not have a universal reference frame. Instead, it anchors to local cues, maintaining a stable offset when cues rotate5,6,7,8 and drifting in the absence of referents5,8,9,10. However, questions about the mechanisms that underlie anchoring and drift remain unresolved and are best addressed at the population level. For example, the extent to which the one-dimensional description of population activity holds under conditions of reorientation and drift is unclear. Here we performed population recordings of thalamic HD cells using calcium imaging during controlled rotations of a visual landmark. Across experiments, population activity varied along a second dimension, which we refer to as network gain, especially under circumstances of cue conflict and ambiguity. Activity along this dimension predicted realignment and drift dynamics, including the speed of network realignment. In the dark, network gain maintained a ‘memory trace’ of the previously displayed landmark. Further experiments demonstrated that the HD network returned to its baseline orientation after brief, but not longer, exposures to a rotated cue. This experience dependence suggests that memory of previous associations between HD neurons and allocentric cues is maintained and influences the internal HD representation. Building on these results, we show that continuous rotation of a visual landmark induced rotation of the HD representation that persisted in darkness, demonstrating experience-dependent recalibration of the HD system. Finally, we propose a computational model to formalize how the neural compass flexibly adapts to changing environmental cues to maintain a reliable representation of HD. These results challenge classical one-dimensional interpretations of the HD system and provide insights into the interactions between this system and the cues to which it anchors.

DOI: 10.1038/s41586-023-05813-2

Source: https://www.nature.com/articles/s41586-023-05813-2

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