3D spatial coding in the monkey hippocampus

自O’keefe发现海马位置细胞以来，人们对啮齿动物海马空间认知的神经基础进行了大量研究，但对灵长类动物海马位置细胞的认识有限。本研究的目的是记录猴子在三维环境中运动时海马的神经元活动，并阐明动物的运动方向（水平和垂直）与位置反应之间的关系。传统的通过信号传输电缆记录神经元活动是有问题的，因为它会干扰猴子在具有复杂结构的3D环境中的运动。之前我们在一个由水平和垂直运动空间以l形相连组成的3D环境中训练猴子，发现猴子的运动在l形末端受到限制，这可能会给分析神经元活动带来困难。因此，本财年我们完成了一个方形甜甜圈形状的3D环境。在这个财政年度，我们首先训练了一只恒河猴在这个3D环境中顺时针和逆时针方向移动。我们还开发了一个基于人工智能的猴子行为监测系统，能够识别猴子的位置和姿势。然后，通过手术给猴子头上戴上一顶颅骨整形帽；目前正在进行诱发电位映射，以准确估计记录神经元活动的最佳位置。

Since the discovery of hippocampal place cells by O'Keefe, there have been many studies on the neural basis of spatial cognition in the rodent hippocampus, but knowledge on primate hippocampal place cells is limited. The purpose of this study was to record neuronal activity from the hippocampus of monkeys moving in a 3D environment, and to clarify the relationship between the animal's direction of movement (horizontal and vertical) and place responsiveness. Conventional recording of neuronal activity via signal transmission cables is problematic because it interferes with the movement of monkeys in a 3D environment with complex structures. Previously we trained the monkeys in a 3D environment consisting of horizontal and vertical moving spaces connected in an L-shape, and found the movement of the monkey was restricted at the L-shaped ends, which could make it difficult to analyze neuronal activity. Therefore, this fiscal year we completed a square doughnut-shaped 3D environment. In this fiscal year, we first and trained a rhesus monkey to move in clockwise and counter-clockwise directions in this 3D environment. We also developed an AI-based monkey behavior monitoring system capable of identifying the monkey's position and pose. Then, a cranioplastic head cap was surgically attached to the head of the monkey; evoked potential mapping is currently being conducted to accurately estimate the optimal location for recording neuronal activity.