Department of Neurophysiology, University of Yamanashi, Chuo, Japan.
Front Neural Circuits. 2022 May 12;16:842748. doi: 10.3389/fncir.2022.842748. eCollection 2022.
Reaching, grasping, and retrieving movements are essential to our daily lives and are common in many mammalian species. To understand the mechanism for controlling this movement at the neural circuit level, it is necessary to observe the activity of individual neurons involved in the movement. For stable electrophysiological or optical recordings of neural activity in a behaving animal, head fixation effectively minimizes motion artifacts. Here, we developed a new device that allows mice to perform reaching, grasping, and retrieving movements during head fixation. In this method, agar cubes were presented as target objects in front of water-restricted mice, and the mice were able to reach, grasp, and retrieve them with their forelimb. The agar cubes were supplied by a custom-made automatic dispenser, which uses a microcontroller to control the two motors to push out the agar cubes. This agar presentation system supplied approximately 20 agar cubes in consecutive trials. We confirmed that each agar cube could be presented to the mouse with an average weight of 55 ± 3 mg and positional accuracy of less than 1 mm. Using this system, we showed that head-fixed mice could perform reaching, grasping, and retrieving tasks after 1 week of training. When the agar cube was placed near the mice, they could grasp it with a high success rate without extensive training. On the other hand, when the agar cube was presented far from the mice, the success rate was initially low and increased with subsequent test sessions. Furthermore, we showed that activity in the primary motor cortex is required for reaching movements in this task. Therefore, our system can be used to study neural circuit mechanisms for the control and learning of reaching, grasping, and retrieving movements under head-fixed conditions.
伸手、抓握和取回动作对于我们的日常生活至关重要，并且在许多哺乳动物物种中都很常见。为了在神经回路水平上理解控制这种运动的机制，有必要观察参与运动的单个神经元的活动。为了在行为动物中稳定地进行神经活动的电生理或光学记录，头部固定有效地最小化运动伪影。在这里，我们开发了一种新的设备，允许老鼠在头部固定的情况下进行伸手、抓握和取回动作。在这种方法中，琼脂块作为目标物体呈现在缺水的老鼠面前，老鼠可以用前肢伸手、抓握和取回它们。琼脂块由定制的自动分配器提供，该分配器使用微控制器控制两个电机将琼脂块推出。该琼脂提供系统在连续试验中提供了大约 20 个琼脂块。我们证实，每个琼脂块可以以平均 55±3mg 的重量和小于 1mm 的位置精度呈现给老鼠。使用该系统，我们表明经过 1 周的训练，头部固定的老鼠可以完成伸手、抓握和取回任务。当琼脂块放在老鼠附近时，它们可以以高成功率抓住它，而无需广泛的训练。另一方面，当琼脂块从老鼠身上取出时，成功率最初较低，并且随着后续测试会话的增加而增加。此外，我们表明，在这项任务中，初级运动皮层的活动对于伸手运动是必需的。因此，我们的系统可用于研究在头部固定条件下控制和学习伸手、抓握和取回运动的神经回路机制。
