Blair H T, Sharp P E
Department of Psychology, Yale University, New Haven, Connecticut 06520-8205, USA.
J Neurosci. 1995 Sep;15(9):6260-70. doi: 10.1523/JNEUROSCI.15-09-06260.1995.
Several regions in the rat brain contain neurons known as head-direction cells, which fire only when the rat's head is facing in a specific direction. Head-direction cells are influenced only by the direction of the head with respect to the static environmental surroundings, and not by the position of the head relative to the body. Each head-direction cell has its own preferred direction of firing, so that together, the population of cells provides a continuous signal of momentary directional heading. Here, head-direction cells were recorded from the post-subicular cortex (PSC) and anterodorsal nucleus (ADN) of the thalamus of freely moving rats. Cell activity was analyzed in relation to both momentary head direction, and the angular velocity of head turns. Head-direction cells in PSC maintained the same directional firing preference, regardless of the angular head velocity. By contrast, head-direction cells in ADN systematically shifted their directional firing preference, as a function of angular head velocity. The ADN cells always shifted their directional tuning peak to the left during clockwise head turns, and to the right during counterclockwise head turns. These results suggest that ADN neurons anticipate the future direction of the head, whereas PSC neurons encode the present direction of the head. Based on these findings, we hypothesize that neurons in PSC and ADN are reciprocally connected to form a thalamocortical circuit, which computes the directional position of the rat's head by integrating the angular motion of the head over time.
大鼠大脑中的几个区域含有被称为头部方向细胞的神经元，这些神经元仅在大鼠头部朝向特定方向时才会放电。头部方向细胞仅受头部相对于静态环境的方向影响，而不受头部相对于身体位置的影响。每个头部方向细胞都有自己偏好的放电方向，因此，这些细胞群体共同提供了一个关于瞬间方向朝向的连续信号。在这里，我们从自由活动大鼠丘脑的后下托皮质（PSC）和前背核（ADN）记录了头部方向细胞。分析了细胞活动与瞬间头部方向以及头部转动角速度的关系。PSC中的头部方向细胞保持相同的方向放电偏好，而与头部角速度无关。相比之下，ADN中的头部方向细胞会根据头部角速度系统地改变其方向放电偏好。ADN细胞在顺时针头部转动时总是将其方向调谐峰值向左移动，在逆时针头部转动时向右移动。这些结果表明，ADN神经元预测头部的未来方向，而PSC神经元编码头部的当前方向。基于这些发现，我们假设PSC和ADN中的神经元相互连接形成一个丘脑皮质回路，该回路通过整合头部随时间的角运动来计算大鼠头部的方向位置。
