Fuhs Mark C, Touretzky David S
Computer Science Department, Center for the Neural Basis of Cognition, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
J Neurosci. 2006 Apr 19;26(16):4266-76. doi: 10.1523/JNEUROSCI.4353-05.2006.
Electrophysiological recording studies in the dorsocaudal region of medial entorhinal cortex (dMEC) of the rat reveal cells whose spatial firing fields show a remarkably regular hexagonal grid pattern (Fyhn et al., 2004; Hafting et al., 2005). We describe a symmetric, locally connected neural network, or spin glass model, that spontaneously produces a hexagonal grid of activity bumps on a two-dimensional sheet of units. The spatial firing fields of the simulated cells closely resemble those of dMEC cells. A collection of grids with different scales and/or orientations forms a basis set for encoding position. Simulations show that the animal's location can easily be determined from the population activity pattern. Introducing an asymmetry in the model allows the activity bumps to be shifted in any direction, at a rate proportional to velocity, to achieve path integration. Furthermore, information about the structure of the environment can be superimposed on the spatial position signal by modulation of the bump activity levels without significantly interfering with the hexagonal periodicity of firing fields. Our results support the conjecture of Hafting et al. (2005) that an attractor network in dMEC may be the source of path integration information afferent to hippocampus.
对大鼠内嗅皮质内侧背尾区域（dMEC）进行的电生理记录研究表明，该区域的细胞其空间放电场呈现出非常规则的六边形网格模式（Fyhn等人，2004年；Hafting等人，2005年）。我们描述了一种对称的、局部连接的神经网络，即自旋玻璃模型，它能在二维单元片上自发产生六边形的活动峰网格。模拟细胞的空间放电场与dMEC细胞的放电场非常相似。一组具有不同尺度和/或方向的网格构成了编码位置的基集。模拟表明，从群体活动模式中可以很容易地确定动物的位置。在模型中引入不对称性，可使活动峰以与速度成正比的速率在任何方向上移动，以实现路径积分。此外，通过调制峰活动水平，可将有关环境结构的信息叠加在空间位置信号上，而不会显著干扰放电场的六边形周期性。我们的结果支持了Hafting等人（2005年）的推测，即dMEC中的吸引子网络可能是传入海马体的路径积分信息的来源。
