SIMULATION OF SPATIAL-LEARNING IN THE MORRIS WATER MAZE BY A NEURAL-NETWORK MODEL OF THE HIPPOCAMPAL-FORMATION AND NUCLEUS-ACCUMBENS
SIMULATION OF SPATIAL-LEARNING IN THE MORRIS WATER MAZE BY A NEURAL-NETWORK MODEL OF THE HIPPOCAMPAL-FORMATION AND NUCLEUS-ACCUMBENS
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DOI：
10.1002/hipo.450050304
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发表时间：
1995-01-01
期刊：
影响因子：
3.5
通讯作者：
SHARP, PE
中科院分区：
文献类型：
--
作者：
BROWN, MA;SHARP, PE
海马结构中的细胞显示出空间放电相关性，这被认为对该结构在空间学习中所发挥的作用至关重要。海马体中的位置细胞表现出特定位置的活动，而枕后细胞则显示出瞬时方向性的函数。一个很少受到关注的问题是运动结构如何使用这些空间信号来实际指导空间行为。在这里，我们提出了一个模型，说明一种空间行为，即莫里斯水迷宫中的工具学习，如何由海马结构中的空间信息来指导。为此，我们专注于海马向伏隔核的投射，这与工具学习密切相关。在模型中，位置细胞和头部方向细胞的模拟放电模式激活“伏隔核”中的“运动”细胞。每个运动细胞在模拟大鼠中引起特定的运动。通过这种方式，“老鼠”可以在模拟环境中移动。每一步都会将动物置于稍微不同的位置和方向，这反过来又激活一组不同的位置和头部方向细胞，从而引起下一个运动反应，依此类推。小区之间的连接强度最初是随机设置的。然而，当动物遇到奖励位置时，连接就会改变，因此最近活跃的突触会得到加强。因此，在特定位置和方向环境中的成功移动被“标记”。模拟老鼠表现出快速的学习能力，在很多方面与真实老鼠相似。特别是，它们在最少的经验后生成到达目标的有效路线，并且可以从有些新颖的起始位置做到这一点。对模型架构的考虑表明，1）方向和位置信息的组合使用是线性不可分问题的一个例子，2）某些类型的新颖路线生成（通常被认为需要“认知映射”策略）可以从此处使用的 S-R 类型模型生成。 (C) 1995 Wiley-Liss, Inc.
Cells in the hippocampal formation show spatial firing correlates thought to be critical to the role played by this structure in spatial learning. Place cells in the hippocampus proper show location-specific activity, whereas cells in the postsubiculum fire as a function of momentary directional heading.One question which has received little attention is how these spatial signals are used by motor structures to actually guide spatial behavior.Here we present a model of how one kind of spatial behavior, instrumental learning in the Morris water maze, could be guided by the spatial information in the hippocampal formation. For this, we concentrate on the hippocampal projection to the nucleus accumbens, which is strongly implicated in instrumental learning.In the model, simulated firing patterns of place cells and head direction cells activate ''motor'' cells in the ''accumbens.'' Each motor cell causes a particular locomotor movement in a simulated rat. In this way, the ''rat'' locomotes through the simulated environment. Each step places the animal in a slightly different location and directional orientation, which, in turn, activates a different set of place and head direction cells, thus causing the next locomotor response, and so on. Connection strengths between cells are initially set randomly. When the animal encounters the reward location, however, connections are altered, so that recently active synapses are strengthened. Thus, successful moves in a particular locational and directional context are ''stamped in.''Simulated rats show rapid learning, similar in many ways to that of actual rats. in particular, they generate efficient routes to the goal after minimal experience, and can do so from somewhat novel starting positions.Consideration of the model architecture shows that 1) combined use of directional and place information is an example of a linearly inseparable problem and that 2) some types of novel route generation, often thought to require a ''cognitive mapping'' strategy, can be generated from the S-R type model used here. (C) 1995 Wiley-Liss, Inc.