Schmitzer-Torbert Neil, Redish A David
Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota 55455, USA.
J Neurophysiol. 2004 May;91(5):2259-72. doi: 10.1152/jn.00687.2003. Epub 2004 Jan 21.
The striatum plays an important role in "habitual" learning and memory and has been hypothesized to implement a reinforcement-learning algorithm to select actions to perform given the current sensory input. Many experimental approaches to striatal activity have made use of temporally structured tasks, which imply that the striatal representation is temporal. To test this assumption, we recorded neurons in the dorsal striatum of rats running a sequential navigation task: the multiple T maze. Rats navigated a sequence of four T maze turns to receive food rewards delivered in two locations. The responses of neurons that fired phasically were examined. Task-responsive phasic neurons were active as rats ran on the maze (maze-responsive) or during reward receipt (reward-responsive). Neither maze- nor reward-responsive neurons encoded simple motor commands: maze-responses were not well correlated with the shape of the rat's path and most reward-responsive neurons did not fire at similar rates at both food-delivery sites. Maze-responsive neurons were active at one or more locations on the maze, but these responses did not cluster at spatial landmarks such as turns. Across sessions the activity of maze-responsive neurons was highly correlated when rats ran the same maze. Maze-responses encoded the location of the rat on the maze and imply a spatial representation in the striatum in a task with prominent spatial demands. Maze-responsive and reward-responsive neurons were two separate populations, suggesting a divergence in striatal information processing of navigation and reward.
纹状体在“习惯性”学习和记忆中发挥着重要作用，并且有人提出假设，认为纹状体通过执行强化学习算法，根据当前的感觉输入来选择要执行的动作。许多研究纹状体活动的实验方法都采用了具有时间结构的任务，这意味着纹状体的表征具有时间性。为了验证这一假设，我们记录了大鼠背侧纹状体中执行序列导航任务（多重T迷宫任务）的神经元活动。大鼠要依次完成四个T迷宫转弯，才能在两个位置获得食物奖励。我们检查了相位性放电神经元的反应。任务响应性相位神经元在大鼠在迷宫中奔跑时（迷宫响应）或在获得奖励时（奖励响应）处于活跃状态。迷宫响应神经元和奖励响应神经元均未编码简单的运动指令：迷宫响应与大鼠路径的形状相关性不佳，并且大多数奖励响应神经元在两个食物投放点的放电频率并不相似。迷宫响应神经元在迷宫的一个或多个位置处活跃，但这些反应并未聚集在诸如转弯处等空间地标处。当大鼠运行相同的迷宫时，不同实验时段内迷宫响应神经元的活动高度相关。迷宫响应编码了大鼠在迷宫中的位置，这意味着在具有突出空间需求的任务中，纹状体中存在空间表征。迷宫响应神经元和奖励响应神经元是两个不同的群体，这表明纹状体在导航和奖励信息处理方面存在差异。
