Long-term Potentiation and Neural Coding of Learning, Memory in Rat Hippocampus

(1)本文研究了低频（1Hz）或高频（100 Hz）电刺激大鼠海马CA 1区位置细胞活动与支架侧支的相互作用。高频stimelation损害随机游走和空间导航任务，颅内自我刺激作为奖励的动机。然而，低频刺激并不损害其行为。高频刺激抑制了位置细胞的活动，结果，位置场在刺激后立即消失。1小时内，神经活动和任务完成均恢复到对照组水平。然而，恢复的位置场与对照不同。在同一电极上进行低频刺激也能改变位置场。这表明，在CA 1神经元的位置依赖可能是通过CA 3的Schaffer侧支实现的，并且与LTP或LTD相关的高频信息可能与位置加工相关。(2)通过对两种神经元活动的相关性分析，验证了海马神经元的板层假说。在清醒和麻醉状态下同时记录大鼠海马CA 1区两种神经元活动。清醒状态下的归一化互相关值小于麻醉状态。CA 1锥体层复合峰电位在间隔1.1mm以上的隔颞轴上呈沿着相关，在清醒和麻醉状态下呈几乎一致的互相关值0.02-0.1。提示海马CA 1区神经元之间可能存在着弱的分布联系。

(1) Interaction between place cell activity in rat hippocampal CA1 and low (1Hz) or high (100Hz) frequency electrical stimulation of the Scaffer collaterals was studied. High frequency stimelation impaired both random wandering and spatial navigation tasks, motivated by intracranial self-stimulation as a reward. However, low frequency stimulation did not impair its behaviors. The place cell activity was suppressed by high frequency stimulation and, as a result, the place field disappeared just after the stimulation. Within an hour, the nueronal activity and performance of task were recovered to the control level. However, the place fields recovered were different from the control. Low frequency stimulation on the same electrode also modified place field. These suggest that the place dependency in the CA1 neuron may be implemented through the Schaffer collateral of CA3, and that high or frequency information related to the LTP or LTD might be correlated to the place processing.(2) Lamella hypothesis in rat hippocampus was tested by correlation analysis of two neuronal activities. The two neuronal activities of rat hippocampal CA1 area were simultaneously recorded in an awake and anesthezed state. The normalized cross-correlation values in awake state were smaller than ones of anesthesia state. The complex-spike activity of CA1 pyramidal layr was correlated along septo-temporal axis over 1.1mm apart and showed almost uniform cross-correlation values of 0.02-0.1 in both awake and anesthesia state. These suggest that the neuron in hippocampal CA1 area may connect each other with weak distributed manners.