Data from: Synchronized excitability in a network enables generation of internal neuronal sequences

Hippocampal place field sequences are supported by sensory cues and network internal mechanisms. In contrast, sharp-wave (SPW) sequences, theta sequences, and episode field sequences are internally generated. The relationship of these sequences to memory is unclear. SPW sequences have been shown to support learning and have been assumed to also support episodic memory. Conversely, we demonstrate these SPW sequences were present in trained rats even after episodic memory was impaired and after other internal sequences – episode field and theta sequences – were eliminated. SPW sequences did not support memory despite continuing to ‘replay’ all task-related sequences – place- field and episode field sequences. Sequence replay occurred selectively during synchronous increases of population excitability -- SPWs. Similarly, theta sequences depended on the presence of repeated synchronized waves of excitability – theta oscillations. Thus, we suggest that either intermittent or rhythmic synchronized changes of excitability trigger sequential firing of neurons, which in turn supports learning and/or memory.

海马位置场序列（Hippocampal place field sequences）的维持依赖于感觉线索与神经网络内部机制。与之相对，锐波（sharp-wave, SPW）序列、θ节律序列（theta sequences）与事件场序列（episode field sequences）均为内部生成的神经活动模式。目前此类序列与记忆的关联机制尚不明确。已有研究证实锐波序列可支持学习过程，且学界此前普遍认为其同样参与情景记忆（episodic memory）的编码与提取。与之相反，本研究结果显示：即便在训练大鼠的情景记忆受损、其余内部序列（事件场序列与θ节律序列）完全消失后，锐波序列仍可被稳定检测到。尽管锐波序列仍持续“重放”所有任务相关序列——包括位置场序列与事件场序列，但其并未参与记忆支持过程。序列重放仅选择性地发生于群体兴奋性（population excitability）同步增强的时段，即锐波事件期间。同理，θ节律序列的产生依赖于重复性同步兴奋性波动，即θ振荡（theta oscillations）的存在。据此，我们提出假说：间歇性或节律性的同步兴奋性变化可触发神经元的顺序放电活动，进而支撑学习与/或记忆过程。