Theta Dynamics in Rat: Speed and Acceleration across the Septotemporal Axis

Theta (6–12 Hz) rhythmicity in the local field potential (LFP) reflects a clocking mechanism that brings physically isolated neurons together in time, allowing for the integration and segregation of distributed cell assemblies. Variation in the theta signal has been linked to locomotor speed, sensorimotor integration as well as cognitive processing. Previously, we have characterized the relationship between locomotor speed and theta power and how that relationship varies across the septotemporal (long) axis of the hippocampus (HPC). The current study investigated the relationship between whole body acceleration, deceleration and theta indices at CA1 and dentate gyrus (DG) sites along the septotemporal axis of the HPC in rats. Results indicate that whole body acceleration and deceleration predicts a significant amount of variability in the theta signal beyond variation in locomotor speed. Furthermore, deceleration was more predictive of variation in theta amplitude as compared to acceleration as rats traversed a linear track. Such findings highlight key variables that systematically predict the variability in the theta signal across the long axis of the HPC. A better understanding of the relative contribution of these quantifiable variables and their variation as a function of experience and environmental conditions should facilitate our understanding of the relationship between theta and sensorimotor/cognitive functions.

大脑局部场电位（local field potential, LFP）中6–12 Hz的θ节律，反映了一种将物理上分离的神经元在时间维度上同步整合的计时机制，可实现分布式细胞集群的信息整合与功能分离。θ信号的变异与运动速度、感觉运动整合以及认知加工过程密切相关。此前本团队已明确了运动速度与θ功率之间的关联，以及该关联沿海马体（hippocampus, HPC）隔颞长轴的变化规律。本研究以大鼠为实验对象，探究了其全身加速、减速行为与海马体隔颞轴上CA1区及齿状回（dentate gyrus, DG）位点的θ指标之间的关联。研究结果显示，相较于仅由运动速度带来的变异，全身加速与减速行为可显著解释θ信号的更多变异性。此外，当大鼠在直线轨道上运动时，减速行为对θ振幅变异的预测能力要强于加速行为。上述发现明确了可系统性预测海马体长轴θ信号变异性的关键变量。深入理解这些可量化变量的相对贡献，及其随实验经验与环境条件变化的规律，将有助于进一步阐明θ节律与感觉运动、认知功能之间的关联机制。