Department of Neurology, Geisel School of Medicine, Hanover, New Hampshire.
Hippocampus. 2013 Dec;23(12):1269-79. doi: 10.1002/hipo.22164. Epub 2013 Aug 5.
Hippocampal theta rhythm is believed to play a critical role in learning and memory. In animal models of temporal lobe epilepsy (TLE), there is evidence that alterations of hippocampal theta oscillations are involved in the cognitive impairments observed in this model. However, hippocampal theta frequency and amplitude at both the local field potential (LFP) and single unit level are strongly modulated by running speed, suggesting that the integration of locomotor information into memory processes may also be critical for hippocampal processing. Here, we investigate whether hippocampal speed-theta integration influences spatial memory and whether it could account for the memory deficits observed in TLE rats. LFPs were recorded in both Control (CTR) and TLE rats as they were trained in a spatial alternation task. TLE rats required more training sessions to perform the task at CTR levels. Both theta frequency and power were significantly lower in the TLE group. In addition, speed/theta frequency correlation coefficients and regression slopes varied from session to session and were worse in TLE. Importantly, there was a strong relationship between speed/theta frequency parameters and performance. Our analyses reveal that speed/theta frequency correlation with performance cannot merely be explained by the direct influence of speed on behavior. Therefore, variations in the coordination of theta frequency with speed may participate in learning and memory processes. Impairments of this function could explain at least partially memory deficits in epilepsy.
海马体θ节律被认为在学习和记忆中起着关键作用。在颞叶癫痫（TLE）的动物模型中，有证据表明海马体θ振荡的改变与该模型中观察到的认知障碍有关。然而，海马体在局部场电位（LFP）和单个单元水平上的θ频率和幅度都受到跑步速度的强烈调制，这表明将运动信息整合到记忆过程中对于海马体处理也可能是至关重要的。在这里，我们研究了海马体速度-θ整合是否会影响空间记忆，以及它是否可以解释 TLE 大鼠中观察到的记忆缺陷。当 CTR 和 TLE 大鼠在空间交替任务中接受训练时，我们记录了 LFPs。TLE 大鼠需要更多的训练课程才能达到 CTR 水平。TLE 组的θ频率和功率明显较低。此外，速度/θ频率相关系数和回归斜率随时间而变化，在 TLE 中更差。重要的是，速度/θ频率参数与性能之间存在很强的关系。我们的分析表明，速度/θ频率与性能的相关性不能仅仅用速度对行为的直接影响来解释。因此，θ频率与速度的协调变化可能参与学习和记忆过程。这种功能的障碍至少可以部分解释癫痫中的记忆缺陷。
