Modulators of 8 Hz theta rhythm recorded in the human hippocampus

Theta节律是脑电图（EEG）信号中的8Hz神经振荡模式，其与海马体的功能相关，海马体是对情景记忆和空间记忆至关重要的脑区域。θ节律的一个据称功能是使海马体中的神经元的活动同步，作为编码新记忆的机制。Theta节律与空间记忆、运动行为、行走速度和觉醒有关。在啮齿类动物中消除θ波段的低频振荡（LFO）会导致空间学习和记忆受损。2017年，我们在Nature Group期刊Nature Communications上发表了第一个明确的证据，即人类海马内深度电极的8 Hz theta节律。 目的：我的研究计划的总体目标是评估调节θ节律的因素，以进一步表征与人类学习和记忆相关的这种振荡模式。具体来说，我们将评估步行速度、导航策略、认知训练和睡眠对人类θ节律的影响。 假设：1、行走速度：啮齿类动物的文献表明，行走速度是海马体θ节律的重要调节因子，因为行走速度会影响在太空中行驶的距离。我们假设步行速度将对人类的θ节律产生重大影响。 2)导航策略：文献表明，不同的导航策略依赖于不同的记忆系统，即海马和尾状核。我们假设，主要使用依赖于校园的导航策略导航的个人将显示出显着更强的θ节律。 3)空间记忆训练：对人类和啮齿动物的研究表明，空间记忆训练可以增加海马体中的灰质。因此，我们假设空间记忆训练将在两周内增加θ节律。 4)睡眠：对啮齿动物的研究表明，睡眠在神经元放电的重演中起着重要作用。我们假设，与使用尾状核依赖策略的人相比，使用海马依赖导航策略的人在睡眠期间会观察到明显更强的θ波。我们还假设，在两周的空间记忆训练后，睡眠相关的θ节律会更大。 这项研究将有助于弥合啮齿动物和人类关于θ节律在学习和记忆中的作用的文献。此外，我们还有一个独特的机会来进一步探索人类θ活动以及调节它的因素，以便更好地了解促进人类导航技能和寻路能力的因素。

Theta rhythm is an 8 Hz neural oscillatory pattern in electroencephalography (EEG) signals that is associated with function of the hippocampus, a brain region that is crucial for episodic memory and spatial memory. One purported function of theta rhythm is to synchronize activity of neurons in the hippocampus as a mechanism for coding novel memories. Theta rhythm has been associated with spatial memory, motor behaviour, speed of walking, and arousal. Removing low-frequency oscillations (LFO) in the theta band in rodents resulted in impaired spatial learning and memory. In 2017, we published in a Nature Group Journal, Nature Communications, the first clear evidence of 8 Hz theta rhythm from intra-hippocampal depth electrodes in humans. Objectives: The overarching goal of my research program is to assess factors that modulate theta rhythm in order to further characterize this oscillatory pattern associated with learning and memory in humans. Specifically, we will assess the impact of speed of walking, navigation strategies, cognitive training, and sleep on human theta rhythm. Hypotheses: 1) Speed of walking: The rodent literature shows that speed of walking is an important modulator of hippocampus theta rhythm because walking speed will have an impact on the distance travelled in space. We hypothesize that speed of walking will have a significant impact on theta rhythm in humans. 2) Navigation strategies: The literature shows that different navigation strategies rely on separate memory systems, namely the hippocampus and the caudate nucleus. We hypothesize that individuals who navigate primarily using hippocampus-dependent navigation strategies will show significantly stronger theta rhythm. 3) Spatial memory training: Research in both humans and rodents shows that spatial memory training can increase grey matter in the hippocampus. As such, we hypothesize that spatial memory training will increase theta rhythm over a period of two weeks. 4) Sleep: Research in rodents has shown an important role for sleep in the replay of ensembles of neuronal firing. We hypothesize that significantly stronger theta will be observed during sleep for individuals who use hippocampus-dependent navigation strategies compared to those who use caudate nucleus-dependent strategies. We also hypothesize that sleep-related theta rhythm will be greater following the two weeks of spatial memory training. The studies proposed in this grant will be fundamental to help bridge the rodent and human literatures on the role of theta rhythm in learning and memory. In addition, we have a unique opportunity to further explore human theta activity and the factors that modulate it in order to gain a better understand on factors that promote navigation skills and wayfinding abilities in humans.