Mohns Ethan J, Blumberg Mark S
Program in Behavioral and Cognitive Neuroscience, Department of Psychology, University of Iowa, Iowa City, Iowa 52242, USA.
J Neurosci. 2008 Oct 1;28(40):10134-44. doi: 10.1523/JNEUROSCI.1967-08.2008.
The neonatal hippocampus exhibits regularly recurring waves of synchronized neuronal activity in vitro. Because active sleep (AS), characterized by bursts of phasic motor activity in the form of myoclonic twitching, may provide conditions that are conducive to activity-dependent development of hippocampal circuits, we hypothesized that the waves of synchronous neuronal activity that have been observed in vitro would be associated with AS-related twitching. Using unanesthetized 1- to 12-d-old rats, we report here that the majority of neurons in CA1 and the dentate gyrus (DG) are significantly more active during AS than during either quiet sleep or wakefulness. Neuronal activity typically occurs in phasic bursts, during which most neurons are significantly cross-correlated both within and across the CA1 and DG fields. All AS-active neurons increase their firing rates during periods of myoclonic twitching of the limbs, and a subset of these neurons exhibit a burst of activity immediately after limb twitches, suggesting that the twitches themselves provide sensory feedback to the infant hippocampus, as occurs in the infant spinal cord and neocortex. Finally, the synchronous bursts of neuronal activity are coupled to the emergence of the AS-related hippocampal gamma rhythm during the first postnatal week, as well as the emergence of the AS-related theta rhythm during the second postnatal week. We hypothesize that the phasic motor events of active sleep provide the developing hippocampus with discrete sensory stimulation that contributes to the development and refinement of hippocampal circuits as well as the development of synchronized interactions between hippocampus and neocortex.
新生海马体在体外表现出有规律的同步神经元活动波。由于以肌阵挛性抽搐形式出现的阶段性运动活动爆发为特征的主动睡眠（AS）可能提供有利于海马体回路依赖活动发育的条件，我们推测在体外观察到的同步神经元活动波将与AS相关的抽搐有关。使用未麻醉的1至12日龄大鼠，我们在此报告，CA1和齿状回（DG）中的大多数神经元在AS期间比在安静睡眠或清醒期间明显更活跃。神经元活动通常以阶段性爆发的形式出现，在此期间，大多数神经元在CA1和DG区域内以及跨区域之间都存在显著的交叉相关性。所有在AS期间活跃的神经元在四肢肌阵挛性抽搐期间都会提高其放电率，并且这些神经元中的一部分在肢体抽搐后立即表现出一阵活动，这表明抽搐本身会向婴儿海马体提供感觉反馈，就像在婴儿脊髓和新皮层中发生的那样。最后，神经元活动的同步爆发与出生后第一周AS相关的海马体γ节律的出现以及出生后第二周AS相关的θ节律的出现相关联。我们推测，主动睡眠的阶段性运动事件为发育中的海马体提供离散的感觉刺激，这有助于海马体回路的发育和完善以及海马体与新皮层之间同步相互作用的发展。
