Department of Psychology and Delta Center, University of Iowa, Iowa City, Iowa 52242, USA.
J Neurosci. 2010 Mar 3;30(9):3438-49. doi: 10.1523/JNEUROSCI.4832-09.2010.
We recently reported that the majority of hippocampal neurons in newborn rats increase their activity in association with myoclonic twitches, which are indicative of active sleep. Because spindle bursts in the developing somatosensory neocortex occur in response to sensory feedback from myoclonic twitching, we hypothesized that the state-dependent activity of the newborn hippocampus arises from sensory feedback that sequentially activates the neocortex and then hippocampus, constituting an early form of neocortical-hippocampal communication. Here, in unanesthetized 5- to 6-d-old rats, we test this hypothesis by recording simultaneously from forelimb and barrel regions of somatosensory neocortex and dorsal hippocampus during periods of spontaneous sleep and wakefulness and in response to peripheral stimulation. Myoclonic twitches were consistently followed by neocortical spindle bursts, which were in turn consistently followed by bursts of hippocampal unit activity; moreover, spindle burst power was positively correlated with hippocampal unit activity. In addition, exogenous stimulation consistently evoked this neocortical-to-hippocampal sequence of activation. Finally, parahippocampal lesions that disrupted functional connections between the neocortex and hippocampus effectively disrupted the transmission of both spontaneous and evoked neocortical activity to the hippocampus. These findings suggest that sleep-related motor activity contributes to the development of neocortical and hippocampal circuits and provides a foundation on which coordinated activity between these two forebrain structures develops.
我们最近报道称，新生大鼠的大多数海马神经元会随着肌阵挛抽搐而增加活动，这表明它们处于活跃睡眠状态。由于发育中的体感新皮层中的纺锤波爆发是对肌阵挛抽搐的感觉反馈的反应，我们假设新生海马体的状态依赖活动源于感觉反馈，该反馈依次激活新皮层和海马体，构成了新皮层-海马体通讯的早期形式。在这里，我们在未麻醉的 5 至 6 日龄大鼠中通过在自发睡眠和觉醒期间以及响应外周刺激时同时从体感新皮层的前肢和桶状皮层区域以及背侧海马体进行记录来检验这一假说。肌阵挛抽搐始终伴随着新皮层纺锤波爆发，而纺锤波爆发又始终伴随着海马体单位活动的爆发；此外，纺锤波爆发的功率与海马体单位活动呈正相关。此外，外源性刺激始终能诱发这种新皮层到海马体的激活序列。最后，破坏新皮层和海马体之间功能连接的旁海马体损伤有效地破坏了自发和诱发的新皮层活动向海马体的传递。这些发现表明，与睡眠相关的运动活动有助于新皮层和海马体回路的发育，并为这两个前脑结构之间的协调活动发展提供了基础。
