Urbano Francisco J, Kezunovic Nebojsa, Hyde James, Simon Christen, Beck Paige, Garcia-Rill Edgar
Instituto de Fisiología, Biología Molecular y Neurociencias, Consejo Nacional de Investigaciones Científicas y Técnicas, University of Buenos Aires Buenos Aires, Argentina.
Front Neurol. 2012 Jan 31;3:6. doi: 10.3389/fneur.2012.00006. eCollection 2012.
This review considers recent evidence showing that cells in three regions of the reticular activating system (RAS) exhibit gamma band activity, and describes the mechanisms behind such manifestation. Specifically, we discuss how cells in the mesopontine pedunculopontine nucleus (PPN), intralaminar parafascicular nucleus (Pf), and pontine subcoeruleus nucleus dorsalis (SubCD) all fire in the beta/gamma band range when maximally activated, but no higher. The mechanisms behind this ceiling effect have been recently elucidated. We describe recent findings showing that every cell in the PPN have high-threshold, voltage-dependent P/Q-type calcium channels that are essential, while N-type calcium channels are permissive, to gamma band activity. Every cell in the Pf also showed that P/Q-type and N-type calcium channels are responsible for this activity. On the other hand, every SubCD cell exhibited sodium-dependent subthreshold oscillations. A novel mechanism for sleep-wake control based on well-known transmitter interactions, electrical coupling, and gamma band activity is described. The data presented here on inherent gamma band activity demonstrates the global nature of sleep-wake oscillation that is orchestrated by brainstem-thalamic mechanism, and questions the undue importance given to the hypothalamus for regulation of sleep-wakefulness. The discovery of gamma band activity in the RAS follows recent reports of such activity in other subcortical regions like the hippocampus and cerebellum. We hypothesize that, rather than participating in the temporal binding of sensory events as seen in the cortex, gamma band activity manifested in the RAS may help stabilize coherence related to arousal, providing a stable activation state during waking and paradoxical sleep. Most of our thoughts and actions are driven by pre-conscious processes. We speculate that continuous sensory input will induce gamma band activity in the RAS that could participate in the processes of pre-conscious awareness, and provide the essential stream of information for the formulation of many of our actions.
本综述探讨了近期证据，这些证据表明网状激活系统（RAS）三个区域的细胞呈现γ波段活动，并描述了这种表现背后的机制。具体而言，我们讨论了中脑桥脑脚桥核（PPN）、板内核束旁核（Pf）和脑桥背侧蓝斑下核（SubCD）的细胞在最大激活时如何都在β/γ波段范围内放电，但不会更高。这种上限效应背后的机制最近已得到阐明。我们描述了近期的研究发现，即PPN中的每个细胞都有高阈值、电压依赖性的P/Q型钙通道，这些通道对γ波段活动至关重要，而N型钙通道则是允许性的。Pf中的每个细胞也表明P/Q型和N型钙通道负责这种活动。另一方面，每个SubCD细胞都表现出钠依赖性阈下振荡。描述了一种基于众所周知的递质相互作用、电耦合和γ波段活动的睡眠-觉醒控制新机制。这里呈现的关于固有γ波段活动的数据证明了由脑干-丘脑机制精心安排的睡眠-觉醒振荡的全局性，并质疑了下丘脑在调节睡眠-觉醒方面被赋予的过度重要性。RAS中γ波段活动的发现紧随近期在海马体和小脑等其他皮层下区域出现这种活动的报道之后。我们假设，RAS中表现出的γ波段活动可能不像在皮层中那样参与感觉事件的时间绑定，而是有助于稳定与觉醒相关的连贯性，在清醒和异相睡眠期间提供稳定的激活状态。我们的大多数思想和行动是由前意识过程驱动的。我们推测，持续的感觉输入将在RAS中诱导γ波段活动，这可能参与前意识觉知过程，并为我们许多行动的形成提供基本的信息流。
