Department of Pharmacology and Physiology, and Institute for Neuroscience, George Washington University, 2300 Eye Street NW, Washington, DC 20037, USA.
Brain Res. 2019 Mar 1;1706:13-23. doi: 10.1016/j.brainres.2018.10.024. Epub 2018 Oct 23.
Inhibitory circuits in thalamus and cortex shape the major activity patterns observed by electroencephalogram (EEG) in the adult brain. Their delayed maturation and circuit integration, relative to excitatory neurons, suggest inhibitory neuronal development could be responsible for the onset of mature thalamocortical activity. Indeed, the immature brain lacks many inhibition-dependent activity patterns, such as slow-waves, delta oscillations and sleep-spindles, and instead expresses other unique oscillatory activities in multiple species including humans. Thalamus contributes significantly to the generation of these early oscillations. Compared to the abundance of studies on the development of inhibition in cortex, however, the maturation of thalamic inhibition is poorly understood. Here we review developmental changes in the neuronal and circuit properties of the thalamic relay and its interconnected inhibitory thalamic reticular nucleus (TRN) both in vitro and in vivo, and discuss their potential contribution to early network activity and its maturation. While much is unknown, we argue that weak inhibitory function in the developing thalamus allows for amplification of thalamocortical activity that supports the generation of early oscillations. The available evidence suggests that the developmental acquisition of critical thalamic oscillations such as slow-waves and sleep-spindles is driven by maturation of the TRN. Further studies to elucidate thalamic GABAergic circuit formation in relation to thalamocortical network function would help us better understand normal as well as pathological brain development.
丘脑和皮层中的抑制性回路塑造了成年人大脑脑电图（EEG）中观察到的主要活动模式。与兴奋性神经元相比，它们的成熟和回路整合延迟，表明抑制性神经元发育可能是成熟的丘脑皮层活动开始的原因。事实上，不成熟的大脑缺乏许多依赖抑制的活动模式，例如慢波、德尔塔振荡和睡眠纺锤波，而是在包括人类在内的多种物种中表达其他独特的振荡活动。丘脑对这些早期振荡的产生有重要贡献。然而，与皮层抑制发育的大量研究相比，丘脑抑制的成熟尚不清楚。在这里，我们回顾了体外和体内丘脑中继及其相互连接的抑制性丘脑网状核（TRN）的神经元和回路特性的发育变化，并讨论了它们对早期网络活动及其成熟的潜在贡献。虽然还有很多未知，但我们认为，发育中的丘脑抑制功能较弱，允许放大丘脑皮层活动，从而支持早期振荡的产生。现有证据表明，慢波和睡眠纺锤波等关键丘脑振荡的发育获得是由 TRN 的成熟驱动的。进一步研究阐明与丘脑皮层网络功能相关的丘脑 GABA 能回路形成，将有助于我们更好地理解正常和病理性脑发育。
