Welle Cristin G, Contreras Diego
Division of Biomedical Physics, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, Maryland; and Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania.
Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
J Neurophysiol. 2016 Apr;115(4):1821-35. doi: 10.1152/jn.00137.2015. Epub 2015 Dec 30.
Gamma oscillations are a robust component of sensory responses but are also part of the background spontaneous activity of the brain. To determine whether the properties of gamma oscillations in cortex are specific to their mechanism of generation, we compared in mouse visual cortex in vivo the laminar geometry and single-neuron rhythmicity of oscillations produced during sensory representation with those occurring spontaneously in the absence of stimulation. In mouse visual cortex under anesthesia (isoflurane and xylazine), visual stimulation triggered oscillations mainly between 20 and 50 Hz, which, because of their similar functional significance to gamma oscillations in higher mammals, we define here as gamma range. Sensory representation in visual cortex specifically increased gamma oscillation amplitude in the supragranular (L2/3) and granular (L4) layers and strongly entrained putative excitatory and inhibitory neurons in infragranular layers, while spontaneous gamma oscillations were distributed evenly through the cortical depth and primarily entrained putative inhibitory neurons in the infragranular (L5/6) cortical layers. The difference in laminar distribution of gamma oscillations during the two different conditions may result from differences in the source of excitatory input to the cortex. In addition, modulation of superficial gamma oscillation amplitude did not result in a corresponding change in deep-layer oscillations, suggesting that superficial and deep layers of cortex may utilize independent but related networks for gamma generation. These results demonstrate that stimulus-driven gamma oscillations engage cortical circuitry in a manner distinct from spontaneous oscillations and suggest multiple networks for the generation of gamma oscillations in cortex.
γ振荡是感觉反应的一个稳定组成部分，但也是大脑背景自发活动的一部分。为了确定皮层中γ振荡的特性是否特定于其产生机制，我们在小鼠视觉皮层体内比较了感觉表征期间产生的振荡与无刺激时自发出现的振荡的层状结构和单神经元节律性。在麻醉（异氟烷和赛拉嗪）的小鼠视觉皮层中，视觉刺激触发的振荡主要在20至50赫兹之间，由于它们与高等哺乳动物中的γ振荡具有相似的功能意义，我们在此将其定义为γ范围。视觉皮层中的感觉表征特别增加了颗粒上层（L2/3）和颗粒层（L4）中的γ振荡幅度，并强烈带动颗粒下层中的假定兴奋性和抑制性神经元，而自发γ振荡均匀分布于皮层深度，并主要带动颗粒下层（L5/6）皮层中的假定抑制性神经元。两种不同条件下γ振荡的层状分布差异可能源于皮层兴奋性输入源的差异。此外，浅层γ振荡幅度的调制并未导致深层振荡的相应变化，这表明皮层的浅层和深层可能利用独立但相关的网络来产生γ振荡。这些结果表明，刺激驱动的γ振荡以不同于自发振荡的方式参与皮层回路，并提示皮层中存在多个产生γ振荡的网络。
