Institute of Neuroscience and Medicine, INM-10, Research Centre Jülich, 52425 Jülich, Germany.
Department of Psychiatry, Psychotherapy and Psychosomatics, Medical School, RWTH Aachen University, 52074 Aachen, Germany.
Cereb Cortex. 2021 Aug 26;31(10):4533-4553. doi: 10.1093/cercor/bhab104.
Sparse population activity is a well-known feature of supragranular sensory neurons in neocortex. The mechanisms underlying sparseness are not well understood because a direct link between the neurons activated in vivo, and their cellular properties investigated in vitro has been missing. We used two-photon calcium imaging to identify a subset of neurons in layer L2/3 (L2/3) of mouse primary somatosensory cortex that are highly active following principal whisker vibrotactile stimulation. These high responders (HRs) were then tagged using photoconvertible green fluorescent protein for subsequent targeting in the brain slice using intracellular patch-clamp recordings and biocytin staining. This approach allowed us to investigate the structural and functional properties of HRs that distinguish them from less active control cells. Compared to less responsive L2/3 neurons, HRs displayed increased levels of stimulus-evoked and spontaneous activity, elevated noise and spontaneous pairwise correlations, and stronger coupling to the population response. Intrinsic excitability was reduced in HRs, while we found no evidence for differences in other electrophysiological and morphological parameters. Thus, the choice of which neurons participate in stimulus encoding may be determined largely by network connectivity rather than by cellular structure and function.
稀疏的群体活动是新皮层超颗粒感觉神经元的一个显著特征。稀疏的机制尚不清楚，因为在体内激活的神经元与在体外研究的细胞特性之间缺乏直接联系。我们使用双光子钙成像来鉴定小鼠初级体感皮层 L2/3 层（L2/3）中一组对主要胡须振动触觉刺激高度活跃的神经元。然后，这些高反应者（HRs）被光转化绿色荧光蛋白标记，以便在脑切片中使用细胞内膜片钳记录和生物胞嘧啶染色进行后续靶向。这种方法使我们能够研究 HRs 的结构和功能特性，这些特性将它们与不那么活跃的对照细胞区分开来。与反应性较低的 L2/3 神经元相比，HRs 表现出更高水平的刺激诱发和自发性活动、更高的噪声和自发性成对相关性，以及与群体反应更强的耦合。HRs 的内在兴奋性降低，而我们没有发现其他电生理和形态参数存在差异的证据。因此，决定哪些神经元参与刺激编码的选择可能主要取决于网络连接性，而不是细胞结构和功能。
