Kavli Institute for Systems Neuroscience, Center for Algorithms in the Cortex, Egil and Pauline Braathen and Fred Kavli Center for Cortical Microcircuits, Norwegian University of Science and Technology, Trondheim, Norway.
Eur J Neurosci. 2024 Jun;59(12):3236-3255. doi: 10.1111/ejn.16341. Epub 2024 Apr 21.
GABAergic neurons represent 10-15% of the neuronal population of the cortex but exert a powerful control over information flow in cortical circuits. The largest GABAergic class in the neocortex is represented by the parvalbumin-expressing fast-spiking neurons, which provide powerful somatic inhibition to their postsynaptic targets. Recently, the density of parvalbumin interneurons has been shown to be lower in associative areas of the mouse cortex as compared with sensory and motor areas. Modelling work based on these quantifications linked the low-density of parvalbumin interneurons with specific computations of associative cortices. However, it is still unknown whether the total GABAergic population of association cortices is smaller or whether another GABAergic type can compensate for the low density of parvalbumin interneurons. In the present study, we investigated these hypotheses using a combination of neuroanatomy, mouse genetics and neurophysiology. We found that the GABAergic population of association areas is comparable with that of primary sensory areas, and it is enriched of fast-spiking neurons that do not express parvalbumin and were not accounted for by previous quantifications. We developed an intersectional viral strategy to demonstrate that the population of fast-spiking neurons is comparable across cortical regions. Our results provide quantifications of the density of fast-spiking GABAergic neurons and offers new biological constrains to refine current models of cortical computations.
GABA 能神经元占皮质神经元总数的 10-15%，但对皮质回路中的信息流施加了强大的控制。新皮质中最大的 GABA 能神经元群是表达 Parvalbumin 的快速放电神经元，它们对其突触后靶标提供强大的体抑制。最近，与感觉和运动区相比，小鼠皮质的联合区中 Parvalbumin 中间神经元的密度较低。基于这些量化的建模工作将 Parvalbumin 中间神经元的低密度与联合皮质的特定计算联系起来。然而，目前尚不清楚关联皮质的总 GABA 能神经元群体是否较小，或者另一种 GABA 能神经元类型是否可以弥补 Parvalbumin 中间神经元的低密度。在本研究中，我们使用神经解剖学、小鼠遗传学和神经生理学的组合来研究这些假设。我们发现，联合区的 GABA 能神经元群体与初级感觉区相当，并且富含不表达 Parvalbumin 的快速放电神经元，而这些神经元在以前的量化中并未被考虑到。我们开发了一种交叉病毒策略来证明快速放电神经元在皮质区域之间的数量相当。我们的研究结果提供了快速放电 GABA 能神经元密度的定量，为细化当前皮质计算模型提供了新的生物学限制。
