Temprana Silvio G, Mongiat Lucas A, Yang Sung M, Trinchero Mariela F, Alvarez Diego D, Kropff Emilio, Giacomini Damiana, Beltramone Natalia, Lanuza Guillermo M, Schinder Alejandro F
Laboratory of Neuronal Plasticity, Leloir Institute-CONICET, Av. Patricias Argentinas 435, Buenos Aires, C1405BWE, Argentina.
Laboratory of Developmental Neurobiology, Leloir Institute-CONICET, Av. Patricias Argentinas 435, Buenos Aires, C1405BWE, Argentina.
Neuron. 2015 Jan 7;85(1):116-130. doi: 10.1016/j.neuron.2014.11.023. Epub 2014 Dec 18.
Developing granule cells (GCs) of the adult dentate gyrus undergo a critical period of enhanced activity and synaptic plasticity before becoming mature. The impact of developing GCs on the activity of preexisting dentate circuits remains unknown. Here we combine optogenetics, acute slice electrophysiology, and in vivo chemogenetics to activate GCs at different stages of maturation to study the recruitment of local target networks. We show that immature (4-week-old) GCs can efficiently drive distal CA3 targets but poorly activate proximal interneurons responsible for feedback inhibition (FBI). As new GCs transition toward maturity, they reliably recruit GABAergic feedback loops that restrict spiking of neighbor GCs, a mechanism that would promote sparse coding. Such inhibitory loop impinges only weakly in new cohorts of young GCs. A computational model reveals that the delayed coupling of new GCs to FBI could be crucial to achieve a fine-grain representation of novel inputs in the dentate gyrus.
成年齿状回中正在发育的颗粒细胞（GCs）在成熟之前会经历一个活动增强和突触可塑性增强的关键时期。发育中的颗粒细胞对已有齿状回路活动的影响尚不清楚。在这里，我们结合光遗传学、急性脑片电生理学和体内化学遗传学，在不同成熟阶段激活颗粒细胞，以研究局部靶网络的募集情况。我们发现，未成熟（4周龄）的颗粒细胞可以有效地驱动远端CA3靶标，但激活负责反馈抑制（FBI）的近端中间神经元的能力较差。随着新的颗粒细胞向成熟过渡，它们可靠地募集了GABA能反馈回路，这些回路限制了相邻颗粒细胞的放电，这是一种促进稀疏编码的机制。这种抑制性回路对年轻颗粒细胞的新群体影响较弱。一个计算模型表明，新的颗粒细胞与反馈抑制的延迟耦合对于在齿状回中实现新输入的精细表征可能至关重要。
