Thalamic control of layer 1 circuits in prefrontal cortex.
Thalamic control of layer 1 circuits in prefrontal cortex.
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前额叶皮层中第1层电路的丘脑控制。
DOI：
10.1523/jneurosci.3231-12.2012
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发表时间：
2012-12-05
期刊：
影响因子：
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通讯作者：
Connors BW
中科院分区：
文献类型：
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作者：
Cruikshank SJ;Ahmed OJ;Stevens TR;Patrick SL;Gonzalez AN;Elmaleh M;Connors BW
丘脑皮质（TC）加工的知识主要来自对投射到初级感觉皮质中间层的核心丘脑系统的研究。然而，大多数丘脑中继神经元由“非特异性”丘脑核中最密集的细胞基质组成，通常是多个皮质区域的靶层1。一个长期存在的假设是，在改变行为状态时，基质TC系统对调节新皮层的兴奋性至关重要，但我们对这种调节的机制几乎一无所知。目前还不清楚的是，为核心感觉TC系统建立的突触和电路机制是否适用于矩阵TC系统。本文描述了利用光遗传学和体外电生理技术研究丘脑基质对小鼠前额皮质的影响。通道视紫红质-2在丘脑中线和副线（基质）神经元中表达，其第1层投射的TC轴突被光学激活。与传统观点相反，我们发现矩阵TC投射到第一层可以传输相对强、快、高保真的突触信号。第1层TC投射优先驱动第1层的抑制性中间神经元，尤其是后尖峰亚型的抑制性中间神经元，并且经常触发第1层中间神经元和第2/3层锥体细胞的前馈抑制。在重复刺激时，基质的反应比核心感觉TC通路的反应持续得多。因此，矩阵TC电路似乎专门用于相对较长时间内的稳健传输，这与在工作记忆中观察到的持续激活类型一致，并且可能适用于状态依赖性兴奋性调节。
Knowledge of thalamocortical (TC) processing comes mainly from studying core thalamic systems that project to middle layers of primary sensory cortices. However, most thalamic relay neurons comprise a matrix of cells that are densest in the “nonspecific” thalamic nuclei and usually target layer 1 of multiple cortical areas. A longstanding hypothesis is that matrix TC systems are crucial for regulating neocortical excitability during changing behavioral states, yet we know almost nothing about the mechanisms of such regulation. It is also unclear whether synaptic and circuit mechanisms that are well established for core sensory TC systems apply to matrix TC systems. Here we describe studies of thalamic matrix influences on mouse prefrontal cortex using optogenetic and in vitro electrophysiology techniques. Channelrhodopsin-2 was expressed in midline and paralaminar (matrix) thalamic neurons, and their layer 1-projecting TC axons were activated optically. Contrary to conventional views, we found that matrix TC projections to layer 1 could transmit relatively strong, fast, high-fidelity synaptic signals. Layer 1 TC projections preferentially drove inhibitory interneurons of layer 1, especially those of the late-spiking subtype, and often triggered feedforward inhibition in both layer 1 interneurons and pyramidal cells of layers 2/3. Responses during repetitive stimulation were far more sustained for matrix than for core sensory TC pathways. Thus, matrix TC circuits appear to be specialized for robust transmission over relatively extended periods, consistent with the sort of persistent activation observed during working memory and potentially applicable to state-dependent regulation of excitability.