Short-term dynamics of thalamocortical and intracortical synapses onto layer 6 neurons in neocortex
Short-term dynamics of thalamocortical and intracortical synapses onto layer 6 neurons in neocortex
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DOI：
10.1152/jn.2002.88.4.1924
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发表时间：
2002-10-01
影响因子：
2.5
通讯作者：
Connors, BW
中科院分区：
文献类型：
--
作者：
Beierlein, M;Connors, BW
第6层是新皮层连接回特定丘脑核团的主要来源。皮质丘脑（CT）系统在形成感觉输入中起着重要作用，但对产生CT活动的功能电路知之甚少。我们记录从两个主要类型的神经元在第6层，定期尖峰（RS;锥体神经元）和快速尖峰（FS;抑制性interneurons）细胞和不同的兴奋性输入的生理特性进行比较。丘脑刺激引起两个单突触输入具有不同的属性：怀疑丘脑皮质（TC）突触事件有短的lavage，短期突触抑制，和成对的脉冲反应，这表明低于正常的轴突传导。第二组突触反应可能起源于从丘脑逆向激活的CT细胞的皮质内侧支。这些皮层内反应具有较长的潜伏期，短时程突触易化，并通过轴突进行超常传导。怀疑TC输入FS细胞有显着较大的幅度比RS细胞。来自第6层相邻神经元的双重记录揭示了促进和抑制突触连接;抑制突触可能是由不投射到丘脑的第6层细胞形成的，因此没有通过丘脑刺激进行采样。我们的结论是，第6层神经元整合了各种输入与不同的时间动态，由突触前细胞类型。
Layer 6 is the main source of neocortical connections back to specific thalamic nuclei. Corticothalamic (CT) systems play an important role in shaping sensory input, but little is known about the functional circuitry that generates CT activity. We recorded from the two main types of neurons in layer 6, regular-spiking (RS; pyramidal neurons) and fast-spiking (FS; inhibitory interneurons) cells and compared the physiological properties of different excitatory inputs. Thalamic stimulation evoked two monosynaptic inputs with distinct properties: suspected thalamocortical (TC) synaptic events had short latencies, short-term synaptic depression, and paired-pulse responses that suggested subnormal axonal conduction. A second group of synaptic responses likely originated from intracortical collaterals of CT cells that were antidromically activated from the thalamus. These intracortical responses had longer latencies, short-term synaptic facilitation, and were transmitted by axons with supernormal conduction. Suspected TC inputs to FS cells had significantly larger amplitudes than those onto RS cells. Dual recordings from neighboring neurons in layer 6 revealed both facilitating and depressing synaptic connections; the depressing synapses were probably formed by layer 6 cells that do not project to the thalamus, and thus were not sampled by thalamic stimulation. We conclude that layer 6 neurons integrate a variety of inputs with distinct temporal dynamics that are determined by the presynaptic cell type.