Department of Neurobiology and Anatomy, University of Rochester School of Medicine, Box 603, 601 Elmwood Ave, Rochester, NY 14642, USA.
J Neurophysiol. 2010 Jun;103(6):3001-16. doi: 10.1152/jn.01053.2009. Epub 2010 Apr 7.
Our goal is to examine the relationship between neuron- and network-level processing in the context of a well-studied cortical function, the processing of thalamic input by whisker-barrel circuits in rodent neocortex. Here we focus on neuron-level processing and investigate the responses of excitatory and inhibitory barrel neurons to simulated thalamic inputs applied using the dynamic clamp method in brain slices. Simulated inputs are modeled after real thalamic inputs recorded in vivo in response to brief whisker deflections. Our results suggest that inhibitory neurons require more input to reach firing threshold, but then fire earlier, with less variability, and respond to a broader range of inputs than do excitatory neurons. Differences in the responses of barrel neuron subtypes depend on their intrinsic membrane properties. Neurons with a low input resistance require more input to reach threshold but then fire earlier than neurons with a higher input resistance, regardless of the neuron's classification. Our results also suggest that the response properties of excitatory versus inhibitory barrel neurons are consistent with the response sensitivities of the ensemble barrel network. The short response latency of inhibitory neurons may serve to suppress ensemble barrel responses to asynchronous thalamic input. Correspondingly, whereas neurons acting as part of the barrel circuit in vivo are highly selective for temporally correlated thalamic input, excitatory barrel neurons acting alone in vitro are less so. These data suggest that network-level processing of thalamic input in barrel cortex depends on neuron-level processing of the same input by excitatory and inhibitory barrel neurons.
我们的目标是在一个研究充分的皮质功能背景下，研究神经元和网络水平处理之间的关系，该功能为啮齿动物新皮层中触须-桶状结构对丘脑输入的处理。这里我们关注神经元水平的处理，并研究使用脑片动态钳位方法施加模拟丘脑输入时兴奋性和抑制性桶状神经元的反应。模拟输入是根据在体内记录的真实丘脑输入进行建模的，这些输入是对短暂触须偏转的反应。我们的结果表明，抑制性神经元需要更多的输入才能达到放电阈值，但随后更早地放电，变异性更小，并且对更广泛的输入范围作出反应，而兴奋性神经元则不然。桶状神经元亚型反应的差异取决于其内在的膜特性。具有低输入电阻的神经元需要更多的输入才能达到阈值，但随后比具有高输入电阻的神经元更早地放电，而与神经元的分类无关。我们的结果还表明，兴奋性与抑制性桶状神经元的反应特性与桶状网络的整体反应灵敏度一致。抑制性神经元的短反应潜伏期可能有助于抑制桶状网络对异步丘脑输入的反应。相应地，虽然在体内作为桶状回路一部分的神经元对时间相关的丘脑输入具有高度选择性，但在体外单独作用的兴奋性桶状神经元则不然。这些数据表明，桶状皮质中丘脑输入的网络水平处理依赖于兴奋性和抑制性桶状神经元对相同输入的神经元水平处理。
