Department of Molecular and Cellular Biology, University of California Berkeley, Berkeley, CA 94720, USA; Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA 94720, USA.
Neuron. 2013 Oct 2;80(1):210-22. doi: 10.1016/j.neuron.2013.07.026.
Local recurrent networks in neocortex are critical nodes for sensory processing, but their regulation by experience is much less understood than for long-distance (translaminar or cross-columnar) projections. We studied local L2/3 recurrent networks in rat somatosensory cortex during deprivation-induced whisker map plasticity, by expressing channelrhodopsin-2 (ChR2) in L2/3 pyramidal cells and measuring light-evoked synaptic currents in ex vivo S1 slices. In columns with intact whiskers, brief light impulses evoked recurrent excitation and supralinear inhibition. Deprived columns showed modestly reduced excitation and profoundly reduced inhibition, providing a circuit locus for disinhibition of whisker-evoked responses observed in L2/3 in vivo. Slower light ramps elicited sustained gamma frequency oscillations, which were nearly abolished in deprived columns. Reduction in gamma power was also observed in spontaneous LFP oscillations in L2/3 of deprived columns in vivo. Thus, L2/3 recurrent networks are a powerful site for homeostatic modulation of excitation-inhibition balance and regulation of gamma oscillations.
局部皮层内的反馈网络是感觉处理的关键节点，但它们的经验调节比远距离（跨层或跨柱）投射的调节了解得少得多。我们通过在 L2/3 锥体神经元中表达通道型视蛋白-2（ChR2），并在离体 S1 切片中测量光诱发的突触电流，研究了感觉皮层中局部 L2/3 反馈网络在剥夺诱导的胡须图可塑性期间的活动。在有完整胡须的柱中，短暂的光脉冲会引发反馈兴奋和超线性抑制。剥夺柱显示出兴奋适度减少和抑制显著减少，为在 L2/3 中观察到的胡须诱发反应的去抑制提供了一个回路位置。较慢的光斜坡引发持续的伽马频率振荡，在剥夺柱中几乎被消除。在剥夺柱中，自发 LFP 振荡的伽马功率也减少。因此，L2/3 反馈网络是一种强大的机制，可用于调节兴奋-抑制平衡的同型调节和伽马振荡的调节。
