Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
Nat Commun. 2022 May 11;13(1):2585. doi: 10.1038/s41467-022-30349-w.
Information flow in the sensory cortex has been described as a predominantly feedforward sequence with deep layers as the output structure. Although recurrent excitatory projections from layer 5 (L5) to superficial L2/3 have been identified by anatomical and physiological studies, their functional impact on sensory processing remains unclear. Here, we use layer-selective optogenetic manipulations in the primary auditory cortex to demonstrate that feedback inputs from L5 suppress the activity of superficial layers regardless of the arousal level, contrary to the prediction from their excitatory connectivity. This suppressive effect is predominantly mediated by translaminar circuitry through intratelencephalic neurons, with an additional contribution of subcortical projections by pyramidal tract neurons. Furthermore, L5 activation sharpened tone-evoked responses of superficial layers in both frequency and time domains, indicating its impact on cortical spectro-temporal integration. Together, our findings establish a translaminar inhibitory recurrence from deep layers that sharpens feature selectivity in superficial cortical layers.
感觉皮层中的信息流被描述为主要是前馈序列，深层作为输出结构。尽管解剖学和生理学研究已经确定了来自第 5 层（L5）到浅层第 2/3 层的兴奋性回传投射，但它们对感觉处理的功能影响仍不清楚。在这里，我们使用初级听觉皮层中的层选择性光遗传学操作来证明，来自 L5 的反馈输入抑制了浅层的活动，而与它们的兴奋性连接相反，无论觉醒水平如何。这种抑制作用主要通过经脑内神经元的跨层回路介导，而锥体束神经元的皮质下投射也有一定的贡献。此外，L5 的激活在频率和时间域上锐化了浅层的音调诱发反应，表明其对皮质谱时整合的影响。总的来说，我们的发现确立了一种来自深层的跨层抑制性回传，它锐化了浅层皮质层的特征选择性。
