Mesik Lukas, Ma Wen-pei, Li Ling-yun, Ibrahim Leena A, Huang Z J, Zhang Li I, Tao Huizhong W
Zilkha Neurogenetic Institute, University of Southern California Los Angeles, CA, USA ; Neuroscience Graduate Program, University of Southern California Los Angeles, CA, USA.
Zilkha Neurogenetic Institute, University of Southern California Los Angeles, CA, USA.
Front Neural Circuits. 2015 May 22;9:22. doi: 10.3389/fncir.2015.00022. eCollection 2015.
Despite accounting for about 20% of all the layer 2/3 inhibitory interneurons, the vasoactive intestinal polypeptide (VIP) expressing neurons remain the least thoroughly studied of the major inhibitory subtypes. In recent studies, VIP neurons have been shown to be activated by a variety of cortico-cortical and neuromodulatory inputs, but their basic sensory response properties remain poorly characterized. We set out to explore the functional properties of layer 2/3 VIP neurons in the primary visual (V1) and primary auditory cortex (A1), using two-photon imaging guided patch recordings. We found that in the V1, VIP neurons were generally broadly tuned, with their sensory response properties resembling those of parvalbumin (PV) expressing neurons. With the exception of response latency, they did not exhibit a significant difference from PV neurons across any of the properties tested, including overlap index, response modulation, orientation selectivity, and direction selectivity. In the A1, on the other hand, VIP neurons had a strong tendency to be intensity selective, which is a property associated with a subset of putative pyramidal cells and virtually absent in PV neurons. VIP neurons had a best intensity that was significantly lower than that of PV and putative pyramidal neurons. Finally, sensory evoked spike responses of VIP neurons were delayed relative to pyramidal and PV neurons in both the V1 and A1. Combined, these results demonstrate that the sensory response properties of VIP neurons do not fit a simple model of being either PV-like broadly tuned or pyramidal-like narrowly tuned. Instead, the selectivity pattern varies with sensory area and can even be, as in the case of low sound intensity responsiveness, distinct from both PV and pyramidal neurons.
尽管表达血管活性肠肽（VIP）的神经元约占所有第2/3层抑制性中间神经元的20%，但它们仍是主要抑制性亚型中研究最少的。在最近的研究中，VIP神经元已被证明可被多种皮质-皮质和神经调节输入激活，但其基本的感觉反应特性仍未得到充分表征。我们利用双光子成像引导的膜片钳记录，探索初级视觉皮层（V1）和初级听觉皮层（A1）中第2/3层VIP神经元的功能特性。我们发现在V1中，VIP神经元通常具有广泛的调谐，其感觉反应特性类似于表达小白蛋白（PV）的神经元。除了反应潜伏期外，在包括重叠指数、反应调制、方向选择性和方向敏感性在内的任何测试特性方面，它们与PV神经元均无显著差异。另一方面，在A1中，VIP神经元有很强的强度选择性倾向，这是一种与一部分假定的锥体细胞相关的特性，而在PV神经元中几乎不存在。VIP神经元的最佳强度显著低于PV神经元和假定的锥体细胞。最后，在V1和A1中，VIP神经元的感觉诱发尖峰反应相对于锥体细胞和PV神经元均有延迟。综合来看，这些结果表明，VIP神经元的感觉反应特性并不符合简单的类似PV神经元那样广泛调谐或类似锥体细胞那样狭窄调谐的模型。相反，选择性模式随感觉区域而变化，甚至在低声强反应性的情况下，与PV神经元和锥体细胞都不同。
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