The Florey Institute of Neuroscience & Mental Health, University of Melbourne, Melbourne, Australia.
Division of Pulmonary, Critical Care & Sleep, Department of Medicine, Case Western Reserve University, Cleveland, USA.
J Physiol. 2020 Jun;598(11):2061-2079. doi: 10.1113/JP279605. Epub 2020 Apr 16.
The functional neuroanatomy of the mammalian respiratory network is far from being understood since experimental tools that measure neural activity across this brainstem-wide circuit are lacking. Here, we use silicon multi-electrode arrays to record respiratory local field potentials (rLFPs) from 196-364 electrode sites within 8-10 mm of brainstem tissue in single arterially perfused brainstem preparations with respect to the ongoing respiratory motor pattern of inspiration (I), post-inspiration (PI) and late-expiration (E2). rLFPs peaked specifically at the three respiratory phase transitions, E2-I, I-PI and PI-E2. We show, for the first time, that only the I-PI transition engages a brainstem-wide network, and that rLFPs during the PI-E2 transition identify a hitherto unknown role for the dorsal respiratory group. Volumetric mapping of pontomedullary rLFPs in single preparations could become a reliable tool for assessing the functional neuroanatomy of the respiratory network in health and disease.
While it is widely accepted that inspiratory rhythm generation depends on the pre-Bötzinger complex, the functional neuroanatomy of the neural circuits that generate expiration is debated. We hypothesized that the compartmental organization of the brainstem respiratory network is sufficient to generate macroscopic local field potentials (LFPs), and if so, respiratory (r) LFPs could be used to map the functional neuroanatomy of the respiratory network. We developed an approach using silicon multi-electrode arrays to record spontaneous LFPs from hundreds of electrode sites in a volume of brainstem tissue while monitoring the respiratory motor pattern on phrenic and vagal nerves in the perfused brainstem preparation. Our results revealed the expression of rLFPs across the pontomedullary brainstem. rLFPs occurred specifically at the three transitions between respiratory phases: (1) from late expiration (E2) to inspiration (I), (2) from I to post-inspiration (PI), and (3) from PI to E2. Thus, respiratory network activity was maximal at respiratory phase transitions. Spatially, the E2-I, and PI-E2 transitions were anatomically localized to the ventral and dorsal respiratory groups, respectively. In contrast, our data show, for the first time, that the generation of controlled expiration during the post-inspiratory phase engages a distributed neuronal population within ventral, dorsal and pontine network compartments. A group-wise independent component analysis demonstrated that all preparations exhibited rLFPs with a similar temporal structure and thus share a similar functional neuroanatomy. Thus, volumetric mapping of rLFPs could allow for the physiological assessment of global respiratory network organization in health and disease.
哺乳动物呼吸网络的功能神经解剖学远未被理解，因为缺乏测量整个脑干范围内神经活动的实验工具。在这里，我们使用硅质多电极阵列，在单动脉灌注的脑干标本中，在与吸气（I）、后吸气（PI）和后期呼气（E2）持续呼吸运动模式相对应的 8-10 毫米的脑干组织内，从 196-364 个电极位点记录呼吸局部场电位（rLFPs）。rLFPs 专门在三个呼吸相位转换时达到峰值，即 E2-I、I-PI 和 PI-E2。我们首次表明，只有 I-PI 转换会激活整个脑干网络，而在 PI-E2 转换期间的 rLFPs 表明背侧呼吸组具有未知的作用。在单个标本中对桥脑延髓 rLFPs 进行容积映射可能成为评估健康和疾病中呼吸网络功能神经解剖学的可靠工具。
虽然吸气节律的产生广泛认为依赖于 Pre-Bötzinger 复合体，但产生呼气的神经回路的功能神经解剖学仍存在争议。我们假设脑干呼吸网络的分区组织足以产生宏观局部场电位（LFPs），如果是这样，呼吸（r）LFPs 可用于绘制呼吸网络的功能神经解剖图。我们开发了一种使用硅质多电极阵列的方法，在灌注的脑干标本中，在监测膈神经和迷走神经呼吸运动模式的同时，从脑干组织的数百个电极位点记录自发 LFPs。我们的结果揭示了 pontomedullary 脑干内 rLFPs 的表达。rLFPs 专门在三个呼吸相位之间的转换时出现：（1）从后期呼气（E2）到吸气（I），（2）从 I 到后吸气（PI），和（3）从 PI 到 E2。因此，呼吸网络活动在呼吸相位转换时达到最大值。从空间上看，E2-I 和 PI-E2 转换分别定位于腹侧和背侧呼吸组。相比之下，我们的数据首次表明，在后吸气期期间进行的受控呼气的产生涉及腹侧、背侧和桥脑网络隔室内的分布式神经元群体。组间独立成分分析表明，所有标本均表现出具有相似时间结构的 rLFPs，因此具有相似的功能神经解剖学。因此，rLFPs 的容积映射可以对健康和疾病中的全球呼吸网络组织进行生理评估。
