Meng Hui, Laurens Jean, Blázquez Pablo M, Angelaki Dora E
Department of Neuroscience, Baylor College of Medicine, Houston, TX, 77030, USA.
J Physiol. 2015 Jan 1;593(1):321-30. doi: 10.1113/jphysiol.2014.278523. Epub 2014 Nov 17.
We quantify both spontaneous and stimulus-driven responses of interneurons in lobules X (nodulus) and IXc,d (ventral uvula) of the caudal vermis during vestibular stimulation. Based on baseline firing, at least three types of neuronal populations could be distinguished. First, there was a group of very regular firing neurons with high mean discharge rates. Second, there was a group of low firing neurons with a range of discharge regularity. Third, we also encountered putative interneurons with discharge regularity and mean firing rates that were indistinguishable from those of physiologically identified Purkinje cells. The vestibular responses of putative interneurons were generally similar to those of Purkinje cells, thus encoding tilt, translation or mixtures of these signals. Mossy fibres showed unprocessed, otolith afferent-like properties. The cerebellar cortex is among the brain's most well-studied circuits and includes distinct classes of excitatory and inhibitory interneurons. Several studies have attempted to characterize the in vivo properties of cerebellar interneurons, yet little is currently known about their stimulus-driven properties. Here we quantify both spontaneous and stimulus-driven responses of interneurons in lobules X (nodulus) and IXc,d (ventral uvula) of the macaque caudal vermis during vestibular stimulation. Interneurons were identified as cells located >100 μm from the Purkinje cell layer that did not exhibit complex spikes. Based on baseline firing, three types of interneurons could be distinguished. First, there was a group of very regular firing interneurons with high mean discharge rates, which consistently encoded tilt, rather than translational head movements. Second, there was a group of low firing interneurons with a range of discharge regularity. This group had more diverse vestibular properties, where most were translation-selective and a few tilt- or gravitoinertial acceleration-selective. Third, we also encountered interneurons that were similar to Purkinje cells in terms of discharge regularity and mean firing rate. This group also encoded mixtures of tilt and translation signals. A few mossy fibres showed unprocessed, otolith afferent-like properties, encoding the gravitoinertial acceleration. We conclude that tilt- and translation-selective signals, which reflect neural computations transforming vestibular afferent information, are not only encountered in Purkinje cell responses. Instead, upstream interneurons within the cerebellar cortex are also characterized by similar properties, thus implying a widespread network computation.
我们对猕猴尾状蚓小叶X（小结）和IXc、d（腹侧小舌）中中间神经元的自发反应和刺激驱动反应进行了量化，这些反应发生在前庭刺激期间。基于基线放电情况，可区分出至少三种类型的神经元群体。首先，有一组放电非常规律、平均放电率较高的神经元。其次，有一组放电率较低、放电规律各异的神经元。第三，我们还遇到了一些推定的中间神经元，它们的放电规律和平均放电率与生理上鉴定出的浦肯野细胞无法区分。推定中间神经元的前庭反应通常与浦肯野细胞相似，因此编码倾斜、平移或这些信号的混合。苔藓纤维表现出未经处理的、类似耳石传入的特性。小脑皮质是大脑中研究最深入的神经回路之一，包含不同类型的兴奋性和抑制性中间神经元。几项研究试图描述小脑中间神经元的体内特性，但目前对其刺激驱动特性知之甚少。在此，我们对猕猴尾状蚓小叶X（小结）和IXc、d（腹侧小舌）中中间神经元在前庭刺激期间的自发反应和刺激驱动反应进行了量化。中间神经元被确定为距离浦肯野细胞层大于100μm且不表现出复合锋电位的细胞。基于基线放电情况，可区分出三种类型的中间神经元。首先，有一组放电非常规律、平均放电率较高的中间神经元，它们始终编码倾斜，而不是头部平移运动。其次，有一组放电率较低、放电规律各异的中间神经元。这一组的前庭特性更为多样，其中大多数对平移有选择性，少数对倾斜或重力惯性加速度有选择性。第三，我们还遇到了一些在放电规律和平均放电率方面与浦肯野细胞相似的中间神经元。这一组也编码倾斜和平移信号的混合。少数苔藓纤维表现出未经处理的、类似耳石传入的特性，编码重力惯性加速度。我们得出结论，反映转化前庭传入信息的神经计算的倾斜和平移选择性信号，不仅在浦肯野细胞反应中出现。相反，小脑皮质内的上游中间神经元也具有类似特性，因此意味着存在广泛的网络计算。
