Massarelli Nicole, Yau Allan L, Hoffman Kathleen A, Kiemel Tim, Tytell Eric D
University of Maryland Baltimore County, Baltimore, USA.
Tufts University, Medford, USA.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2017 Oct;203(10):831-841. doi: 10.1007/s00359-017-1196-2. Epub 2017 Jul 12.
Proprioceptive sensory inputs are an integral part of the closed-loop system of locomotion. In the lamprey, a model organism for vertebrate locomotion, such sensory inputs come from intraspinal mechanosensory cells called "edge cells". These edge cells synapse directly onto interneurons in the spinal central pattern generator (CPG) circuit and allow the CPG to adjust the motor output according to how the body is bending. However, the encoding properties of the edge cells have never been fully characterized. To identify these properties and better understand edge cells' role in locomotion, we isolated spinal cords of silver lampreys (Ichthyomyzon unicuspis) and recorded extracellularly from the lateral tracts where edge cell axons are located. We identified cells that responded to mechanical stimuli and used standard spike sorting algorithms to identify separate units, then examined how the cells respond to bending rate and bending angle. Although some cells respond to the bending angle, as was previously known, the strongest and most common responses were to bending velocity. These encoding properties will help us better understand how lampreys and other basal vertebrates adapt their locomotor rhythms to different water flow patterns, perturbations, or other unexpected changes in their environments.
本体感觉输入是运动闭环系统的一个组成部分。在七鳃鳗（脊椎动物运动的一种模式生物）中，这种感觉输入来自脊髓内的机械感觉细胞，即“边缘细胞”。这些边缘细胞直接与脊髓中央模式发生器（CPG）回路中的中间神经元形成突触，并使CPG能够根据身体的弯曲方式调整运动输出。然而，边缘细胞的编码特性从未得到充分表征。为了确定这些特性并更好地理解边缘细胞在运动中的作用，我们分离了银七鳃鳗（Ichthyomyzon unicuspis）的脊髓，并在边缘细胞轴突所在的外侧束进行细胞外记录。我们识别出对机械刺激有反应的细胞，并使用标准的尖峰分类算法识别不同的单元，然后研究这些细胞如何对弯曲速率和弯曲角度做出反应。尽管如先前所知，一些细胞对弯曲角度有反应，但最强且最常见的反应是对弯曲速度的反应。这些编码特性将有助于我们更好地理解七鳃鳗和其他基础脊椎动物如何使它们的运动节律适应不同的水流模式、扰动或环境中的其他意外变化。
