Constraints on the deformation of the vibrissa within the follicle.
Constraints on the deformation of the vibrissa within the follicle.
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DOI：
10.1371/journal.pcbi.1007887
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发表时间：
2021-04
影响因子：
4.3
通讯作者：
Hartmann MJZ
中科院分区：
文献类型：
--
作者：
Luo Y;Bresee CS;Rudnicki JW;Hartmann MJZ
几乎所有的哺乳动物都有一个专门用于触觉的触觉系统，由皮肤中富有传感器的毛囊长出的胡须组成。当胡须偏向物体时，它会在毛囊内变形，并对里面的机械感受器施加力。此外，在活跃的搅拌行为中，毛囊周围的肌肉收缩和环状窦内血压的增加将影响胡须的变形轮廓。然而，到目前为止，还不可能在实验上测量胡须在完整的毛囊中如何变形，或者它对不同组机械感受器的影响。本研究开发了一种新的模型来预测毛囊窦复合体内的振动变形。该模型基于先前对毛囊内胡须变形的体外研究的实验结果，以及对毛囊组织的新的组织学分析。然后，它用于模拟被动触摸和主动搅拌过程中毛囊内的胡须变形。结果表明，最有可能的胡须变形轮廓是“S形”，横跨卵泡的中线，正好在环状窦的正下方。主动扭动的模拟表明，整体肌肉硬度的增加，深层和浅层固有肌肉硬度比率的增加，以及鼻窦血压的增加，都会增强触觉敏感度。最后，我们讨论了形变轮廓如何映射到每种机械感受器类型的初级传入的反应。本研究中提出的力学模型是模拟胡须毛囊内机械相互作用的重要第一步。许多哺乳动物依靠胡须作为触觉的一种模式，特别是在黑暗中探索时。在许多胡须专家动物中，可以观察到胡须活跃的、有节奏的伸展和回缩，通常被称为“搅拌”。在基于胡须的传感过程中，外部刺激产生的力和力矩被传递到毛囊内须轴的底部。在毛囊内，胡须的变形和周围组织之间的相互作用决定了不同组的机械感受器将如何变形，从而将机械信号转换为电信号。然而，目前还不可能在体内对这种相互作用进行实验测量。因此，我们创建了一个毛囊窦复合体的力学模型，以模拟毛囊内因外部胡须偏转而导致的胡须变形。我们的结果提供了第一次对胡须形状的估计，因为它在毛囊中变形，在被动触摸和主动搅拌期间。反过来，这些形状估计使我们能够预测胡须将如何在毛囊内不同位置的不同类型的机械感受器的作用下变形。此外，我们发现内在肌肉收缩和血压升高都会提高胡须系统的触觉敏感度。
Nearly all mammals have a vibrissal system specialized for tactile sensation, composed of whiskers growing from sensor-rich follicles in the skin. When a whisker deflects against an object, it deforms within the follicle and exerts forces on the mechanoreceptors inside. In addition, during active whisking behavior, muscle contractions around the follicle and increases in blood pressure in the ring sinus will affect the whisker deformation profile. To date, however, it is not yet possible to experimentally measure how the whisker deforms in an intact follicle or its effects on different groups of mechanoreceptors. The present study develops a novel model to predict vibrissal deformation within the follicle sinus complex. The model is based on experimental results from a previous ex vivo study on whisker deformation within the follicle, and on a new histological analysis of follicle tissue. It is then used to simulate whisker deformation within the follicle during passive touch and active whisking. Results suggest that the most likely whisker deformation profile is “S-shaped,” crossing the midline of the follicle right below the ring sinus. Simulations of active whisking indicate that an increase in overall muscle stiffness, an increase in the ratio between deep and superficial intrinsic muscle stiffness, and an increase in sinus blood pressure will all enhance tactile sensitivity. Finally, we discuss how the deformation profiles might map to the responses of primary afferents of each mechanoreceptor type. The mechanical model presented in this study is an important first step in simulating mechanical interactions within whisker follicles. Many mammals rely on whiskers as a mode of tactile sensation, especially when exploring in darkness. Active, rhythmic protraction and retraction of the whiskers, commonly referred to as “whisking,” is observed among many whisker specialist animals. During whisker-based sensing, forces and moments generated by external stimuli are transmitted to the base of the whisker shaft inside the follicle. Within the follicle, the interaction between the whisker’s deformation and the surrounding tissue determines how different groups of mechanoreceptors will deform, thereby transducing the mechanical signals into electrical signals. However, it is not yet possible to experimentally measure this interaction in vivo. We therefore created a mechanical model of the follicle sinus complex to simulate whisker deformation within the follicle resulting from external whisker deflection. Our results provide the first estimate of whisker shape as it deforms in the follicle, during both passive touch and active whisking. In turn, these shape estimates allow us to predict how the whisker will deform against different types of mechanoreceptors at different locations within the follicle. In addition, we find that both intrinsic muscle contraction and an increase in blood pressure will improve the tactile sensitivity of the whisker system.
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