The cutaneous code: breaking down neural patterns and optimal noise

从脚输入的皮肤减少会导致身体位置感(本体感觉)的缺陷，以及控制平衡的肌肉反射的下降。增加皮肤输入的努力有几种形式，主要是振动或电刺激来增强皮肤输入(随机共振；SR)。到目前为止，SR振动技术已经使用了很大范围的频率来定位驻留在皮肤中的所有四种皮肤机械感受器(慢适应；SA和快速适应FA，类型I和II)。然而，我们实验室的工作表明，从特定的传入亚类(SA I型和FA I型)到手臂和腿部的运动神经元有更强的反射联系，这表明这些机械感受器可能在平衡控制中发挥更大的作用。因此，集中SR频率以实现这些相关亚类的靶向受体激活将更加有效。*第一个重要的步骤是确定哪些受体在自然运动过程中被激活。在该提案的第一个目标中，我们将确定皮肤在自然载荷和剪切作用下的基本激发特性。这个项目扩展了我们最近的工作，我们检查了单个感受器的激发到孤立的振动频率，这是真实输入的组成部分。这项先前的工作旨在更好地了解如何最好地激活单个受体亚类。通过了解哪些受体对自然负荷做出反应，我们可以针对这些受体来增强感觉反馈。*该提案的第二个目标是使用流线型SR产生选定的机械感受器的单独激活。在我们之前的工作中，我们已经证明了足部皮肤中的SA和FA受体具有特定的频段，它们最容易被激活。目标2将确定改进的频段(频率有限)是否能够实现特定受体的靶向激活。专门的SR可能有能力通过靶向与运动和平衡控制相关的个别皮肤受体来改善平衡结果。*最后，我们承认，皮肤感受器，特别是脚上的感受器，在自然运动过程中并不是孤立地被激活的。我们的目标是在我们的工作中增强特定的受体，因此有必要了解这些受体如何协同工作来提供密码。第三个目标将研究受体亚类之间的兴奋性和抑制性联系，以帮助优化感觉激活。*这项工作将共同识别皮肤中的特定受体，我们可以针对这些受体来增强感觉反馈。在隔离状态下选择性地增强皮肤受体的能力，将使与平衡控制最相关的受体的反馈得到增强。这项工作还可以促进当前鞋垫技术的进步，改善假肢用户的感觉界面，并有助于导航设备(游戏、军事)的发展。

Reduced skin input from the feet causes deficits in the sense of body position (proprioception) and declines in the muscular reflexes that control balance. Efforts to augment skin input have taken on several forms, primarily vibration or electrical stimulation to enhance skin input (stochastic resonance; SR). To date, SR vibration technologies have used a large range of frequencies to target all four of the cutaneous mechanoreceptors that reside in the skin (Slow adapting; SA and Fast Adapting FA, type I and II). However, work in our lab has shown there are stronger reflex connections from specific subclasses of afferents (SA type I and FA type I) to motor neurons of the arms and legs, suggesting these mechanoreceptors may have a larger role in balance control. As a result, it would be more effective to focus SR frequencies to enable targeted receptor activation of these relevant subclasses. ******The first important step is to identify which receptors are activated during natural movements. In the first Aim of the proposal we will identify the fundamental firing characteristics of skin in response to natural load and shear. This project extends our recent work where we examined individual receptor firing to isolated vibration frequencies, which are components of real input. This previous work aimed to better understand how to best activate individual receptor subclasses. By understanding which receptors respond to natural load we can target these receptors to enhance sensory feedback. ******The second Aim of the proposal is to generate isolated activation of select mechanoreceptors using streamlined SR. In our previous work we have shown that SA and FA receptors in the foot skin have specific frequency bands to which they are most easily activated. Aim 2 will establish whether refined frequency bands (with limited frequencies) will enable targeted activation of specific receptors. Specialized SR may have the ability to improve balance outcomes by targeting individual skin receptors that are relevant for movement and balance control. ******Finally, we acknowledge that skin receptors, particularly on the feet, are not activated in isolation during natural movement. We aim to enhance specific receptors in our work, and as such it is necessary to understand how the receptors work together to provide the code. The third Aim will examine the excitatory and inhibitory connections between receptor subclasses to help optimize sensory activation. ******Together this work will identify specific receptors in the skin that we can target for enhanced sensory feedback. The ability to selectively enhance skin receptors in isolation will enable augmented feedback from receptors that are most relevant for balance control. This work can also contribute to the advancement of current insole technologies, improve the sensory interface for prosthetic users, and contribute to the development of navigation devices (gaming, military).