Department of Organismal Biology and Anatomy and Committee on Computational Neuroscience, University of Chicago, Chicago, IL 60637.
Proc Natl Acad Sci U S A. 2013 Oct 15;110(42):17107-12. doi: 10.1073/pnas.1305509110. Epub 2013 Sep 30.
When we run our fingers over the surface of an object, we acquire information about its microgeometry and material properties. Texture information is widely believed to be conveyed in spatial patterns of activation evoked across one of three populations of cutaneous mechanoreceptive afferents that innervate the fingertips. Here, we record the responses evoked in individual cutaneous afferents in Rhesus macaques as we scan a diverse set of natural textures across their fingertips using a custom-made rotating drum stimulator. We show that a spatial mechanism can only account for the processing of coarse textures. Information about most natural textures, however, is conveyed through precise temporal spiking patterns in afferent responses, driven by high-frequency skin vibrations elicited during scanning. Furthermore, these texture-specific spiking patterns predictably dilate or contract in time with changes in scanning speed; the systematic effect of speed on neuronal activity suggests that it can be reversed to achieve perceptual constancy across speeds. The proposed temporal coding mechanism involves converting the fine spatial structure of the surface into a temporal spiking pattern, shaped in part by the mechanical properties of the skin, and ascribes an additional function to vibration-sensitive mechanoreceptive afferents. This temporal mechanism complements the spatial one and greatly extends the range of tangible textures. We show that a combination of spatial and temporal mechanisms, mediated by all three populations of afferents, accounts for perceptual judgments of texture.
当我们用手指触摸物体表面时，我们会获取有关其微观几何形状和材料特性的信息。纹理信息被广泛认为是通过三种支配指尖的皮肤机械感受器传入纤维群体之一的激活空间模式来传递的。在这里，我们使用定制的旋转鼓刺激器在恒河猴的指尖上扫描各种自然纹理，记录单个皮肤传入纤维的反应。我们表明，空间机制只能解释粗纹理的处理。然而，大多数自然纹理的信息是通过传入反应中的精确时间尖峰模式来传递的，这是由扫描过程中产生的高频皮肤振动驱动的。此外，这些纹理特定的尖峰模式随着扫描速度的变化可预测地在时间上扩张或收缩；速度对神经元活动的系统影响表明，它可以被反转以实现速度之间的知觉恒常性。所提出的时间编码机制涉及将表面的精细空间结构转换为时间尖峰模式，部分由皮肤的机械特性形成，并赋予振动敏感的机械感受器传入纤维额外的功能。这种时间机制补充了空间机制，并大大扩展了可触知纹理的范围。我们表明，由三种传入纤维群体介导的空间和时间机制的组合解释了对纹理的知觉判断。
