Groupe de recherche sur le système nerveux central (GRSNC) and Département de physiologie, Faculté de médecine, Université de Montréal, Montreal, Quebec, Canada; and.
J Neurophysiol. 2013 Oct;110(7):1554-66. doi: 10.1152/jn.00675.2012. Epub 2013 Jul 10.
Moving stimuli activate all of the mechanoreceptive afferents involved in discriminative touch, but their signals covary with several parameters, including texture. Despite this, the brain extracts precise information about tactile speed, and humans can scale the tangential speed of moving surfaces as long as they have some surface texture. Speed estimates, however, vary with texture: lower estimates for rougher surfaces (increased spatial period, SP). We hypothesized that the discharge of cortical neurons playing a role in scaling tactile speed should covary with speed and SP in the same manner. Single-cell recordings (n = 119) were made in the hand region of primary somatosensory cortex (S1) of awake monkeys while raised-dot surfaces (longitudinal SPs, 2-8 mm; periodic or nonperiodic) were displaced under their fingertips at speeds of 40-105 mm/s. Speed sensitivity was widely distributed (area 3b, 13/25; area 1, 32/51; area 2, 31/43) and almost invariably combined with texture sensitivity (82% of cells). A subset of cells (27/64 fully tested speed-sensitive cells) showed a graded increase in discharge with increasing speed for testing with both sets of surfaces (periodic, nonperiodic), consistent with a role in tactile speed scaling. These cells were almost entirely confined to caudal S1 (areas 1 and 2). None of the speed-sensitive cells, however, showed a pattern of decreased discharge with increased SP, as found for subjective speed estimates in humans. Thus further processing of tactile motion signals, presumably in higher-order areas, is required to explain human tactile speed scaling.
移动刺激会激活参与辨别触摸的所有机械感受传入纤维，但它们的信号与几个参数相关，包括纹理。尽管如此，大脑还是会提取出关于触觉速度的精确信息，人类可以根据移动表面的切向速度进行缩放，只要它们具有一定的表面纹理。然而，速度估计值会随纹理而变化：较粗糙的表面（增加空间周期，SP）估计值较低。我们假设在进行触觉速度缩放时起作用的皮质神经元的放电应该以与速度和 SP 相同的方式相关。在清醒猴子的初级体感皮层（S1）手部区域进行单细胞记录（n = 119），同时在指尖下移动凸起点表面（纵向 SP，2-8 毫米；周期性或非周期性），速度为 40-105 毫米/秒。速度敏感性广泛分布（3b 区，13/25；1 区，32/51；2 区，31/43），几乎总是与纹理敏感性相结合（82%的细胞）。一组细胞（27/64 个经过充分测试的对速度敏感的细胞）显示出随着测试表面（周期性、非周期性）的速度增加而放电逐渐增加的模式，这与在触觉速度缩放中起作用的模式一致。这些细胞几乎完全局限于 S1 的尾部（1 区和 2 区）。然而，没有一个速度敏感的细胞表现出放电随 SP 增加而减少的模式，这与人类对主观速度的估计一致。因此，需要进一步处理触觉运动信号，大概是在更高阶的区域，以解释人类的触觉速度缩放。
