Simulation of motion on the skin. III. Mechanisms used by rapidly adapting cutaneous mechanoreceptors in the primate hand for spatiotemporal resolution and two-point discrimination.
Simulation of motion on the skin. III. Mechanisms used by rapidly adapting cutaneous mechanoreceptors in the primate hand for spatiotemporal resolution and two-point discrimination.
复制标题
模拟皮肤上的运动。
DOI：
10.1152/jn.1990.63.4.841
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发表时间：
1990
影响因子：
2.5
通讯作者：
Palmer,CI
中科院分区：
文献类型：
--
作者：
Gardner,EP;Palmer,CI
1. 快速适应（RA）机械感受器的贡献两点辨别已被评估通过检查他们的能力来解决光栅模式的间距在皮肤上转移。实验测试了两种不同的神经编码机制，这些机制被认为是手部空间细节分辨率的基础：1)一种速率强度编码，其中表面特征的间距由单个感觉传入信号的平均发射频率编码；2)一种形状同构表示，其中单个传入信号的发射模式的变化反映了皮肤凹陷的时空特征。2. 为了测量支配猕猴手部的RA机械感受器的空间灵敏度，我们在放置在无毛皮肤上的计算机控制的OPTACON刺激器上显示一对相距1-13毫米的水平条。两点分辨率是通过同时以100,50和25hz的频率脉冲对行来测量的；为了模拟横向运动，每对手都被串联起来移动。单纤维记录麻醉猴子的类风湿性关节炎传入事件。3. 感受野直径似乎是两个杆间间隙空间分辨率的关键决定因素。如果条间距小于字段直径，则RAs连续发射，但当两个活动行都包含在字段中时，ra不会对输入求和。假设重叠输入与最强的神经元控制轴突输出之间的闭塞，可以从单神经元曲线中预测间隔小于4.8 mm的两个神经元所引起的响应曲线。三分之二被测试的RAs放电1个脉冲，当条形图案穿过电场时，产生一个均匀的脉冲序列，其频率反映刺激脉冲率，但无法显示条形图案之间的间隙。另外有17%的射孔管在射孔棒接触或跨越场地中心时发射2个尖峰/脉冲，但也无法区分间距小于3.6 mm的单个条纹。4. 只有17%的RAs表示的间隙小于场直径。这些纤维对间隔至少2.4 mm的条形图表现出双峰响应曲线，发射2个尖峰/脉冲作为第一个脉冲，然后第二个条纹穿过场中心。峰值之间的时间对应于杆间距。当相邻的条跨越场中心时，响应的幅度减小，因为同时输入之间的遮挡阻止了两个刺激的输入之和。16个RAs中有15个无法分辨间距为1.2 mm的条纹，因为双尖峰反应仅由前导条纹引起。（摘要删节为400字）
1. The contribution of rapidly adapting (RA) mechanoreceptors to two-point discrimination has been evaluated by examining their ability to resolve the spacing of grating patterns shifted across the skin. The experiments test two different neural coding mechanisms that have been proposed to underlie resolution of spatial detail on the hand: 1) a rate-intensity code in which the spacing of surface features is encoded by the average frequency of firing of individual sensory afferents, and 2) an isomorphic representation of shape in which variations in the firing patterns of individual afferents reflect the spatiotemporal profile of skin indentation. 2. To measure the spatial acuity of RA mechanoreceptors innervating the hands of macaque monkeys, we displayed pairs of horizontal bars spaced 1-13 mm apart on a computer-controlled OPTACON stimulator placed over glabrous skin. Two-point resolution was measured by simultaneously pulsing pairs of rows at rates of 100, 50 and 25 Hz; each pair was shifted in tandem across the hand to simulate lateral motion. Single-fiber recordings were made from physiologically identified RA afferents in anesthetized monkeys. 3. Receptive field diameter appears to be the critical determinant of spatial resolution of gaps between two bars. RAs fire continuously if bar spacing is less than the field diameter but do not summate inputs when both active rows are contained within the field. Response profiles evoked by two bars spaced less than 4.8 mm apart can be predicted from the single-bar profiles, assuming occlusion between overlapping inputs with the strongest member dominating axonal output. Two-thirds of the RAs tested discharge 1 spike/pulse as bar patterns cross the field, yielding a uniform spike train whose frequency reflects stimulus pulse rates but fails to indicate gaps between bars. An additional 17% fire 2 spikes/pulse when the bars contact or straddle the field center, but also fail to differentiate individual stripes spaced less than 3.6 mm apart. 4. Only 17% of RAs represent gaps narrower than the field diameter. These fibers show double-peaked response profiles to bar patterns spaced at least 2.4 mm apart, firing 2 spikes/pulse as first one, and then the second stripe crosses the field center. Timing between peaks corresponds to bar spacing. Responses are reduced in amplitude when adjacent bars straddle the field center, as occlusion between simultaneous inputs prevents summation of inputs from the two stimuli. Fifteen of 16 RAs failed to resolve bars spaced 1.2 mm apart, as double-spike responses were evoked only by the leading stripe.(ABSTRACT TRUNCATED AT 400 WORDS)