Neuroscience Research Australia, University of New South Wales, Randwick, New South Wales, Australia.
School of Medical Sciences, University of New South Wales Randwick , New South Wales , Australia.
J Neurophysiol. 2019 Mar 1;121(3):764-772. doi: 10.1152/jn.00189.2018. Epub 2019 Jan 9.
Weak electrocutaneous stimuli applied to the forearm are erroneously localized toward its middle (Steenbergen P, Buitenweg JR, Trojan J, Veltink PH. Exp Brain Res 232: 597-607, 2014). We asked whether mechanical touch stimuli exhibit a similar bias and whether the bias is toward the middle of the forearm or toward the middle of the recent stimulus distribution. In experiments 1 and 2, participants ( n = 12 and n = 10) localized by pointing von Frey filaments applied to four locations on the dorsal forearm. Individually adjusted weak and strong stimuli ( experiment 1) or two levels of strong stimuli ( experiment 2) were presented in single sessions in random order. Weaker stimuli were localized with greater variability than the strong, with compression toward the middle of the forearm. Responses to the two levels of strong stimuli did not differ. In experiment 3, participants ( n = 16) were presented two spatially offset stimulus distributions (8 cm center-to-center), each offset from the forearm middle, on 2 different days. Out of four target locations comprising each distribution, two were shared. Responses to weak stimuli were compressed compared with responses to strong stimuli. Importantly, biases for the common targets had opposite directions, each being toward the middle of the distribution within which targets were presented. Responses to strong stimuli also exhibited a distribution-dependent bias, a 2-cm overall shift across the forearm midpoint. We conclude that touch localization is subject to intensity-dependent biases determined by the recent history of stimulation and possibly also by the available or perceived response space. NEW & NOTEWORTHY Recent findings show that weak electrical stimuli applied to the forearm are mislocalized toward the forearm middle, relative to strong stimuli. We found that weak mechanical stimuli are similarly mislocalized. The bias changed if, as a group, stimuli were not centered on the forearm middle: weak stimuli gravitated toward the center of prior stimulation. Localization of strong stimuli was also biased, consistent with the tendency to center responses within the available response space.
前臂受到的弱电刺激会被错误地定位到其中部（Steenbergen P、Buitenweg JR、Trojan J 和 Veltink PH，Exp Brain Res 232: 597-607, 2014）。我们想知道机械触觉刺激是否也存在类似的偏差，以及这种偏差是朝向前臂中部还是朝向最近的刺激分布的中部。在实验 1 和 2 中，参与者（n=12 和 n=10）通过指向施加在前臂背侧四个位置的冯·弗雷（von Frey）纤维来定位。在单独的会话中，以随机顺序呈现个体调整的弱和强刺激（实验 1）或两种强度的强刺激（实验 2）。较弱的刺激定位的变异性大于强刺激，向前臂中部压缩。两种强度的强刺激的反应没有差异。在实验 3 中，参与者（n=16）在 2 天内接受了两个空间偏移的刺激分布（中心到中心 8 厘米），每个分布都偏离前臂中部。每个分布由四个目标位置组成，其中两个是共享的。与强刺激相比，弱刺激的反应被压缩。重要的是，共同目标的偏差方向相反，每个目标都朝向所呈现的分布的中部。强刺激的反应也表现出与分布相关的偏差，在前臂中点处整体移动 2 厘米。我们的结论是，触觉定位受到刺激的历史和可能还有可用或感知的反应空间决定的强度相关偏差的影响。新的和值得注意的是，最近的发现表明，相对于强刺激，施加在前臂上的弱电流刺激会错误地定位到手前臂中部。我们发现弱机械刺激也存在类似的错误定位。如果刺激不是集中在前臂中部，作为一个整体，刺激的偏差会发生变化：弱刺激会向先前刺激的中心移动。强刺激的定位也存在偏差，这与集中反应在可用反应空间内的趋势一致。
