NTT Communication Science Laboratories, Nippon Telegraph and Telephone Corporation, Atsugi, Japan.
Institute of Cognitive Neuroscience, University College London, London, United Kingdom.
J Neurophysiol. 2024 Dec 1;132(6):1805-1819. doi: 10.1152/jn.00105.2024. Epub 2024 Oct 23.
When we run our hand across a surface, each finger typically repeats the sensory stimulation that the leading finger has already experienced. Because of this redundancy, the leading finger may attract more attention and contribute more strongly when tactile signals are integrated across fingers to form an overall percept. To test this hypothesis, we re-analyzed data collected in a previous study (Arslanova I, Takamuku S, Gomi H, Haggard P, 128: 418-433, 2022), where two probes were moved in different directions on two different fingerpads and participants reported the probes' average direction. Here, we evaluate the relative contribution of each finger to the percept and examine whether multidigit integration gives priority to the leading finger. Although the hand actually remained static in these experiments, a "functional leading finger" could be defined with reference to the average direction of the stimuli and the direction of hand-object relative motion that this implied. When participants averaged the motion direction across fingers of the same hand, the leading finger received a higher weighting than the nonleading finger, even though this biased estimate of average direction. Importantly, this bias disappeared when averaging motion direction across the two hands. Both the reported average direction and its systematic relation to the difference between the individual stimulus directions were explained by a model of motion integration in which the sensory weighting of stimuli depends on the directions of the applied stimuli. Our finding supports the hypothesis that the leading finger, which often receives novel information in natural hand-object interactions, is prioritized in forming our tactile perception. The capacity of the tactile system to process multiple simultaneous stimuli is restricted. One solution could be to prioritize input from more informative sources. Here, we show that sensory weighting accorded to each finger during multidigit touch is biased in a direction-dependent manner when different motions are delivered to the fingers of the same hand. We argue that tactile inputs are weighted based on purely geometric information to prioritize "novel" information from the leading finger.
当我们用手触摸一个表面时，每个手指通常会重复领先手指已经经历过的感觉刺激。由于这种冗余，当触觉信号在手指之间整合以形成整体感知时，领先手指可能会吸引更多的注意力并做出更强烈的贡献。为了验证这一假设，我们重新分析了之前一项研究（Arslanova I, Takamuku S, Gomi H, Haggard P, 128: 418-433, 2022）中收集的数据，在该研究中，两个探针在两个不同的指垫上以不同的方向移动，参与者报告探针的平均方向。在这里，我们评估每个手指对感知的相对贡献，并检查多数字整合是否优先考虑领先手指。虽然在这些实验中手实际上保持静止，但可以参考刺激的平均方向和手-物体相对运动的方向来定义“功能领先手指”。当参与者在同一只手的手指之间平均运动方向时，领先手指比非领先手指受到更高的权重，即使这种对平均方向的有偏差的估计。重要的是，当平均运动方向跨双手时，这种偏差就消失了。报告的平均方向及其与个体刺激方向差异的系统关系都可以用运动整合模型来解释，在该模型中，刺激的感觉权重取决于施加刺激的方向。我们的发现支持了这样一种假设，即领先手指在自然的手-物体交互中经常接收新信息，因此在形成我们的触觉感知中被优先考虑。触觉系统处理多个同时刺激的能力是有限的。一种解决方案可能是优先处理来自信息量更大的来源的输入。在这里，我们表明，当向同一只手的手指施加不同的运动时，多数字触摸过程中每个手指的感觉权重会以方向依赖的方式产生偏差。我们认为，触觉输入是根据纯粹的几何信息加权的，以优先考虑来自领先手指的“新”信息。
