Department of Health Science and Technology, Aalborg University, Selma Lagerløfs Vej 249, 9260, Gistrup, Denmark.
Tecnalia Serbia Ltd, Deligradska 9/39, 11000, Belgrade, Serbia.
Exp Brain Res. 2024 May;242(5):1047-1060. doi: 10.1007/s00221-024-06794-y. Epub 2024 Mar 12.
Electrotactile stimulation through matrix electrodes is a promising technology to restore high-resolution tactile feedback in extended reality applications. One of the fundamental tactile effects that should be simulated is the change in the size of the contact between the finger and a virtual object. The present study investigated how participants perceive the increase of stimulation area when stimulating the index finger using static or dynamic (moving) stimuli produced by activating 1 to 6 electrode pads. To assess the ability to interpret the stimulation from the natural cues (natural decoding), without any prior training, the participants were instructed to draw the size of the stimulated area and identify the size difference when comparing two consecutive stimulations. To investigate if other "non-natural" cues can improve the size estimation, the participants were asked to enumerate the number of active pads following a training protocol. The results demonstrated that participants could perceive the change in size without prior training (e.g., the estimated area correlated with the stimulated area, p < 0.001; ≥ two-pad difference recognized with > 80% success rate). However, natural decoding was also challenging, as the response area changed gradually and sometimes in complex patterns when increasing the number of active pads (e.g., four extra pads needed for the statistically significant difference). Nevertheless, by training the participants to utilize additional cues the limitations of natural perception could be compensated. After the training, the mismatch in the activated and estimated number of pads was less than one pad regardless of the stimulus size. Finally, introducing the movement of the stimulus substantially improved discrimination (e.g., 100% median success rate to recognize ≥ one-pad difference). The present study, therefore, provides insights into stimulation size perception, and practical guidelines on how to modulate pad activation to change the perceived size in static and dynamic scenarios.
通过矩阵电极进行电触觉刺激是一种很有前途的技术，可以在扩展现实应用中恢复高分辨率触觉反馈。应该模拟的基本触觉效果之一是手指与虚拟物体之间接触面积的变化。本研究调查了在使用静态或动态（移动）刺激刺激食指时，参与者如何感知刺激区域的增加，这些刺激是通过激活 1 到 6 个电极垫产生的。为了评估在没有任何预先训练的情况下从自然线索（自然解码）解释刺激的能力，参与者被指示画出刺激区域的大小，并在比较两次连续刺激时识别大小差异。为了研究其他“非自然”线索是否可以改善尺寸估计，要求参与者按照训练协议数出激活的电极垫数量。结果表明，参与者可以在没有预先训练的情况下感知尺寸的变化（例如，估计区域与刺激区域相关，p < 0.001；识别两个连续刺激之间的差异成功率超过 80%）。然而，自然解码也具有挑战性，因为当增加电极垫的数量时，响应区域会逐渐变化，有时会呈现复杂的模式（例如，需要增加四个额外的电极垫才能产生具有统计学意义的差异）。尽管如此，通过训练参与者利用额外的线索，可以弥补自然感知的局限性。经过训练，激活和估计的电极垫数量之间的不匹配小于一个电极垫，无论刺激大小如何。最后，引入刺激的运动可以显著提高辨别力（例如，识别差异大于一个电极垫的成功率达到 100%）。因此，本研究提供了关于刺激尺寸感知的见解，并提供了如何在静态和动态场景中调节电极垫激活以改变感知尺寸的实用指南。
