The BioRobotics Institute, Scuola Superiore Sant'Anna, Pontedera, Italy.
PLoS One. 2012;7(11):e50756. doi: 10.1371/journal.pone.0050756. Epub 2012 Nov 30.
Tactile feedback plays a key role in the attribution of a limb to the self and in the motor control of grasping and manipulation. However, due to technological limits, current prosthetic hands do not provide amputees with cutaneous touch feedback. Recent findings showed that amputees can be tricked into experiencing an alien rubber hand as part of their own body, by applying synchronous touches to the stump which is out of view, and to the rubber hand in full view. It was suggested that similar effects could be achieved by using a prosthesis with touch sensors that provides synchronous cutaneous feedback through an array of tactile stimulators on the stump. Such a prosthesis holds the potential to be easily incorporated within one's body scheme, because it would reproduce the perceptual illusion in everyday usage. We propose to use sensory substitution--specifically vibrotactile--to address this issue, as current haptic technology is still too bulky and inefficient. In this basic study we addressed the fundamental question of whether visuo-tactile modality mismatch promotes self-attribution of a limb, and to what extent compared to a modality-matched paradigm, on normally-limbed subjects. We manipulated visuo-tactile stimulations, comprising combinations of modality matched, modality mismatched, synchronous and asynchronous stimulations, in a set of experiments fashioned after the Rubber Hand Illusion. Modality mismatched stimulation was provided using a keypad-controlled vibrotactile display. Results from three independent measures of embodiment (questionnaires, pointing tests and skin conductance responses) indicate that vibrotactile sensory substitution can be used to induce self-attribution of a rubber hand when synchronous but modality-conflicting visuo-tactile stimulation is delivered to the biological finger pads and to the equivalent rubber hand phalanges.
触觉反馈在将肢体归因于自身以及在抓握和操纵的运动控制中起着关键作用。然而，由于技术限制，目前的假肢手无法为截肢者提供皮肤触摸反馈。最近的研究结果表明，通过在截肢者无法看到的残肢上施加同步触摸，同时在完全可见的橡胶手上施加触摸，可以欺骗截肢者体验到一个外来的橡胶手作为自己身体的一部分。有人认为，通过使用带有触摸传感器的假肢，通过在残肢上排列的一系列触觉刺激器提供同步的皮肤反馈，可以达到类似的效果。这种假肢具有很容易融入身体计划的潜力，因为它将在日常使用中再现感知错觉。我们建议使用感觉替代——特别是振动触觉——来解决这个问题，因为目前的触觉技术仍然过于庞大和低效。在这项基础研究中，我们提出了一个基本问题，即视触觉模态不匹配是否会促进肢体的自我归因，以及与模态匹配范式相比，在正常肢体的受试者中会达到什么程度。我们在模仿橡胶手错觉的一系列实验中操纵了视触觉刺激，包括模态匹配、模态不匹配、同步和异步刺激的组合。模态不匹配刺激是通过一个由键盘控制的振动触觉显示器提供的。来自三个独立的体现测量（问卷调查、指向测试和皮肤电反应）的结果表明，当同步但视触觉模态冲突的刺激被传递到生物指垫和等效的橡胶手指骨时，振动触觉感觉替代可以用于诱导橡胶手的自我归因。
