NEXT: Neurophysiology and Neuroengineering of Human-Technology Interaction Research Unit, Università Campus Bio-Medico di Roma, Rome 00128, Italy.
Neurorobotics Lab, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom.
eNeuro. 2024 Jun 19;11(6). doi: 10.1523/ENEURO.0244-23.2024. Print 2024 Jun.
In measurement, a reference frame is needed to compare the measured object to something already known. This raises the neuroscientific question of which reference frame is used by humans when exploring the environment. Previous studies suggested that, in touch, the body employed as measuring tool also serves as reference frame. Indeed, an artificial modification of the perceived dimensions of the body changes the tactile perception of external object dimensions. However, it is unknown if such a change in tactile perception would occur when the body schema is modified through the illusion of owning a limb altered in size. Therefore, employing a virtual hand illusion paradigm with an elongated forearm of different lengths, we systematically tested the subjective perception of distance between two points [tactile distance perception (TDP) task] on the corresponding real forearm following the illusion. Thus, the TDP task is used as a proxy to gauge changes in the body schema. Embodiment of the virtual arm was found significantly greater after the synchronous visuotactile stimulation condition compared with the asynchronous one, and the forearm elongation significantly increased the TDP. However, we did not find any link between the visuotactile-induced ownership over the elongated arm and TDP variation, suggesting that vision plays the main role in the modification of the body schema. Additionally, significant effect of elongation found on TDP but not on proprioception suggests that these are affected differently by body schema modifications. These findings confirm the body schema malleability and its role as a reference frame in touch.
在测量中，需要参考框架来将被测物体与已知的东西进行比较。这就提出了一个神经科学问题，即人类在探索环境时使用哪个参考框架。先前的研究表明，在触觉中，用作测量工具的身体也充当参考框架。事实上，身体感知尺寸的人为改变会改变对外界物体尺寸的触觉感知。然而，当身体图式通过改变大小的幻觉来改变时，这种触觉感知的变化是否会发生还不得而知。因此，我们使用具有不同长度的延长前臂的虚拟手错觉范式，系统地测试了对应真实前臂上两点之间的距离的主观感知[触觉距离感知（TDP）任务]。因此，TDP 任务被用作衡量身体图式变化的替代指标。与异步刺激条件相比，同步视触刺激条件下虚拟手臂的体现明显更大，前臂伸长显著增加了 TDP。然而，我们没有发现视触觉引起的对伸长手臂的所有权与 TDP 变化之间的任何联系，这表明视觉在身体图式的修改中起着主要作用。此外，在 TDP 上发现了伸长的显著影响，但在本体感觉上没有发现，这表明它们受到身体图式修改的不同影响。这些发现证实了身体图式的可塑和它在触觉中的参考框架作用。
