Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, 37134, Verona, Italy.
Center for Mind/Brain Sciences, University of Trento, Via delle Regole, 101, 38122, Trento, Italy.
Sci Rep. 2020 Sep 25;10(1):15774. doi: 10.1038/s41598-020-72554-x.
Haptic exploration produces mental object representations that can be memorized for subsequent object-directed behaviour. Storage of haptically-acquired object images (HOIs), engages, besides canonical somatosensory areas, the early visual cortex (EVC). Clear evidence for a causal contribution of EVC to HOI representation is still lacking. The use of visual information by the grasping system undergoes necessarily a frame of reference shift by integrating eye-position. We hypothesize that if the motor system uses HOIs stored in a retinotopic coding in the visual cortex, then its use is likely to depend at least in part on eye position. We measured the kinematics of 4 fingers in the right hand of 15 healthy participants during the task of grasping different unseen objects behind an opaque panel, that had been previously explored haptically. The participants never saw the object and operated exclusively based on haptic information. The position of the object was fixed, in front of the participant, but the subject's gaze varied from trial to trial between 3 possible positions, towards the unseen object or away from it, on either side. Results showed that the middle and little fingers' kinematics during reaching for the unseen object changed significantly according to gaze position. In a control experiment we showed that intransitive hand movements were not modulated by gaze direction. Manipulating eye-position produces small but significant configuration errors, (behavioural errors due to shifts in frame of reference) possibly related to an eye-centered frame of reference, despite the absence of visual information, indicating sharing of resources between the haptic and the visual/oculomotor system to delayed haptic grasping.
触觉探索产生的心理物体表象可以被记住，以便随后进行物体定向行为。存储触觉获取的物体图像（HOI）不仅涉及到经典的体感区域，还涉及到早期视觉皮层（EVC）。EVC 对 HOI 表示的因果贡献的明确证据仍然缺乏。抓取系统对视觉信息的使用必然需要通过整合眼位进行参考系转换。我们假设，如果运动系统使用存储在视觉皮层中的基于视网膜的 HOI 编码，那么其使用可能至少部分依赖于眼位。我们测量了 15 名健康参与者右手的 4 个手指的运动学，在该任务中，参与者在一个不透明的面板后面抓取不同的看不见的物体，这些物体之前已经被触觉探索过。参与者从未见过物体，仅根据触觉信息进行操作。物体的位置固定在参与者的前面，但参与者的注视位置从一次试验到另一次试验在 3 个可能的位置之间变化，朝向看不见的物体或远离它，在两侧。结果表明，在伸手去抓看不见的物体时，中间指和小指的运动学根据注视位置发生了显著变化。在一个对照实验中，我们表明非传递性手部运动不受注视方向的调节。尽管没有视觉信息，但操纵眼位会产生微小但显著的配置错误（由于参考系变化引起的行为错误），这可能与以眼睛为中心的参考系有关，表明触觉和视觉/眼动系统之间存在资源共享，以进行延迟的触觉抓取。
