Fossataro C, Bruno V, Bosso E, Chiotti V, Gindri P, Farnè A, Garbarini F
MANIBUS Lab, Psychology Department, University of Turin, Turin, Italy.
Centro Puzzle, Turin, Italy.
Cortex. 2020 Jun;127:94-107. doi: 10.1016/j.cortex.2020.02.004. Epub 2020 Feb 19.
When body ownership is impaired after brain-damage, the capacity to discriminate between one's own and others' body-parts is lost. Delusional body-ownership has been recently described in patients who misidentify someone else's limb as their own (pathological embodiment) whenever it is positioned in a body congruent position. This delusion can be frequently associated with somatosensory and attentional deficits. Here, we leveraged the phenomenon of tactile extinction, as this clinical sign can be substantially ameliorated when contralesional touches are combined with proximal visual stimulation. Is body ownership a necessary prerequisite to modulate cross-modal processing and thus reducing tactile extinction? Fourteen patients with tactile extinction (TE+) took part in the study: eight of them with pathological embodiment (E+, experimental group) and six of them without pathological embodiment (E-, control group). In two different paradigms, differing for the nature of visuo-tactile stimuli, bilateral tactile stimulation of the patients' hands was combined with visual stimuli occurring on A) their own contralesional (affected) hand, B) the examiner's hand (embodied in E+), or C) a neutral object. In both groups, visual stimuli proximal to the own hand significantly improved contralesional tactile detection, while visual stimuli occurring on the neutral object did not. Crucially, only in E+TE+ patients did visual stimuli on the examiner's (embodied) hand improve contralesional tactile detection. This finding shows that cross-modal visuo-tactile integration is conditional to body-ownership, so that it ameliorates tactile extinction when visual stimuli occur on what is believed to be one's own body. From a clinical point of view, this study suggests that the effectiveness of cross-modal rehabilitative intervention can benefit from a careful evaluation of the patients' sense of body-ownership, so often impaired after brain-damage.
当脑损伤后身体自我认知受损时，区分自己和他人身体部位的能力就会丧失。最近，在一些患者中发现了妄想性身体自我认知，这些患者在他人肢体处于身体一致位置时，会将别人的肢体误认成自己的（病理性体现）。这种妄想常常与躯体感觉和注意力缺陷有关。在此，我们利用了触觉消退现象，因为当对侧触觉与近端视觉刺激相结合时，这一临床症状可得到显著改善。身体自我认知是调节跨模态加工从而减少触觉消退的必要前提吗？14名有触觉消退的患者（TE+）参与了这项研究：其中8名有病理体现（E+，实验组），6名没有病理体现（E-，对照组）。在两种不同的范式中，根据视觉触觉刺激的性质不同，对患者双手进行双侧触觉刺激，并与以下视觉刺激相结合：A）他们自己对侧（受影响）的手，B）检查者的手（在E+中有体现），或C）一个中性物体。在两组中，靠近自己手的视觉刺激显著改善了对侧触觉检测，而在中性物体上出现的视觉刺激则没有。至关重要的是，只有在E+TE+患者中，检查者（有体现）手上的视觉刺激才改善了对侧触觉检测。这一发现表明，跨模态视觉触觉整合以身体自我认知为条件，因此当视觉刺激出现在被认为是自己身体的部位时，它会改善触觉消退。从临床角度来看，这项研究表明，跨模态康复干预的有效性可以受益于对患者身体自我认知感的仔细评估，而这种认知感在脑损伤后常常受损。
