Fiorio Mirta, Marotta Angela, Ottaviani Sarah, Pozzer Lara, Tinazzi Michele
Department of Neurological and Movement Sciences, University of Verona, Verona, Italy.
Neurology Unit and Department of Neuroscience, Borgo Trento Civil Hospital, Verona, Italy.
PLoS One. 2014 Feb 11;9(2):e88686. doi: 10.1371/journal.pone.0088686. eCollection 2014.
Sensory alterations, a common feature of such movement disorders as Parkinson's disease (PD) and dystonia, could emerge as epiphenomena of basal ganglia dysfunction. Recently, we found a selective reduction of tactile perception (Aristotle's illusion, the illusory doubling sensation of one object when touched with crossed fingers) in the affected hand of patients with focal hand dystonia. This suggests that reduced tactile illusion might be a specific feature of this type of dystonia and could be due to abnormal somatosensory cortical activation. The aim of the current study was to investigate whether Aristotle's illusion is reduced in the affected hand of patients with PD. We tested 15 PD patients, in whom motor symptoms were mainly localised to one side of the body, and 15 healthy controls. Three pairs of fingers were tested in crossed (evoking the illusion) or parallel position (not evoking the illusion). A sphere was placed in the contact point between the two fingers and the blindfolded participants had to say whether they felt one or two stimuli. Stimuli were applied on the affected and less or unaffected side of the PD patients. We found no difference in illusory perception between the PD patients and the controls, nor between the more affected and less/unaffected side, suggesting that Aristotle's illusion is preserved in PD. The retained tactile illusion in PD and its reduction in focal hand dystonia suggest that the basal ganglia, which are dysfunctional in both PD and dystonia, may not be causally involved in this function. Instead, the level of activation between digits in the somatosensory cortex may be more directly involved. Finally, the similar percentage of illusion in the more affected and less or unaffected body sides indicates that the illusory perception is not influenced by the presence or amount of motor symptoms.
感觉改变是帕金森病（PD）和肌张力障碍等运动障碍的常见特征，可能是基底神经节功能障碍的附带现象。最近，我们发现局灶性手部肌张力障碍患者患侧手部的触觉感知（亚里士多德错觉，即交叉手指触摸一个物体时产生的物体双倍错觉）选择性降低。这表明触觉错觉降低可能是这种肌张力障碍的一个特定特征，可能是由于体感皮层激活异常所致。本研究的目的是调查PD患者患侧手部的亚里士多德错觉是否降低。我们测试了15名运动症状主要局限于身体一侧的PD患者和15名健康对照者。测试了三对手指处于交叉（诱发错觉）或平行位置（不诱发错觉）的情况。在两根手指的接触点放置一个球体，蒙眼的参与者必须说出他们感觉到的是一个还是两个刺激。刺激施加在PD患者的患侧以及较少受累或未受累侧。我们发现PD患者与对照组之间、患侧与较少受累/未受累侧之间在错觉感知上没有差异，这表明PD患者保留了亚里士多德错觉。PD患者保留的触觉错觉及其在局灶性手部肌张力障碍中的降低表明，在PD和肌张力障碍中均功能失调的基底神经节可能与该功能没有因果关系。相反，体感皮层中手指间的激活水平可能更直接相关。最后，患侧与较少受累或未受累身体侧的错觉百分比相似，表明错觉感知不受运动症状的存在或程度影响。
