Vizzari V, Barba S, Gindri P, Duca S, Giobbe D, Cerrato P, Geminiani G, Torta D M
Department of Psychology, Universita' degli studi di Torino, Italy.
San Camillo Hospital, Torino, Italy.
Eur J Pain. 2017 Apr;21(4):738-749. doi: 10.1002/ejp.978. Epub 2016 Dec 15.
Crossing the hands over the midline can reduce the perceived intensity of nociceptive stimuli applied onto the hands. It remains unclear to what extent intact representation of peripersonal space influences this effect. Here we used the crossed-hands paradigm in patients with unilateral spatial neglect, a neuropsychological condition characterized by the inability to detect, attend and respond to contralesional (most often left) stimuli, and spared ability to process stimuli in the non-affected space.
Sixteen post-stroke patients without unilateral neglect and 11 patients with unilateral spatial neglect received punctate mechanical pinprick stimuli onto their crossed or uncrossed hands. We tested: (i) whether deficits in space representation reduce the possibility of observing 'crossed-hands analgesia', and; (ii) whether placing the contralesional hand, normally lying in the affected space in the healthy space would increase the number of detected stimuli.
Our results showed that neglect patients did not exhibit 'crossed-hands' analgesia, but did not provide strong evidence for an improvement in the number of detected stimuli when the contralesional hand was in the healthy space.
These findings uphold the notion that the perception of nociceptive stimuli is modulated by the relative position of the hands in space, but raise questions about the conditions under which these effects may arise.
We show that deficits in space representation can influence the processing of mechanical pinprick stimuli. Our results raise several questions on the mechanisms underlying these effects, which are relevant for the clinical practice.
双手交叉于身体中线之上可降低施加在手部的伤害性刺激的感知强度。目前尚不清楚个人周边空间的完整表征在多大程度上影响这一效应。在此，我们在单侧空间忽视患者中采用了双手交叉范式，单侧空间忽视是一种神经心理状况，其特征为无法检测、关注和应对对侧（最常见为左侧）刺激，而在未受影响空间中处理刺激的能力则得以保留。
16名无单侧忽视的中风后患者和11名单侧空间忽视患者在其交叉或未交叉的手上接受点状机械针刺刺激。我们测试了：（i）空间表征缺陷是否会降低观察到“双手交叉镇痛”的可能性，以及；（ii）将通常位于患侧空间的对侧手放置在健康空间中是否会增加检测到的刺激数量。
我们的结果表明，忽视患者未表现出“双手交叉”镇痛，但在对侧手位于健康空间时，也没有提供有力证据表明检测到的刺激数量有所增加。
这些发现支持了伤害性刺激的感知受双手在空间中相对位置调节的观点，但也引发了关于这些效应可能出现的条件的问题。
我们表明空间表征缺陷可影响机械针刺刺激的处理。我们的结果对这些效应背后的机制提出了几个问题，这些问题与临床实践相关。
