Centre Interdisciplinaire de Recherche en Réadaptation et en Intégration Sociale Québec, QC, Canada ; Département de Réadaptation, Faculté de Médecine, Université Laval Québec, QC, Canada.
Front Hum Neurosci. 2013 Mar 14;7:77. doi: 10.3389/fnhum.2013.00077. eCollection 2013.
Patients with chronic pain often show disturbances in their body perception. Understanding the exact role played by pain is however complex, as confounding factors can contribute to the observed deficits in these clinical populations. To address this question, acute experimental pain was used to test the effect of lateralized pain on body perception in healthy subjects. Subjects were asked to indicate the position of their body midline (subjective body midline, SBM) by stopping a moving luminescent dot projected on a screen placed in front of them, in a completely dark environment. The effect of other non-painful sensorimotor manipulations was also tested to assess the potential unspecific attentional effects of stimulating one side of the body. SBM judgment was made in 17 volunteers under control and three experimental conditions: (1) painful (heat) stimulation; (2) non-painful vibrotactile stimulation; and (3) muscle contraction. The effects of the stimulated side and the type of trial (control vs. experimental condition), were tested separately for each condition with a 2 × 2 repeated measures ANOVA. The analyses revealed a significant interaction in both pain (p = 0.05) and vibration conditions (p = 0.04). Post hoc tests showed opposite effects of pain and vibration. Pain applied on the right arm deviated the SBM toward the right (stimulated) side (p = 0.03) while vibration applied on the left arm deviated the SBM toward the right (not stimulated) side (p = 0.01). These opposite patterns suggest that the shift in SBM is likely to be specifically linked to the stimulation modality. It is concluded that acute experimental pain can induce an SBM shift toward the stimulated side, which might be functionally beneficial to protect the painful area of the body. Interestingly, it appears to be easier to bias SBM toward the right side, regardless of the modality and of the stimulated side.
患有慢性疼痛的患者通常表现出身体感知障碍。然而，要理解疼痛所起的确切作用非常复杂，因为混杂因素可能会导致这些临床人群中观察到的缺陷。为了解决这个问题，我们使用急性实验性疼痛来测试健康受试者中偏侧疼痛对身体感知的影响。要求受试者在完全黑暗的环境中，通过停止投射在他们面前屏幕上的移动发光点来指示身体中线的位置（主观身体中线，SBM）。还测试了其他非疼痛感觉运动操作的影响，以评估刺激身体一侧的潜在非特异性注意力效应。在 17 名志愿者中，在对照和三种实验条件下进行 SBM 判断：（1）疼痛（热）刺激；（2）非疼痛振动刺激；和（3）肌肉收缩。用 2 × 2 重复测量方差分析分别测试刺激侧和试验类型（对照与实验条件）的影响。分析显示在疼痛和振动条件下均存在显著的交互作用（p = 0.05 和 p = 0.04）。事后检验显示疼痛和振动的作用相反。右上肢的疼痛使 SBM 偏向右侧（刺激侧）（p = 0.03），而左上肢的振动使 SBM 偏向右侧（非刺激侧）（p = 0.01）。这些相反的模式表明，SBM 的偏移很可能与刺激方式特异性相关。因此，我们得出结论，急性实验性疼痛可引起 SBM 向刺激侧的偏移，这可能在功能上有助于保护身体的疼痛区域。有趣的是，无论刺激方式和刺激侧如何，似乎更容易使 SBM 偏向右侧。
