Percept Mot Skills. 2014 Apr;118(2):491-506. doi: 10.2466/24.27.PMS.118k18w5.
Although the behavioral characteristics and the neural correlates of prism adaptation processes have been studied extensively, the underlying mechanism is yet to be investigated. Recently, somatosensory suppression was heralded as a mechanism for the sensory re-alignment process accompanying the adaptation. Somatosensory suppression should facilitate the re-alignment process in the proprioceptive system. The shift in the proprioceptive system takes place mostly during a concurrent visual feedback (CVF) condition; during a terminal visual feedback (TVF) condition, the visual system experiences significant adaptation (visual shift), so somatosensory suppression should have minimal functional consequences under TVF. To test this hypothesis, a repetitive transcranial magnetic stimulation (rTMS) was applied to the primary somatosensory cortex as an artificial somatosensory suppression right after the reaching initiation in CVF and TVF conditions, and changes in adaptation were observed. Because somatosensory suppression is already in effect during CVF, rTMS would cause no significant changes. During TVF with rTMS, however, significantly different patterns of adaptation could be expected when compared to a sham rTMS condition. Young adults (N = 12) participated in 4 sessions (CVF/ TVF, real/sham rTMS); visual proprioceptive, and total shifts were measured. Movement time and curvature of the reaching movement were measured during the adaptation phase. Results showed that while the total shift was unchanged, the proprioceptive shift increased and the visual shift decreased in the TVF condition when rTMS was delivered. However, the total, proprioceptive, and visual shifts were not influenced by rTMS in the CVF condition. Suppression of proprioception induced by the rTMS could be one of the requisites for successful proprioceptive shift during prism adaptation.
尽管已经广泛研究了棱镜适应过程的行为特征和神经相关性，但潜在的机制仍有待研究。最近，躯体感觉抑制被认为是伴随适应的感觉重新校准过程的一种机制。躯体感觉抑制应该有利于本体感觉系统的重新校准过程。本体感觉的转变主要发生在同时进行的视觉反馈（CVF）条件下；在终端视觉反馈（TVF）条件下，视觉系统经历了显著的适应（视觉转变），因此在 TVF 条件下，躯体感觉抑制应该只有最小的功能后果。为了验证这一假设，在 CVF 和 TVF 条件下，在起始伸手后立即对初级躯体感觉皮层施加重复经颅磁刺激（rTMS）作为人工躯体感觉抑制，并观察适应的变化。因为在 CVF 中已经存在躯体感觉抑制，所以 rTMS 不会引起显著变化。然而，在 TVF 中，与假 rTMS 条件相比，可能会预期到适应的模式有明显的不同。年轻成年人（N=12）参加了 4 个会话（CVF/TVF，真实/rTMS 假）；测量了视觉本体感觉和总偏移。在适应阶段测量了运动时间和伸手运动的曲率。结果表明，虽然总偏移保持不变，但在 rTMS 施加时，TVF 条件下本体感觉偏移增加，视觉偏移减少。然而，在 CVF 条件下，rTMS 对总、本体感觉和视觉偏移没有影响。rTMS 引起的本体感觉抑制可能是棱镜适应过程中成功进行本体感觉转移的必要条件之一。
