Folger Stephen E, Tannan Vinay, Zhang Zheng, Holden Jameson K, Tommerdahl Mark
Department of Physical Therapy Education, Elon University, Elon, NC 27244, USA.
BMC Neurosci. 2008 Sep 16;9:87. doi: 10.1186/1471-2202-9-87.
Previous reports have demonstrated that short durations of vibrotactile stimuli (less than or equal to 2 sec) effectively and consistently modify both the perceptual response in humans as well as the neurophysiological response in somatosensory cortex. The change in cortical response with adaptation has been well established by a number of studies, and other reports have extended those findings in determining that both GABA- and NMDAR-mediated neurotransmission play a significant role in the dynamic response of somatosensory cortical neurons. In this study, we evaluated the impact that dextromethorphan (DXM), an NMDAR antagonist, had on two distinct vibrotactile adaptation tasks.
All subjects, both those that ingested 60 mg DXM and those that ingested placebo, were evaluated for their amplitude discriminative capacity between two simultaneously delivered vibrotactile stimuli both with and without 3 conditions of pre-exposure to adapting stimulation. The results demonstrated that the perceptual metrics of subjects who ingested 60 mg DXM were significantly altered from that of controls when the amplitude discrimination task followed one of the conditions of adapting stimulation. Without the condition of pre-exposure to an adapting stimulus (or stimuli), there was little difference between the observations obtained from the subjects that ingested DXM and controls. Peak impact on subject response occurred at 60 min post-ingestion, whereas the scores of controls who ingested placebo were not impacted.
The results - that DXM blocks vibrotactile adaptation - is consistent with the suggestion that NMDAR-mediated neurotransmission plays a significant role in the perceptual adaptive response. This finding is also consistent with neurophysiological findings that report observations of the effects of NMDAR block on the SI cortical response to repetitive vibrotactile stimulation.
先前的报告表明，短时间的振动触觉刺激（小于或等于2秒）能有效且持续地改变人类的感知反应以及体感皮层的神经生理反应。许多研究已经充分证实了随着适应过程皮层反应的变化，其他报告进一步扩展了这些发现，确定γ-氨基丁酸（GABA）和N-甲基-D-天冬氨酸受体（NMDAR）介导的神经传递在体感皮层神经元的动态反应中都起着重要作用。在本研究中，我们评估了NMDAR拮抗剂右美沙芬（DXM）对两种不同的振动触觉适应任务的影响。
所有受试者，包括摄入60毫克DXM的受试者和摄入安慰剂的受试者，都在有和没有3种预暴露于适应性刺激条件下，接受了对同时施加的两种振动触觉刺激之间的幅度辨别能力评估。结果表明，当幅度辨别任务遵循其中一种适应性刺激条件时，摄入60毫克DXM的受试者的感知指标与对照组相比有显著改变。在没有预暴露于适应性刺激的条件下，摄入DXM的受试者和对照组的观察结果几乎没有差异。对受试者反应的峰值影响出现在摄入后60分钟，而摄入安慰剂的对照组的分数没有受到影响。
DXM阻断振动触觉适应这一结果与NMDAR介导的神经传递在感知适应性反应中起重要作用的观点一致。这一发现也与神经生理学研究结果一致，该研究报告了NMDAR阻断对体感皮层对重复性振动触觉刺激反应的影响。
