Porro Carlo A, Martinig Michela, Facchin Patrizia, Maieron Marta, Jones Anthony K P, Fadiga Luciano
Department of Biomedical Sciences, Section of Human Physiology, University of Modena and Reggio Emilia, Via Campi 287, 41100 Modena, Italy.
Behav Brain Res. 2007 Mar 28;178(2):183-9. doi: 10.1016/j.bbr.2006.11.011. Epub 2007 Jan 17.
The cortical system underlying perceptual ability to localize tactile and noxious cutaneous stimuli in humans is still incompletely understood. We used transcranial magnetic stimulation (TMS) to transiently interfere with the function of the parietal cortex, at different times after the beginning of noxious or non-noxious mechanical stimulation of the hairy skin overlying the dorsal surface of the first metacarpal of the contralateral hand. Peripheral stimuli consisted of rounded (1mm diameter) or sharp (0.2 mm) metal tips; skin contact lasted on average 242 ms (noxious) and 228 ms (non-noxious). Brief (80 ms, 25 Hz) TMS trains, given at 150 ms after the onset of cutaneous stimulation, significantly impaired subjects' ability in localizing non-nociceptive, tactile input, an effect which was not observed when TMS was applied at 300 ms after cutaneous stimulation. In contrast, brief TMS trains given at 300 ms after the onset of cutaneous stimulation significantly impaired subjects' ability in localizing nociceptive input, an effect which was not observed when TMS was applied at 150 ms after cutaneous stimulation. No impairment in stimulus detection was found in comparison with control sham TMS. The timing of parietal TMS interference with the ability to localize tactile and painful stimuli is compatible with known time differences in the arrival of non-noxious and noxious information in the postcentral gyrus. On these grounds, our findings support the existence of overlapping cortical populations in the contralateral parietal lobe, exerting a role in spatial discriminative aspects of touch and mechanically induced pain.
人类中负责定位触觉和有害皮肤刺激的感知能力的皮质系统仍未被完全理解。我们使用经颅磁刺激（TMS）在对侧手第一掌骨背侧覆盖的多毛皮肤开始进行有害或无害机械刺激后的不同时间，短暂干扰顶叶皮质的功能。外周刺激由圆形（直径1毫米）或尖锐（0.2毫米）的金属尖端组成；皮肤接触平均持续242毫秒（有害）和228毫秒（无害）。在皮肤刺激开始后150毫秒给予短暂（80毫秒，25赫兹）的TMS脉冲串，显著损害了受试者定位非伤害性触觉输入的能力，而在皮肤刺激后300毫秒施加TMS时未观察到这种效应。相反，在皮肤刺激开始后300毫秒给予短暂的TMS脉冲串显著损害了受试者定位伤害性输入的能力，而在皮肤刺激后150毫秒施加TMS时未观察到这种效应。与对照假TMS相比，未发现刺激检测受损。顶叶TMS干扰触觉和疼痛刺激定位能力的时间与已知的非伤害性和伤害性信息到达中央后回的时间差异相符。基于这些理由，我们的研究结果支持对侧顶叶存在重叠的皮质群体，它们在触觉和机械性疼痛的空间辨别方面发挥作用。
