Moulton E A, Keaser M L, Gullapalli R P, Greenspan J D
Program in Neuroscience, University of Maryland, Baltimore, MD 21201, USA.
J Neurophysiol. 2005 Apr;93(4):2183-93. doi: 10.1152/jn.01025.2004. Epub 2004 Dec 15.
Cortical responses to painful and nonpainful heat were measured using functional magnetic resonance imaging (fMRI) region of interest analysis (ROI) of primary somatosensory cortex (S1), secondary somatosensory cortex (S2), anterior cingulate (ACC), supplementary motor area (SMA), insula, and inferior frontal gyrus (IFG). Previous studies indicated that innocuous and noxious stimuli of different modalities produce responses with different time courses in S1 and S2. The aim of this study was to 1) determine whether temporally distinct nociceptive blood oxygen level-dependent (BOLD) responses are evoked in multiple somatosensory processing cortical areas and 2) whether these responses discriminate small noxious stimulus intensity differences. Thirty-three subjects underwent fMRI scanning while receiving three intensities of thermal stimuli, ranging from innocuous warm (41 degrees C) to 1 degrees C below tolerance, applied to the dorsum of the left foot. Innocuous and noxious responses were distinguishable in contralateral S1, the mid-ACC, and SMA. The peak of the nociceptive response was temporally delayed from the innocuous response peak by 6-8 s. Responses to noxious but not to innocuous stimuli were observed in contralateral posterior insula. Responses to innocuous and noxious stimuli were not statistically different in contralateral S2. In contralateral S1 only, the nociceptive response could differentiate heat stimuli separated by 1 degrees C. These results show that 1) multiple cortical areas have temporally distinguishable innocuous and noxious responses evoked by a painfully hot thermode, 2) the nociceptive processing properties vary across cortical regions, and 3) nociceptive responses in S1 discriminate between painful temperatures at a level unmatched in other cortical areas.
使用功能磁共振成像（fMRI）对初级体感皮层（S1）、次级体感皮层（S2）、前扣带回（ACC）、辅助运动区（SMA）、脑岛和额下回（IFG）进行感兴趣区域分析（ROI），测量皮层对疼痛和非疼痛热刺激的反应。先前的研究表明，不同模态的无害和有害刺激在S1和S2中产生具有不同时间进程的反应。本研究的目的是：1）确定在多个体感处理皮层区域是否诱发了时间上不同的伤害性血氧水平依赖（BOLD）反应；2）这些反应是否能区分小的有害刺激强度差异。33名受试者在接受三种强度的热刺激（从无害的温暖刺激（41摄氏度）到低于耐受温度1摄氏度）时进行fMRI扫描，刺激施加于左脚背。在对侧S1、ACC中部和SMA中，无害和有害反应是可区分的。伤害性反应的峰值在时间上比无害反应峰值延迟6 - 8秒。在对侧后岛叶观察到对有害刺激而非无害刺激的反应。在对侧S2中，对无害和有害刺激的反应在统计学上没有差异。仅在对侧S1中，伤害性反应能够区分相差1摄氏度的热刺激。这些结果表明：1）多个皮层区域对热刺激模式产生了时间上可区分的无害和有害反应；2）伤害性处理特性在不同皮层区域有所不同；3）S1中的伤害性反应在区分疼痛温度方面的水平是其他皮层区域无法比拟的。
