Department of Neurology, University of Erlangen-Nuremberg, Erlangen, Germany.
Eur J Pain. 2014 Jan;18(1):56-66. doi: 10.1002/j.1532-2149.2013.00339.x. Epub 2013 May 29.
Habituation to repetitive noxious stimuli is a well-known phenomenon. We investigated brain correlates of habituation to pain in a transdermal electrical pain model using functional magnetic resonance imaging (fMRI).
Electrical painful stimulation with 1 Hz was applied to the volar forearm of 48 healthy subjects for 45 min. Before and after conditioning stimulation, psychophysical testing and fMRI were performed. During fMRI sessions, the subjects underwent blockwise painful electrical stimulation with a fixed percept-adapted current intensity. After fMRI 1 and fMRI 2 subjects rated the individual pain intensity of the electrical stimulus.
Substantial habituation occurred during conditioning electrical stimulation. Accordingly, areas typically involved in pain processing showed decreased activity after conditioning stimulation. The blood oxygen level-dependent signal of the subgenual anterior cingulate gyrus, the superior parietal lobule and the supplemental motor area correlated positively with habituation. In contrast, activity in the periaqueductal grey, thalamus and insula correlated negatively. The results of the correlation analyses did not survive correction for multiple comparisons.
With this study, we identified central components associated with habituation to repetitive painful stimuli. The results suggest that an increase in tonic inhibitory activity in cortical pain processing areas is a major mechanism contributing to habituation to phasic noxious stimuli. Moreover, areas involved in descending pain modulation were differentially modulated. This may hint at a simultaneous activation of facilitating and inhibiting nociceptive systems that are both altered in the transdermal electrical pain model.
对重复有害刺激的习惯化是一种众所周知的现象。我们使用功能磁共振成像（fMRI）研究了经皮电疼痛模型中对疼痛习惯化的大脑相关性。
使用 1 Hz 的电刺激对 48 名健康受试者的掌侧前臂进行 45 分钟的刺激。在条件刺激之前和之后进行心理物理测试和 fMRI。在 fMRI 期间，受试者接受了带有固定感知适应电流强度的块状电疼痛刺激。在 fMRI1 和 fMRI2 之后，受试者对电刺激的个体疼痛强度进行了评分。
在条件电刺激期间发生了明显的习惯化。因此，通常参与疼痛处理的区域在条件刺激后显示出活动减少。扣带回前下皮质、顶叶上回和辅助运动区的血氧水平依赖信号与习惯化呈正相关。相比之下，脑桥被盖部、丘脑和岛叶的活动与习惯化呈负相关。相关分析的结果在进行多重比较校正后没有保留。
通过这项研究，我们确定了与重复疼痛刺激习惯化相关的中枢成分。结果表明，皮质疼痛处理区域中紧张性抑制活动的增加是对相疼痛刺激习惯化的主要机制。此外，参与下行疼痛调节的区域也受到不同的调节。这可能暗示着促进和抑制伤害性系统的同时激活，这在经皮电疼痛模型中都发生了改变。
