Traxler Juliane, Madden Victoria J, Moseley G Lorimer, Vlaeyen Johan W S
Research Centre for Health Psychology, KU Leuven, Leuven, Belgium.
Experimental Health Psychology, Maastricht University, Maastricht, Netherlands.
PeerJ. 2019 Mar 8;7:e6486. doi: 10.7717/peerj.6486. eCollection 2019.
Classical conditioning has frequently been shown to be capable of evoking fear of pain and avoidance behavior in the context of chronic pain. However, whether pain itself can be conditioned has rarely been investigated and remains a matter of debate. Therefore, the present study investigated whether pain threshold ratings can be modified by the presence of conditioned non-nociceptive sensory stimuli in healthy participant.
In 51 healthy volunteers, pain threshold to electrocutaneous stimuli was determined prior to participation in a simultaneous conditioning paradigm. Participants underwent an acquisition phase in which one non-painful vibrotactile stimulus (CS) was repeatedly paired with a painful electrocutaneous stimulus, whereas a second vibrotactile stimulus of the same quality and intensity (CS) was paired with a non-painful electrocutaneous stimulus. Stimulation was provided on the lower back with close proximity between the conditioned stimulus and the unconditioned stimulus. In the test phase, electrocutaneous stimuli at the individually-set threshold intensity were simultaneously delivered together with either a CS or CS. Pain intensity ratings were obtained after each trial; expectancy ratings were obtained after each block. The primary outcome was the percentage of test stimuli that were rated as painful.
Test stimuli were more likely to be rated as painful when they were paired with the CS than when they were paired with the CS. This effect was not influenced by contingency awareness, nor by expectancies or mood states.
The findings support the notion that the judgement of an event being painful or non-painful can be influenced by classical conditioning and corroborate the possible role of associative learning in the development and maintenance of chronic pain.
经典条件反射常常被证明能够在慢性疼痛的背景下引发对疼痛的恐惧和回避行为。然而，疼痛本身是否能够被条件化很少被研究，并且仍然存在争议。因此，本研究调查了在健康参与者中，条件性非伤害性感觉刺激的存在是否能改变疼痛阈值评级。
在51名健康志愿者中，在参与同步条件反射范式之前测定对皮肤电刺激的疼痛阈值。参与者经历一个习得阶段，其中一个非疼痛性振动触觉刺激（条件刺激）与一个疼痛性皮肤电刺激反复配对，而另一个相同质量和强度的振动触觉刺激（条件刺激）与一个非疼痛性皮肤电刺激配对。在下背部进行刺激，条件刺激和非条件刺激之间距离很近。在测试阶段，以个体设定的阈值强度的皮肤电刺激与条件刺激或条件刺激同时给予。每次试验后获得疼痛强度评级；每个组块后获得预期评级。主要结果是被评为疼痛的测试刺激的百分比。
与条件刺激配对时，测试刺激比与条件刺激配对时更有可能被评为疼痛。这种效应不受意外觉知的影响，也不受预期或情绪状态的影响。
这些发现支持这样一种观点，即一个事件是疼痛还是非疼痛的判断可以受到经典条件反射的影响，并证实了联想学习在慢性疼痛的发展和维持中可能发挥的作用。
