Henderson Luke A, Di Pietro Flavia, Youssef Andrew M, Lee Sinjeong, Tam Shirley, Akhter R, Mills Emily P, Murray Greg M, Peck Chris C, Macey Paul M
Department of Anatomy and Histology, The University of Sydney, Sydney, NSW, Australia.
School of Pharmacy and Biomedical Sciences, Curtin University, Perth, WA, Australia.
Front Neurosci. 2020 Jan 31;14:6. doi: 10.3389/fnins.2020.00006. eCollection 2020.
Pain is a complex phenomenon that is highly modifiable by expectation. Whilst the intensity of incoming noxious information plays a key role in the intensity of perceived pain, this intensity can be profoundly shaped by an individual's expectations. Modern brain imaging investigations have begun to detail the brain regions responsible for placebo and nocebo related changes in pain, but less is known about the neural basis of stimulus-expectancy changes in pain processing. In this functional magnetic resonance imaging study, we administered two separate protocols of the same noxious thermal stimuli to 24 healthy subjects. However, different expectations were elicited by different explanations to subjects prior to each protocol. During one protocol, pain intensities were matched to expectation and in the other protocol they were not. Pain intensity was measured continuously via a manually operated computerized visual analogue scale. When individuals expected the stimulus intensity to remain constant, but in reality it was surreptitiously increased or decreased, pain intensity ratings were significantly lower than when expectation and pain intensities were matched. When the stimulus intensities did not match expectations, various areas in the brain such as the amygdala, anterior cingulate cortex (ACC), dorsolateral prefrontal cortex (dlPFC), and the midbrain periaqueductal gray matter (PAG) displayed significantly different patterns of activity compared to instances when stimulus intensity and pain expectations were matched. These results show that stimulus-expectancy manipulation of pain intensity alters activity in both higher brain and brainstem centers which are known to modulate pain under various conditions.
疼痛是一种复杂的现象，很容易受到预期的影响。虽然传入的有害信息的强度在感知疼痛的强度中起着关键作用，但这种强度会受到个体预期的深刻影响。现代脑成像研究已经开始详细阐述负责安慰剂和反安慰剂相关疼痛变化的脑区，但对于疼痛处理中刺激预期变化的神经基础了解较少。在这项功能磁共振成像研究中，我们对24名健康受试者实施了两种不同方案的相同有害热刺激。然而，在每个方案之前，通过对受试者的不同解释引发了不同的预期。在一个方案中，疼痛强度与预期相匹配，而在另一个方案中则不匹配。通过手动操作的计算机化视觉模拟量表连续测量疼痛强度。当个体预期刺激强度保持不变，但实际上偷偷增加或减少时，疼痛强度评分显著低于预期和疼痛强度相匹配时。当刺激强度与预期不匹配时，与刺激强度和疼痛预期相匹配的情况相比，大脑中的各个区域，如杏仁核、前扣带回皮质（ACC）、背外侧前额叶皮质（dlPFC）和中脑导水管周围灰质（PAG），表现出明显不同的活动模式。这些结果表明，对疼痛强度的刺激预期操纵会改变已知在各种条件下调节疼痛的高级脑区和脑干中枢的活动。
