对疼痛线索的晚期注视偏向预测慢性疼痛的维持:来自眼动的证据

The gaze biases towards pain-related information during the late stages predict the persistence of chronic pain:Evidence from eye movements

使用点探测视觉任务和融入真实疼痛刺激的视觉任务,以疼痛-中性、中性-中性图片为实验材料,采用眼动追踪技术,测量慢性疼痛患者对疼痛线索的动态注视偏向指标,并进一步考察这些指标对6个月后慢性疼痛强度和功能损伤变化的预测作用。研究发现,点探测视觉任务中,慢性疼痛患者在前3个时间窗上(0~500 ms、500~1000 ms、1000~1500 ms)对疼痛线索的注视偏向显著高于对中性线索的注视偏向,但在第四个时间窗上(1500~2000ms)不存在差异;融入真实疼痛刺激的视觉任务中,慢性疼痛患者在4个时间窗上对疼痛线索的注视偏向均显著高于对中性线索的注视偏向。分层标准多元回归模型和机器学习回归模型均发现,慢性疼痛患者在两个任务中对疼痛线索的晚期注视偏向(1000~1500ms、1500~2000ms两个时间窗),均可以独立预测6个月后慢性疼痛强度和功能损伤的维持。研究结果表明,尽管慢性疼痛患者对疼痛线索从注意早期就表现出注视偏向,但是只有晚期的注视偏向能够预测慢性疼痛的维持。

Pain-related attention biases have a crucial role in the development and maintenance of chronic pain.Previous meta-analyses have demonstrated that individuals with chronic pain exhibit a sustained attentional biases toward pain-related stimuli.Several studies have also highlighted associations between the maintenance of pain-related attention biases and poorer long-term chronic pain outcomes.However,traditional measures used in previous studies including total fixation or duration indexes,cannot capture the dynamic nature of attention or variability in attentional processes between individuals.Some researchers have suggested that the attentional biases associated with chronic pain may exist at different stages of attention processing.Therefore,in order to gain a deeper understanding of the dynamic nature of visual attention biases toward pain-related stimuli and their potential predictive effects on responses to chronic pain,this study employed a time window segmentation analysis of eye movement data.Additionally,real pain stimuli were utilized in the visual task to elicit more authentic responses.GPower3.1 was utilized to estimate the required sample size for this study;49 participants were needed to detect an effect size(f)of 0.17 with a significance level(α)of 0.05 and a power of 95%.A total of 94 participants(69 women)experiencing chronic musculoskeletal pain(e.g.,neck pain,shoulder pain,or low back pain),were recruited for this study.During the experiment,participants completed two tasks while their eye movements were recorded using an Eyelink 1000 eye tracker.The eye tracker had a sampling rate of 500 Hz,a spatial accuracy greater than 0.5°,and a resolution of 0.01°in the pupil-tracking mode.After receiving instructions,participants began the first task comprising 16 pairs of pain-neutral pictures and 16 pairs of neutral-neutral pictures,each measuring 11 cm×10 cm.The viewing angle of each picture was 8.99°×8.17°.In this task,picture pairs were displayed for 2000 ms,during which participants were instructed to freely view the pictures.Following the disappearance of the stimuli,a detection point appeared at the location of one of the pictures,and participants had to quickly and accurately judge the location of the detection point.Task 2 was identical to Task 1,exception that,no detection point was presented following the offset of picture pairs;instead,there was a possibility that an actual somatosensory pain stimulus would be delivered.Specifically,participants had a 25%chance of receiving a painful stimulus after each pain-neutral picture pair appeared while there was no chance a painful stimulus delivery after neutral-neutral picture pairs appeared.Participants were instructed to quickly and accurately determine whether or not they experienced a painful stimulus.At the start of the experiment,baseline data was collected,including the participants'chronic pain grade,pain catastrophizing scale scores,center for epidemiologic studies depression scores,and demographic information.Additionally,after a period of 6 months,the experimenters followed up with the participants to gather information on their chronic pain intensity and interference.Task 1 results revealed patients with chronic pain displayed attentional biases toward pain-related stimuli during the first three epochs(0~500 ms,500~1000 ms,and 1000~1500 ms).In Task 2,which incorporated real pain stimuli,participants exhibited attentional biases toward pain cues during all four epochs(0~500 ms,500~1000 ms,1000~1500 ms,and 1500~2000 ms).By examining the magnitude of attentional biases across the four time windows in the two tasks,it was evident that attentional biases toward pain-related stimuli in patients with chronic pain were imbalanced.Attention was engaged in the first epoch of stimulus presentation(0~500 ms),reached its peak during the second epoch(500~1000 ms),and then gradually decreased during the third and fourth epochs(1000~1500 ms and 1500~2000 ms).Further analysis revealed that attentional biases toward pain-related stimuli during the third and fourth epochs(1000~1500 ms and 1500~2000 ms)of both tasks independently predicted the maintenance of chronic pain intensity and interference levels at a six month follow-up.These effects were maintained even after controlling for baseline levels of pain intensity and interference and other baseline correlates of follow-up outcomes.The present study represents the first attempt to examine the impact of attentional bias towards pain-related stimuli on the maintenance of dysfunctional chronic pain outcomes from a dynamic perspective.These findings offer an explanation and valuable insights into attentional training,which holds significant importance in enhancing chronic pain management.Moving forward,training individuals to redirect their attention away from pain and associated cues during the later stages of attention may prove to be an effective approach for alleviating suffering due to chronic pain.