The effect of experimental pain on attentional bias in a pictorial dot-probe task

Abstract

Objective To investigate the effect of moderate pain on attentional bias towards emotional pictures among healthy subjects.Methods Thirty-two healthy college students aged from 17 to 26 (21.8±2.2;16 males and 16 females) participated in this study.A tourniquet was tied to each subject's left upper arm 1 to 2cm above the cubits horizontal grain.Pain was inflicted by inflating the tourniquet,and the pressure was maintained at 26.66kPa.While tourniquet was inflated (with pain) or not (no pain),each subject was asked to finish a pictorial dot-probe task with three kinds of pictures-emotionally positive,negative and neutral.In experiment 1,subjects performed the dot-probe tasks with the contralateral hand while the tourniquet was tied on the left upper arm without inflation.In experiment 2 the tourniquet was inflated until the subject completed the dot-probe task (for about 10min).The reaction times (RTs) and the error rates (Ers) in the recognition task were recorded,and the intensity of the subject's pain and discomfort were measured using a verbal rating scale.Results The subjects reported moderate to severe pain with the tourniquet inflated.The RT and ER data were analyzed using two-way analysis of variance (ANOVA) which showed a significant difference between the average RTs of the males (482±73ms without pain and 466±82ms with pain) and those of the females (536±90ms without pain and 519±100 ms with pain).The average ER was significantly different between the pain (2.38±1.49)％ and no pain (1.09±0.82)％ conditions in both groups.Holn-Sidak multiple comparison testing showed significant differences in both groups' average ER between the negative picture (3.81±1.73)％ and the positive picture (1.66±0.97)％,and between the negative and neutral pictures (1.68±0.8) ％ in the pain condition.Mild attentional avoidance was observed with the positive [pain condition (-5.1±4.8) ms and no pain (-4.6±4)ms] and negative pictures [pain condition (-3.43±6) ms and no pain (-0.79±4.1)ms],but no significant difference was found between the pain and no pain conditions.Conclusion The error rate in a pictorial dot-probe task is influenced by pain,especially with negative pictures. Key words: Pain; Attentional bias; Emotional pictures; Dot-probe tasks