Effects Of Pain-ralated Traits On Fear Generalization

Background and ObjectiveFear generalization involves transferring the fear response from a threatening stimulus to a novel stimulus similar to the original one.Fear generalization has been proven to contribute to the development and maintenance of pain.In addition,individuals show differences in the level of pain sensitivity.There still remains unclear whether such differences would cause different performance in the fear generalization.The purpose of this study is to explore the fear generalization performance of individuals with different pain sensitivity and individuals in pain state,so as to provide a basis for further research on the development and maintenance of pain.MethodsIn study 1,healthy individuals were divided into high and low pain sensitivity groups according to the scores of the pain sensitivity questionnaire.A total of fortyfour subjects participated in the experiment by randomly recruiting in the two groups.The pain-related fear acquisition was established by giving electrical stimulation.Behavioral data were recorded during the acquisition phase,and both behavioral and event-related potential(ERP)data were recorded during the generalization phase,in order to study whether individuals with different pain sensitivity traits effects their performance on fear generalization paradigm.In Study 2,23 healthy participants under experimental pain as experimental group and 23 matched non-pain controls as control group,learned fear conditioning and then completed the fear generalization paradigm combined with the perceptual categorization task.Behavioral and EEG data were recorded during the experiment.The purpose of this study is to explore whether there were perceptual bias in individuals with pain and whether such bias could lead to excessive fear generalization.ResultsIn study 1,during the acquisition phase,the fear response to the dangerous conditioned stimulus(CS+)of the two groups were higher than those to the safe conditioned stimulus(CS-)(all P<0.05).Compared with the low pain sensitivity group,the high pain sensitivity group showed higher fear response(all P<0.05).The ERP results showed that compared with the low pain sensitivity group,the high pain sensitivity group showed a larger LPP amplitude(P<0.05)and a slightly increased P1 amplitude(P=0.058),while the N1 component showed a smaller amplitude(P<0.05).In study 2,both experimental and control groups had fear response for CS+than for CS-in the acquisition phase(P<0.05).In the generalization phase,subjects in both groups scored CS+and GS higher than CS-(all P<0.05).Compared with the control group,the experimental group were more likely to judge GS as CS+(P<0.05).When the stimulus was judged as CS+,the fear response for all stimuli were significantly stronger than those in the GS category(P<0.001).ERP results showed that compared with the control group,the experimental group showed an earlier N1 latency and smaller P1 and LPP amplitudes(all P<0.05).ConclusionDifferent trait of pain sensitivity have an effect on fear generalization.Healthy individuals with high pain sensitivity have a tendency to be overgeneralization of pain-related fear and have stronger fear responses to dangerous and generalized stimuli,which leads to an increase in LPP amplitude and a slight increase in P1 amplitude during the execution of the fear generalization task.This may be due to the fact that healthy people with high pain sensitivity are more fearful of pain-related dangerous stimuli and thus allocated more attention.Individuals with experimental pain was found a perceptual discrimination bias,which tends to judge the generalized stimulus as a threat stimulus,and this misjudgment can lead to a greater fear response to the generalization stimulus,which in turn produces excessive fear generalization.The fear response is also manifested as a decrease in N1 latency and an increase in P1 and LPP amplitude.Such differences may be that healthy individuals under pain tend to increase vigilance to pain-related stimulus,and such pain condition will interfere with the allocation of attention,leading to a reduction in the recruitment of attention resources.