Novel Stimulus Processing In Primary Insomnia Patients And Habitual Short Sleepers Under The Pre-attention Condition: An Event-related Potential Study

Objective:Insomnia is defined as a complaint of prolonged sleep latency,difficulties in maintaining sleep,the experience of non-refreshing or poor sleep coupled with impariments of daytime functioning,including reduced alertness,fatigue,exhaustion,dysphoria and other symptoms.Primary insomnia(PI)is the insomnia excluding other diseases or substance misuse.The pathophysiological mechanism of insomnia is still unknown.Most scholars believe that hyperarousal is crucial for causing insomnia,but relatively little research focused on its information processing.There is a dispute over the pre-attention processing.Habitual short sleepers(SS)are defined as those reporting < 6 h of sleep in their sleep diary.Little attention was paid on this population,although the prevalence of SS is gradually increasing.Existing research shows its novel stimulus processing is abnormal.The aim of this experiment is to investigate the pre-attentive and attention orienting response processing of novel stimulus in PI patients and SS by Event-Related Potential(ERP)technology.The ERP component we analys is Mismatch Negativity(MMN)and P3 a.Besides,we want to explore whether amplitudes of MMN and P3 a correlated with their hyperarousal level.Method:23 patients with primary insomnia(PI),10 habitual short sleepers(SS)and 15 healthy good sleepers(GS)were matched in sex and age.All patients meet the cirteria for primary insomnia in DSM-IV.All subjects completed the Hamilton Anxiety Scale(HAMA),Hamilton Depression Scale(HAMD),Pittsburgh Sleep Quality Index Scale(PSQI),Insomnia Severity Scale(ISI),Hyperarousal Scale(HAS)and Epworth Sleepiness Scale(ESS)before recording EEG.We utilized a novelty oddbal paradigm and stimuli consisted of “standard” tones(pure tone=600Hz,80%),“deviant” tones(pure tone=700Hz,10%)and “novel” sounds(80 environmental sounds,10%).During the experiment all subjects were asked to watching a silent movie and ignoring the sounds from headphone.The MMN and P3 a amplitudes and latencies were obtained at frontal electrodes(F3,Fz,F4)and central electrodes(C3,Cz,C4).The data was analyzed with repeated measures analyses of variance(RANOVA).Pearson correlation was used to assess the correlation between amplitudes of MMN and P3 a and scores on HAS in PI patients.Results:1.No main effects of group were found in the MMN amplitude(F(2,50)=0.490,p=0.615),but there was a significant region × hemisphere × group interaction effect(F(4,100)=2.868,p<0.05).Further analysis showed that in the GS group: the left frontal region lower than the middle frontal region(p=0.011),the left central region lower than the middle central region(p=0.003)and the left central region lower than the right central region(p=0.023).While in the SS group,lower MMN amplitude in the middle frontal region than the middle central region(p=0.028).2.No main effects of group were found in the P3 a amplitude(F(2,50)=0.387,p=0.681),but there was a significant region × group interaction(F(2,50)=9.504,p<0.01).Further analysis showed that amplitudes of P3 a were much higher in the frontal region than that in the central region in the GS group(p<0.01)and SS group(p<0.01).3.No main effects of group were found in the MMN latency(F(2,50)=0.128,p=0.880).4.Main effects of group were found in the P3 a latency(F(2,50)=8.121,p<0.01).Compared to NS group,PI group showed significant prolonged latency of P3a(p<0.01).The SS group showed no significant difference between NS group and PI group(ps>0.05).5.There was no significant correlation between amplitudes of MMN and P3 a and scores on HAS in PI patients(ps>0.05).Conclusion:Patients with primary insomnia exhibited no significant deficit in pre-attention processing to novel stimulus.The amplitude of the orienting response processing was not abnormal,and the latency was prolonged in PI patients.The habitual short sleepers show no significant deficits in novel stimulus processing.There is an abnormal distribution of hemisphere among PI patients at novel stimulus processing.There was no significant correlation between amplitudes of MMN and P3 a and hyperarousal level in PI patients.