Attention Processing In Patients With Primary Insomnia And Habitual Short Sleepers: An Event-related Potential Study

Objective:Primary insomnia(PI)is a clinical disease characterized by difficulty initiating or maintaining sleep,waking up too early in the morning or non-restorative sleep,accompanied by symptoms such as fatigue,sleepiness,impaired attention,mood disruption(anxiety or depression)and memory deficits.As the prominent symptom,daytime function deficits impose a lot of burden for both the PI patients and the society.The mechanism underlying the deficits,however,remains unclear.And the current empirical studies failed to prove that PI patients have cognitive impairment.Habitual Short Sleepers(SS)are defined as those reporting < 6 h of sleep in their sleep diary.So far,there were few studies focused on the cognitive function in short sleepers.The existing studies supported that there were deficits in attention processing in the short sleepers.Event-related potentials(ERP)is widely used in exploring of cognitive processing of human brain.The P300 is a positive component of the ERP that peaks 300 ms or more(up to 900ms)after a stimulus.It can provide much fundamental information on the neural underpinnings of cognition.As a domain of cognition,attention can fall into two categories,including top-down attention and bottom-up attention.The novelty-P3 reflects bottom–up related aspect of attention,whereas the target-P3 reflects voluntary,top–down related aspect of attention.Detection of both novelty-P3 a and target-P3 b could provide new information concerning attention processing and the underlying neurophysiologic mechanisms.We use ERP and novelty oddball paradigm to investigate whether there were deficits in attention processing among patients with insomnia and healthy short sleepers.Method: 21 patients(PI),10 short sleepers(SS)and 24 good sleepers(GS)matched with age,sex and educational level.All of them were required to complete the ISI,PSQI,HAS,HAMA,HAMD and Epworth Sleepiness Scale.During the novelty oddball paradigm,all subjects were required to respond with a button press to the target tones only.Meanwhile their EEG and behavioral performance were recorded.The mean amplitude of novelty-P3 a and target-P3 b is measured respectively at F3,Fz,F4,C3,Cz,C4,P3,Pz,P4.The data were analysed using RMANOVEA.Linear correlations were performed between the magnitudes of the P300 for both subcomponents and HAMD,HAMA,ISI,PSQI,HAS,Reaction time and accuracy.Results:1.For the mean amplitude of novelty-P3 a,there was a significant main effect for group(novelty-P3a:F2,52 =3.701,P=0.03).Compared to GS group,PI group showed significant reduced mean amplitude of novelty-P3 a,while SS group showed no significant difference between GS group.There was a significant interact effect for region × group(F2.34,60.86 =4.033,P=0.018),post hoc showed that,compared to GS group,PI group showed significant reduced mean amplitude both in the frontal area(P=0.005)and the central area(P=0.032).2.For the mean amplitude of target-P3 b,there was a significant main effect for group(target-P3b:F2,53= 4.682,P=0.013).Compared to GS group,PI group showed significant reduced mean amplitude of target-P3 b,while SS group showed no significant difference between GS group.3.For the latency of novelty-P3 a,there was no significant main effect for group(F2,55=0.337,P=0.716).4.For the latency of target-P3 b,there was no significant main effect for group(F2,56=0.166,P=0.848).There was a significant interact effect for region × group(F2,56=3.992,P=0.024),post hoc showed that,latency in the frontal area was significantly longer than in the parietal area and the central area(P=0.022).5.There was no significant group difference in reaction time(F2,18= 0.085,P=0.919)and accuracy(F2,52= 1.707,P=0,191).6.There was no significant correlation between novelty-P3 a and target-P3 b and HAMD,HAMA,ISI,PSQI,HAS,Reaction time and accuracy in patients with primary insomnia.(P>0.05).Conclusion:1.Compared to GS,there was attention processing deficits in Patients with primary insomnia in a novelty oddball paradigm,while short sleepers 's showed no abnormal attention processing.2.There was no significant correlation between attention processing and the severity of PI patient,which indicated that novelty-P3 a and target-P3 b may be a disease-related index of primary insomnia,rather than state index.