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Insomnia sufferers (INS) are cortically hyperaroused during sleep, which seems to translate into altered information processing during nighttime. While information processing, as measured by event-related potentials (ERPs), during wake appears to be associated with sleep quality of the preceding night, the existence of such an association during nighttime has never been investigated. This study aims to investigate nighttime information processing among good sleepers (GS) and INS while considering concomitant sleep quality. Following a multistep clinical evaluation, INS and GS participants underwent 4 consecutive nights of PSG recordings in the sleep laboratory. Thirty nine GS (mean age 34.56 ± 9.02) and twenty nine INS (mean age 43.03 ± 9.12) were included in the study. ERPs (N1, P2, N350) were recorded all night on Night 4 (oddball paradigm) during NREM sleep. Regardless of sleep quality, INS presented a larger N350 amplitude during SWS ( p = 0.042) while GS showed a larger N350 amplitude during late-night stage 2 sleep ( p = 0.004). Regardless of diagnosis, those who slept objectively well showed a smaller N350 amplitude ( p = 0.020) while those who slept subjectively well showed a smaller P2 ( p < 0.001) and N350 amplitude ( p = 0.006). Also, those who reported an objectively bad night as good showed smaller P2 ( p < 0.001) and N350 ( p = 0.010) amplitudes. Information processing seems to be associated with concomitant subjective and objective sleep quality for both GS and INS. However, INS show an alteration in information processing during sleep, especially for inhibition processes, regardless of their sleep quality. [ABSTRACT FROM AUTHOR]

Insomnia is a symptom, a syndrome and a comorbid disorder. Its diagnosis relies on subjective reports from the afflicted individual and is defined as difficulties in initiating sleep, maintaining sleep, waking up too early or non-restorative sleep. However, insomnia and especially, primary insomnia, has received much attention in insomnia research with the use of objective measures. Insomnia, its peculiarities, most frequent subtypes and two most prominent models will first be briefly introduced. Then, insomnia will be reviewed according to results obtained with the use of neurophysiological measures as basic/traditional as polysomnography to more sophisticated ones such as power spectral analysis, neuroimaging, cyclic alternating patterns and event-related potentials. In addition, a review of the discrepancies between subjective and objective reports of cognitive alterations through neuropsychological testing is offered. The need to combine measures is then highlighted in conclusion. [ABSTRACT FROM AUTHOR]

Abstract: Methylmercury (MeHg) and polychlorinated biphenyls (PCBs) are seafood contaminants known for their adverse effects on neurodevelopment. This study examines the relation of developmental exposure to these contaminants to information processing assessed with event-related potentials (ERPs) in school-aged Inuit children from Nunavik (Arctic Québec). In a prospective longitudinal study on child development, exposure to contaminants was measured at birth and 11 years of age. An auditory oddball protocol was administered at 11 years to measure ERP components N1 and P3b. Multiple regression analyses were performed to examine the associations of levels of the contaminants to auditory oddball performance (mean reaction time, omission errors and false alarms) and ERP parameters (latency and amplitude) after control for potential confounding variables. A total of 118 children provided useable ERP data. Prenatal MeHg exposure was associated with slower reaction times and fewer false alarms during the oddball task. Analyses of the ERP parameters revealed that prenatal MeHg exposure was related to greater amplitude and delayed latency of the N1 wave in the target condition but not to the P3b component. MeHg effects on the N1 were stronger after control for seafood nutrients. Prenatal PCB exposure was not related to any endpoint for sample as a whole but was associated with a decrease in P3b amplitude in the subgroup of children who had been breast-fed for less than 3 months. Body burdens of MeHg and PCBs at 11 years were not related to any of the behavioural or ERP measures. These data suggest that prenatal MeHg exposure alters attentional mechanisms modulating early processing of sensory information. By contrast, prenatal PCB exposure appears to affect information processing at later stages, when the information is being consciously evaluated. These effects seem to be mitigated in children who are breast-fed for a more extended period. [Copyright &y& Elsevier]

Abstract: Introduction: Our recent ERPs study suggested inhibition deficits in addition to cortical arousal in insomnia sufferers (INS) relative to good sleepers (GS). The aim of the present study was to investigate the relation between objective sleep parameters and the amplitudes and latencies of ERPs components N1 and P2 in a multi-assessment protocol. Methods: Participants, 15 INS and 16 GS, underwent four consecutive nights of polysomnography recordings (N1 to N4). ERPs in the evening and upon awakening were recorded on N3 and N4, with the addition of sleep-onset recordings on N4. Auditory stimuli consisted of ‘standard’ and ‘deviant’ tones. Objective sleep measures were computed on each night [sleep efficiency (SE), wake after sleep onset (WASO), total sleep time (TST) and sleep-onset latency (SOL)]. The amplitude and latency of N1 and P2 components were assessed for each recorded session on each night and related to measures of sleep of the same nights (N3 and N4). Results: Pearson''s correlations between the amplitude and latency of N1 and P2 and objective sleep measures revealed that arousal levels in the evening, before going to bed seem to have an impact on subsequent sleep quality. Furthermore, the sleep quality of the previous night also appeared to have an impact on morning (daily) arousal levels. Conclusion: These results suggest that hyperactivation and inhibition deficits present in insomnia sufferers are directly associated with a poorer sleep quality. This highlights once again that when information processing and/or performance is assessed, the sleep quality of the night preceding the evaluation shall be documented. [Copyright &y& Elsevier]

Abstract: Preliminary QEEG studies suggest that individuals with paradoxical insomnia (Para-I) display higher cortical arousal than those with psychophysiological insomnia (Psy-I). Lately, finer measures, such as event-related potentials, and especially the N1 and P2 components have been used to document arousal processes in individuals with insomnia. The objective of the present study was to further circumscribe arousal in Psy-I and Para-I using N1, P2 and the waking processing negativity (wPN). N1 and P2 were recorded in the evening, at sleep-onset and in early stage 2 sleep in 26 good sleepers, 26 Psy-I and 26 Para-I. An oddball paradigm was used and participants received the instruction to ignore all stimuli at all times. Three difference waves (wPNs) were computed to evaluate the transition from wakefulness to sleep onset, from sleep onset to sleep and from wakefulness to sleep. Results revealed that N1 was smaller during wakefulness and sleep onset for Psy-I, while it was larger for Para-I during these same times. P2 was smaller at sleep onset for Psy-I than for Para-I and GS, while P2 during wakefulness and stage 2 sleep was larger for Para-I than GS. WPNs revealed that Psy-I showed fewer changes in information processing, while Para-I showed larger changes between recording times. Psy-I appear to present an inability to inhibit information processing during sleep onset, while Para-I seem to present overall enhanced attentional processing that results in a greater need for inhibition. [Copyright &y& Elsevier]

Abstract: The event-related potential (ERP) P3b, a cognitive electrophysiological measure that has been linked to working memory processing in many experimental paradigms, was measured in Inuit children from Nunavik (Arctic Québec, Canada) to assess lead (Pb) neurotoxicity. Visual and auditory oddball paradigms were administered at 5 (N =27) and 11 (N =110) years of age, respectively, to elicit this ERP component. Pearson correlations and multiple regression analyses were performed to examine the associations between Pb levels and P3b parameters (peak latency and amplitude). Greater prenatal Pb exposure was related to a decrease in P3b amplitude at 5 years of age, and early childhood Pb exposure was associated with delayed P3b latency at 5 years. No significant association was observed at 11 years. These results, in line with those from previous neurobehavioral studies, suggest that Pb exposure affects cognitive processing in children even though the Pb levels measured in a large majority of our sample were below the threshold value for public health intervention used by federal agencies. This study strengthens the arguments for reducing sources of Pb exposure in Nunavik and for lowering the blood Pb concentrations considered “acceptable” in governmental policies. [Copyright &y& Elsevier]