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  • Rozov, Stanislav V.; Zant, Janneke; Gurevicius, Kestutis; Porkka-Heiskanen, Tarja; Panula, Pertti (2016)
    Aim: Under natural conditions diurnal rhythms of biological processes of the organism are synchronized with each other and to the environmental changes by means of the circadian system. Disturbances of the latter affect hormonal levels, sleep-wakefulness cycle and cognitive performance. To study mechanisms of such perturbations animal models subjected to artificial photoperiods are often used. The goal of current study was to understand the effects of circadian rhythm disruption, caused by a short light-dark cycle regime, on activity of the cerebral cortex in rodents. Methods: We used electroencephalogram to assess the distribution of vigilance states, perform spectral analysis, and estimate the homeostatic sleep drive. In addition, we analyzed spontaneous locomotion of C57BL/6J mice under symmetric, 22-, 21-, and 20-h-long light-dark cycles using video recording and tracking methods. Results and Conclusions: We found that shortening of photoperiod caused a significant increase of slow wave activity during non-rapid eye movement sleep suggesting an elevation of sleep pressure under such conditions. While the rhythm of spontaneous locomotion was completely entrained by all light-dark cycles tested, periodic changes in the power of the theta- and gamma-frequency ranges during wakefulness gradually disappeared under 22- and 21-h-long light-dark cycles. This was associated with a significant increase in the theta-gamma phase-amplitude coupling during wakefulness. Our results thus provide deeper understanding of the mechanisms underlying the impairment of learning and memory retention, which is associated with disturbed circadian regulation.
  • Kovanen, Leena; Donner, Kati; Kaunisto, Mari; Partonen, Timo (2016)
    Cryptochromes are key components of the circadian clocks that generate and maintain seasonal variations. The aim of our study was to analyze the associations of CRY1 and CRY2 genetic variants with the problematicity of seasonal variations, and whether the problematicity of seasonal variations changed during the follow-up of 11 years. Altogether 21 CRY1 and 16 CRY2 single-nucleotide polymorphisms (SNPs) were genotyped and analyzed in 5910 individuals from a Finnish nationwide population-based sample who had filled in the self-report on the seasonal variations in mood and behavior in the year 2000. In the year 2011, 3356 of these individuals filled in the same self-report on the seasonal variations in mood and behavior. Regression models were used to test whether any of the SNPs associated with the problematicity of seasonal variations or with a change in the problematicity from 2000 to 2011. In the longitudinal analysis, CRY2 SNP rs61884508 was protective from worsening of problematicity of seasonal variations. In the cross-sectional analysis, CRY2 SNP rs72902437 showed evidence of association with problematicity of seasonal variations, as did SNP rs1554338 (in the MAPK8IP1 and downstream of CRY2). (C) 2016 Elsevier Ireland Ltd. All rights reserved.
  • Kovanen, Leena; Kaunisto, Mari; Donner, Kati; Saarikoski, Sirkku T.; Partonen, Timo (2013)
  • Elovainio, Marko; Komulainen, Kaisla; Lipsanen, Jari; Partonen, Timo; Pesonen, Anu Katriina; Pulkki-Råback, Laura; Paunio, Tiina; Kähönen, Mika; Vahtera, Jussi; Virtanen, Marianna; Ruuhela, Reija; Hakulinen, Christian; Raitakari, Olli (2022)
    We analysed (A) the association of short-term as well as long-term cumulative exposure to natural light, and (B) the association of detailed temporal patterns of natural light exposure history with three indicators of sleep: sleep duration, sleep problems, and diurnal preference. Data (N = 1,962; 55% women; mean age 41.4 years) were from the prospective Young Finns Study, which we linked to daily meteorological data on each participant’s neighbourhood natural light exposure using residential postal codes. Sleep outcomes were self-reported in 2011. We first examined associations of the sleep outcomes with cumulative light exposure of 5-year, 2-year, 1-year, and 2-month periods prior to the sleep assessment using linear and Poisson regression models adjusting for potential confounders. We then used a data-driven time series approach to detect clusters of participants with different light exposure histories and assessed the associations of these clusters with the sleep outcomes using linear and Poisson regression analyses. A greater cumulative light exposure over ≥1 year was associated with a shorter sleep duration (β = −0.10, 95% confidence interval [CI] −0.15 to −0.04), more sleep problems (incident rate ratio [IRR] 1.04, 95% CI 1.0–1.07) and diurnal preference towards eveningness (β = −0.09, 95% CI −0.14 to −0.03). The data-driven exposure pattern of “slowly increasing” light exposure was associated with fewer overall sleep problems (IRR 0.93, 95% CI 0.88–0.98) compared to a “recently declining” light exposure group representing the “average-exposure” group. These findings suggest that living in an area with relatively more intense light exposure for a longer period of time influences sleep.
  • Utge, Siddheshwar; Soronen, Pia; Loukola, Anu; Kronholm, Erkki; Ollila, Hanna M.; Pirkola, Sami; Porkka-Heiskanen, Tarja; Partonen, Timo; Paunio, Tiina (2010)
  • Kohtala, S.; Alitalo, O.; Rosenholm, M.; Rozov, S.; Rantamäki, T. (2021)
    Several studies have demonstrated the effectiveness of ketamine in rapidly alleviating depression and suicidal ideation. Intense research efforts have been undertaken to expose the precise mechanism underlying the antidepressant action of ketamine; however, the translation of findings into new clinical treatments has been slow. This translational gap is partially explained by a lack of understanding of the function of time and circadian timing in the complex neurobiology around ketamine. Indeed, the acute pharmacological effects of a single ketamine treatment last for only a few hours, whereas the antidepressant effects peak at around 24 hours and are sustained for the following few days. Numerous studies have investigated the acute and long-lasting neurobiological changes induced by ketamine; however, the most dramatic and fundamental change that the brain undergoes each day is rarely taken into consideration. Here, we explore the link between sleep and circadian regulation and rapid -acting antidepressant effects and summarize how diverse phenomena associated with ketamine's antidepressant actions - such as cortical excitation, synaptogenesis, and involved molecular determinants - are intimately connected with the neurobiology of wake, sleep, and circadian rhythms. We review several recently proposed hypotheses about rapid antidepressant actions, which focus on sleep or circadian regulation, and discuss their implications for ongoing research. Considering these aspects may be the last piece of the puzzle necessary to gain a more comprehensive understanding of the effects of rapid-acting antidepressants on the brain. (c) 2020 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://