Browsing by Subject "sleep spindle"

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  • Halonen, Risto; Kuula, Liisa; Lahti, Jari; Makkonen, Tommi; Räikkönen, Katri; Pesonen, Anu-Katriina (2019)
    A common single nucleotide polymorphism (SNP) of the brain-derived neurotrophic factor (BDNF) gene, Val66Met, has been reported to impair BDNF secretion and memory function. However, few studies have investigated the interaction of BDNF genotype and sleep characteristics, such as sleep spindles, that promote long-term potentiation during sleep. In this study we compared overnight visual memory between the carriers of BDNF Met and non-carriers (Val homozygotes), and examined how sleep spindle density associated with memory performance. The sample constituted of 151 adolescents (mean age 16.9 years; 69% Val homozygotes, 31% Met carriers). The learning task contained high and low arousal pictures from Interactive Affective Picture System. The learning task and all-night polysomnography were conducted at the homes of the adolescents. Slow (10–13 Hz) and fast (13–16 Hz) spindles were detected with automated algorithm. Neither post-sleep recognition accuracy nor spindle density differed between Val homozygotes and Met carriers. While frontal slow and fast spindle densities associated with better recognition accuracy in the entire sample, examining the allelic groups separately indicated paralleling associations in Val homozygotes only. Interaction analyses revealed a significant genotype-moderated difference in the associations between frontal fast sleep spindles and high arousal pictures. In sum, sleep spindles promote or indicate visual learning in Val homozygote adolescents but not in Met carriers. The result suggests that the role of sleep spindles in visual recognition memory is not equal across individuals but moderated by a common gene variant.
  • Pesonen, Anu-Katriina; Merikanto, Ilona; Halonen, Risto; Ujma, Peter; Makkonen, Tommi; Räikkönen, Katri; Lahti, Jari; Kuula, Liisa (2020)
    Sleep spindles are thalamocortical oscillations that contribute to sleep maintenanceand sleep-related brain plasticity. The current study is an explorative study of the cir-cadian dynamics of sleep spindles in relation to a polygenic score (PGS) for circadianpreference towards morningness. The participants represent the 17-year follow-upof a birth cohort having both genome-wide data and an ambulatory sleep electroen-cephalography measurement available (N= 154, Mean age = 16.9, SD = 0.1 years,57% girls). Based on a recent genome-wide association study, we calculated a PGSfor circadian preference towards morningness across the whole genome, including354 single-nucleotide polymorphisms. Stage 2 slow (9-12.5 Hz,N= 186 739) andfast (12.5-16 Hz,N= 135 504) sleep spindles were detected using an automatedalgorithm with individual time tags and amplitudes for each spindle. There was a sig-nificant interaction of PGS for morningness and timing of sleep spindles across thenight. These growth curve models showed a curvilinear trajectory of spindle ampli-tudes: those with a higher PGS for morningness showed higher slow spindle ampli-tudes in frontal derivations, and a faster dissipation of spindle amplitude in centralderivations. Overall, the findings provide new evidence on how individual sleep spin-dle trajectories are influenced by genetic factors associated with circadian type. Thefinding may lead to new hypotheses on the associations previously observedbetween circadian types, psychiatric problems and spindle activity.
  • Laitinen, Paavo (Helsingin yliopisto, 2022)
    Schizophrenia (SZ) is a neurodevelopmental psychiatric disorder with high heritability. Patients with SZ commonly suffer from sleep problems of different types, some of them with potential underlying abnormalities in sleep oscillations. These changes in sleep are usually accompanied by deficits in cognitive performance. However, the relationship between sleep, cognitive performance and genetic risk factors are not well known in SZ. In this study, patients were selected from a nation-wide SUPER -cohort. Sleep and circadian rhythm of patients with SZ (n = 26) and age-matched healthy controls (n = 11) were followed for a week with actigraphy and sleep diary, combined with word-pair -memory task and polysomnography at the end of the week. The results showed that patients spend more time in lighter sleep and awake during the night than controls. As expected, patients had impaired sleep spindle density compared to controls. Additionally, patient had worse overnight memory consolidation. However, sleep spindle density was not associated with memory performance. Lastly, polygenic risk score (PRS) for long sleep, but not PRS for SZ, predicted lower spindle density in patients, which could be indirect evidence for deviated neurophysiological processes of sleep behind the observed deviations in EEG oscillations among the patients. These results show that, as compared to controls, patients with SZ demonstrate abnormalities in their sleep, which can be seen both in macro- and microstructures of sleep. Further analyses of the interplay between sleep oscillations and genetic risk factors are likely needed to link sleep problems with overnight memory consolidation.
  • Halonen, Risto (Helsingfors universitet, 2017)
    Sleep spindles are thalamocortical oscillations that occupy the sigma band with trait-like inter-individual variability. Sleep spindles associate with reasoning abilities according to several studies, but some discrepancy exists in the strength and even direction of the associations. This may, to some extent, be due to methodological differences. The stage of brain maturation also affects spindle manifestation. In this community-based study, associations between spindle characteristics and reasoning abilities are examined in an understudied age group, adolescents. An all-night polysomnography was conducted at homes of 178 adolescents (104 girls). Working memory, visuospatial reasoning and verbal reasoning were measured in the same evening. An automatic algorithm was used to detect slow (10–13 Hz) and fast (13–16 Hz) spindles in frontal and central scalp derivations in NREM 2 sleep stage. The associations between spindle variables (density and intensity) and the cognitive test scores were analyzed with linear regression. Genders apart, the analyses were conducted first on the whole group and then separately on the Above Median (AM) and Below Median (BM) intelligence subgroups. In the analyses with all subjects, higher central fast density associated with better verbal reasoning in girls. When examining the subgroups separately, this association was not perceived in the AM group but appeared prominently in the BM group girls. No other associations were found between the spindle variables and the cognitive test scores. A positive spindle-intelligence relation is an established finding in females, but more commonly the association is typified by fluid/visuospatial reasoning and frontal brain areas. In the present study, young age may have related to the accentuated relative significance of more caudal brain regions and verbal intelligence in relation to spindles. The ongoing neural maturation and the heterogeneity of the sample may have contributed to the nature of the findings. More adolescent studies are needed to gain understanding of the matter.
  • Halonen, Risto; Kuula, Liisa; Antila, Minea; Pesonen, Anu-Katriina (2021)
    Accumulating evidence emphasizes the relevance of oscillatory synchrony in memory consolidation during sleep. Sleep spindles promote memory retention, especially when occurring in the depolarized upstate of slow oscillation (SO). A less studied topic is the inter-spindle synchrony, i.e. the temporal overlap and phasic coherence between spindles perceived in different electroencephalography channels. In this study, we examined how synchrony between SOs and spindles, as well as between simultaneous spindles, is associated with the retention of novel verbal metaphors. Moreover, we combined the encoding of the metaphors with respiratory phase (inhalation/exhalation) with the aim of modulating the strength of memorized items, as previous studies have shown that inhalation entrains neural activity, thereby benefiting memory in a waking condition. In the current study, 27 young adults underwent a two-night mixed-design study with a 12-h delayed memory task during both sleep and waking conditions. As expected, we found better retention over the delay containing sleep, and this outcome was strongly associated with the timing of SO–spindle coupling. However, no associations were observed regarding inter-spindle synchrony or respiratory phase. These findings contribute to a better understanding of the importance of SO–spindle coupling for memory. In contrast, the observed lack of association with inter-spindle synchrony may emphasize the local nature of spindle-related plasticity.