Browsing by Subject "SYNCHRONY"

Sort by: Order: Results:

Now showing items 1-9 of 9
  • Antao, Laura H.; Pöyry, Juha; Leinonen, Reima; Roslin, Tomas (2020)
    Aim Biodiversity is currently undergoing rapid restructuring across the globe. However, the nature of biodiversity change is not well understood, as community-level changes may hide differential responses in individual population trajectories. Here, we quantify spatio-temporal community and stability dynamics using a long-term high-quality moth monitoring dataset. Location Finland, Northern Europe. Time period 1993-2012. Major taxa studied Nocturnal moths (Lepidoptera). Methods We quantified patterns of change in species richness, total abundance, dominance and temporal variability at different organizational levels over a 20 year period and along a latitudinal gradient of 1,100 km. We used mixed-effects and linear models to quantify temporal trends for the different community and stability metrics and to test for latitudinal (or longitudinal) effects. Results We found contrasting patterns for different community metrics, and strong latitudinal patterns. While total moth abundance has declined, species richness has simultaneously increased over the study period, but with rates accelerating with latitude. In addition, we revealed a latitudinal pattern in temporal variability-the northernmost locations exhibited higher variability over time, as quantified by both metrics of richness and aggregated species population trends. Main conclusions When combined, our findings likely reflect an influx of species expanding their ranges poleward in response to warming. The overall decline in abundance and the latitudinal effect on temporal variability highlight potentially severe consequences of global change for community structure and integrity across high-latitude regions. Importantly, our results underscore that increases in species richness may be paralleled by a loss of individuals, which in turn might affect higher trophic levels. Our findings suggest that the ongoing global species redistribution is affecting both community structure and stability over time, leading to compounded and partly opposing effects of global change depending on which biodiversity dimension we focus on.
  • Arstila, Valtteri; Georgescu, Alexandra L.; Lunn, Daniel; Noreika, Valdas; Falter-Wagner, Christine M.; Pesonen, Henri (2020)
    Essential for successful interaction with the environment is the human capacity to resolve events in time. Typical event timing paradigms are judgements of simultaneity (SJ) and of temporal order (TOJ). It remains unclear whether SJ and TOJ are based on the same underlying mechanism and whether there are fixed thresholds for resolution. The current study employed four visual event timing task versions: horizontal and vertical SJ and TOJ. Binary responses were analysed using multilevel binary regression modelling. Modulatory effects of potential explanatory variables on event timing perception were investigated: (1) Individual factors (sex and age), (2) temporal factors (SOA, trial number, order of experiment, order of stimuli orientation, time of day) and (3) spatial factors (left or right stimulus first, top or bottom stimulus first, horizontal vs. vertical orientation). The current study directly compares for the first time, performance on SJ and TOJ tasks using the same paradigm and presents evidence that a variety of factors and their interactions selectively modulate event timing functions in humans, explaining the variance found in previous studies. We conclude that SJ and TOJ are partially independent functions, because they are modulated differently by individual and contextual variables.
  • Wang, Sheng H.; Lobier, Muriel; Siebenhuhner, Felix; Puoliväli, Tuomas; Palva, Satu; Palva, J. Matias (2018)
    Inter-areal functional connectivity (FC), neuronal synchronization in particular, is thought to constitute a key systems-level mechanism for coordination of neuronal processing and communication between brain regions. Evidence to support this hypothesis has been gained largely using invasive electrophysiological approaches. In humans, neuronal activity can be non-invasively recorded only with magneto-and electroencephalography (MEG/EEG), which have been used to assess FC networks with high temporal resolution and whole-scalp coverage. However, even in source-reconstructed MEG/EEG data, signal mixing, or "source leakage", is a significant confounder for FC analyses and network localization. Signal mixing leads to two distinct kinds of false-positive observations: artificial interactions (AI) caused directly by mixing and spurious interactions (SI) arising indirectly from the spread of signals from true interacting sources to nearby false loci. To date, several interaction metrics have been developed to solve the AI problem, but the SI problem has remained largely intractable in MEG/EEG all-to-all source connectivity studies. Here, we advance a novel approach for correcting SIs in FC analyses using source-reconstructed MEG/EEG data. Our approach is to bundle observed FC connections into hyperedges by their adjacency in signal mixing. Using realistic simulations, we show here that bundling yields hyperedges with good separability of true positives and little loss in the true positive rate. Hyperedge bundling thus significantly decreases graph noise by minimizing the false-positive to true-positive ratio. Finally, we demonstrate the advantage of edge bundling in the visualization of large-scale cortical networks with real MEG data. We propose that hypergraphs yielded by bundling represent well the set of true cortical interactions that are detectable and dissociable in MEG/EEG connectivity analysis.
  • Marchi, Viviana; Stevenson, Nathan; Koolen, Ninah; Mazziotti, Raffaele; Moscuzza, Francesca; Salvadori, Stefano; Pieri, Rossella; Ghirri, Paolo; Guzzetta, Andrea; Vanhatalo, Sampsa (2020)
    Early nutritional compromise after preterm birth is shown to affect long-term neurodevelopment, however, there has been a lack of early functional measures of nutritional effects. Recent progress in computational electroencephalography (EEG) analysis has provided means to measure the early maturation of cortical activity. Our study aimed to explore whether computational metrics of early sequential EEG recordings could reflect early nutritional care measured by energy and macronutrient intake in the first week of life. A higher energy or macronutrient intake was assumed to associate with improved development of the cortical activity. We analyzed multichannel EEG recorded at 32 weeks (32.4 ± 0.7) and 36 weeks (36.6 ± 0.9) of postmenstrual age in a cohort of 28 preterm infants born before 32 weeks of postmenstrual age (range: 24.3–32 weeks). We computed several quantitative EEG measures from epochs of quiet sleep (QS): (i) spectral power; (ii) continuity; (iii) interhemispheric synchrony, as well as (iv) the recently developed estimate of maturational age. Parenteral nutritional intake from day 1 to day 7 was monitored and clinical factors collected. Lower calories and carbohydrates were found to correlate with a higher reduction of spectral amplitude in the delta band. Lower protein amount associated with higher discontinuity. Both higher proteins and lipids intake correlated with a more developmental increase in interhemispheric synchrony as well as with better progress in the estimate of EEG maturational age (EMA). Our study shows that early nutritional balance after preterm birth may influence subsequent maturation of brain activity in a way that can be observed with several intuitively reasoned and transparent computational EEG metrics. Such measures could become early functional biomarkers that hold promise for benchmarking in the future development of therapeutic interventions.
  • Stevanovic, Melisa; Tuhkanen, Samuel; Järvensivu, Milla; Koskinen, Emmi; Savander, Enikö; Valkia, Kaisa (2021)
    A novel conversation-analytically informed paradigm was used to examine how joint decision-making interaction, with its various types of proposal sequences, is reflected in the physiological responses of participants. Two types of dyads–dyads with one depressed and one non-depressed participant (N = 15) and dyads with two non-depressed participants (N = 15)–engaged in a series of conversational joint decision-making tasks, during which we measured their skin conductance (SC) responses. We found that the participants’ SC response rates were higher and more synchronized during proposal sequences than elsewhere in the conversation. Furthermore, SC response rates were higher when the participant was in the role of a proposal speaker (vs. a proposal recipient), and making a proposal was associated with higher SC response rates for participants with depression (vs. participants without depression). Moreover, the SC response rates in the proposal speaker were higher when the recipient accepted (vs. not accepted) the proposal. We interpret this finding with reference to accepting responses suggesting a commitment to future action, for which the proposal speaker may feel specifically responsible for. A better understanding of the physiological underpinnings of joint decision-making interaction may help improve democratic practices in contexts where certain individuals experience challenges in this regard.
  • Tokariev, Anton; Stjerna, Susanna; Lano, Aulikki; Metsäranta, Marjo; Palva, J. Matias; Vanhatalo, Sampsa (2019)
    Preterm birth is the greatest risk factor for lifelong neurocognitive deficits, globally. The effect of prematurity on early cortical network function has, however, remained poorly understood. Here, we developed a novel methodology that allows reliable assessment of functional connectivity in neonatal brain activity at millisecond and multisecond scales in terms of cortical phase and amplitude correlations, respectively. We measured scalp electroencephalography at term-equivalent age in infants exposed to very early prematurity as well as in healthy controls. We found that newborn cortical activity organizes into multiplex networks that differ significantly between vigilance states. As compared with healthy control infants, prematurity was found to cause frequency-specific patterns of dysconnectivity in cortical network, changes that were distinct for networks of phase and amplitude correlations. Neuroanatomically, the most prominent markers of prematurity were found in connections involving the frontal regions. Phase synchrony in frontally connected networks was correlated with newborn neurological performance, suggesting the first measure of cortical functional coupling that correlates with neurological performance in human infant.
  • Stevanovic, Melisa; Himberg, Tommi; Niinisalo, Maija; Kahri, Mikko; Peräkylä, Anssi; Sams, Mikko; Hari, Riitta (2017)
    We studied behavioral matching during joint decision making. Drawing on motion-capture and voice data from 12 dyads, we analyzed body-sway and pitch-register matching during sequential transitions and continuations, with and without mutual visibility. Body sway was matched most strongly during sequential transitions in the conditions of mutual visibility. Pitch-register matching was higher during sequential transitions than continuations only when the participants could not see each other. These results suggest that both body sway and pitch register are used to manage sequential transitions, while mutual visibility influences the relative weights of these two resources. The conversational data are in Finnish with English translation.
  • Tiippana, Kaisa; Salmela, Viljami R. (2018)
    Some classical studies on temporal order judgments (TOJ) suggested a single central process comparing stimulus onsets across modalities. The prevalent current view suggests that there is modality-specific timing estimation followed by a cross-modal stage. If the latter view is correct, TOJ's may vary depending on stimulus modality. Further, if TOJ is based only on onsets, stimulus duration should be irrelevant. To address these issues, we used both unisensory and multisensory stimuli to test whether unisensory duration processing influences cross-modal TOJ's. The stimuli were auditory noise bursts, visual squares, and their cross-modal combinations presented at 10, 40 and 500 ms durations, and various stimulus onset asynchronies. Psychometric functions were measured with an identical task in all conditions: On each trial, two stimuli were presented, one to the left, the other to the right of fixation. The participants judged which one started first. TOJ's were little affected by stimulus duration, implying that they are mainly determined by stimulus onsets. Throughout, the cross-modal just noticeable differences were larger than the unisensory ones. In accordance with the current view, our results suggest that cross-modal TOJ's require a comparison of timing after modality-specific estimations.
  • 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.