Browsing by Subject "synchronization"

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  • Kurunmäki, Jussi Antero; Marjanen, Jani (2021)
    The creation of Finland as a grand duchy within the Russian Empire in 1809 opened up the question of what Finland was, in fact. Comparing Finland synchronously with other countries and diachronically with itself before and after its elevation into a grand duchy gained temporal features in which its level of development was assessed. Such temporal comparisons during the first half of the 19th century were used to shape Finland as a political unit, as they facilitated assessment of which parts of society needed to improve in order to make the country comparable with imagined or real others. Given that the Diet (the Estate Assembly) was not convened between 1809 and 1863, these comparative notions largely dealt with questions of political constitution and state institutions. The comparative mindset of the Finnish actors also developed in the process of conducting temporal comparisons. These comparisons can be analyzed through the analytical categories of descriptive synchronization, comparative synchronization, and participative synchronization, the last mentioned being possible only when Finnish actors began to think that Finland, indeed, had developed to a level of maturity.
  • Palva, J. Matias; Palva, Satu (2018)
    Neuronal oscillations and their inter-areal synchronization may be instrumental in regulating neuronal communication in distributed networks. Several lines of research have, however, shown that cognitive tasks engage neuronal oscillations simultaneously in multiple frequency bands that have distinct functional roles in cognitive processing. Gamma oscillations (30-120Hz) are associated with bottom-up processing, while slower oscillations in delta (1-4Hz), theta (4-7Hz), alpha (8-14Hz) and beta (14-30Hz) frequency bands may have roles in executive or top-down controlling functions, although also other distinctions have been made. Identification of the mechanisms that integrate such spectrally distributed processing and govern neuronal communication among these networks is crucial for understanding how cognitive functions are achieved in neuronal circuits. Cross-frequency interactions among oscillations have been recognized as a likely candidate mechanism for such integration. We advance here the hypothesis that phase-phase synchronization of neuronal oscillations in two different frequency bands, cross-frequency phase synchrony (CFS), could serve to integrate, coordinate and regulate neuronal processing distributed into neuronal assemblies concurrently in multiple frequency bands. A trail of studies over the past decade has revealed the presence of CFS among cortical oscillations and linked CFS with roles in cognitive integration. We propose that CFS could connect fast and slow oscillatory networks and thereby integrate distributed cognitive functions such as representation of sensory information with attentional and executive functions.
  • Rouhinen, Santeri; Siebenhühner, Felix; Palva, J. Matias; Palva, Satu (2020)
    The capacity of visual attention determines how many visual objects may be perceived at any moment. This capacity can be investigated with multiple object tracking (MOT) tasks, which have shown that it varies greatly between individuals. The neuronal mechanisms underlying capacity limits have remained poorly understood. Phase synchronization of cortical oscillations coordinates neuronal communication within the fronto-parietal attention network and between the visual regions during endogenous visual attention. We tested a hypothesis that attentional capacity is predicted by the strength of pretarget synchronization within attention-related cortical regions. We recorded cortical activity with magneto- and electroencephalography (M/EEG) while measuring attentional capacity with MOT tasks and identified large-scale synchronized networks from source-reconstructed M/EEG data. Individual attentional capacity was correlated with load-dependent strengthening of theta (3-8 Hz), alpha (8-10 Hz), and gamma-band (30-120 Hz) synchronization that connected the visual cortex with posterior parietal and prefrontal cortices. Individual memory capacity was also preceded by crossfrequency phase-phase and phase-amplitude coupling of alpha oscillation phase with beta and gamma oscillations. Our results show that good attentional capacity is preceded by efficient dynamic functional coupling and decoupling within brain regions and across frequencies, which may enable efficient communication and routing of information between sensory and attentional systems.