About this Research Topic
Excitability in the brain is modulated over several time scales in oscillations, whose incidence depends on brain state (e.g. rest vs alertness), area (e.g. primary vs higher cortical areas) and external stimulation (e.g. sensory stimulation or direct brain stimulation such as transcranial alternating current stimulation). Although many aspects of neuronal oscillations have been extensively studied, the implications and consequences of their exact frequency have received less attention. A commonly supported view states that oscillation frequency should not differ between networks to allow synchronization and should not vary over time to be useful as a reference frame in various computational schemes. Thus, frequency variation has been generally viewed as detrimental. However, recent empirical studies suggest that oscillation frequency variation over time, between states and between areas, is characteristic of biological systems. Here we explore an alternative view, supporting variability as a useful flexibility, which can be functionally exploited.
In this Research Topic, we argue and aim to collect research articles supporting the idea that the precise frequency of an oscillation has profound consequences on neuronal communication and cortical self-organization. First, we will welcome evidence that oscillation frequency is not hard-wired but is instead flexible, being dependent on the brain's input and state. We will then explore how such flexibility can be exploited functionally for selecting relevant sets of neurons, or for segregating single neurons, neuronal networks, or entire cortical regions, and for guiding information flow. We will show that frequency flexibility not only facilitates synchronization, and thus communication and integration, but can also prevent synchronization in a functionally beneficial manner. Finally, we will show that rhythmic stimulation (e.g., transcranial alternating current stimulation, tACS) at certain frequencies can produce reliable, predictable, and thus exploitable, downstream effects ranging from microscopic and mesoscopic network function to macroscopic behavioral states in both neurologically intact and impaired adults. We will argue that these processes, linked by their dependency on precise frequency differences, can be understood according to universal principles of synchronization as described extensively in physical systems and that applying this theory leads to a deeper understanding of the factors that define neuronal function, meso- and macroscopic communication, and eventually cognition and motor behavior.
We welcome papers, which in general demonstrate effects of exact oscillation frequencies and/or frequency variation on outcomes rooted at the neuronal, network, systems or behavioral levels. We are interested in both experimental or clinical electrophysiological studies and computational modelling studies. Further, electrophysiological studies demonstrating frequency-specific or frequency variation effects on synchronization, serving either functional integration or segregation are encouraged, as are larger scale computational models investigating such processes theoretically. Lastly, both theoretical and experimental studies using brain stimulation with specific frequencies, illustrating the effects at the neuronal, network or behavioral levels are highly relevant. We will generally welcome theoretical, experimental, and clinical original research papers, as well as reviews (e.g. systematic, mini, etc), methods, opinions, and perspectives on these topics.
Keywords: oscillations, frequency, synchronization, brain stimulation, networks
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