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simulation data from lattice phase-oscillator model part 2... simulation data from lattice phase-oscillator model part 4... simulation data from lattice phase-oscillator model part 5... simulation data from lattice phase-oscillator model part 6... gamma oscillation... Matlab Code of a ring-shaped phase-oscillator model (Fig.6)
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Recently, we reported evidence for a novel mechanism of peripheral sensory coding based on oscillatory synchrony. Spontaneously oscillating electroreceptors in weakly electric fish (Mormyridae) respond to electrosensory stimuli with a phase reset that results in transient synchrony across the receptor population (Baker et al., 2015). Here, we asked whether the central electrosensory system actually detects the occurrence of synchronous oscillations among receptors. We found that electrosensory stimulation elicited evoked potentials in the midbrain exterolateral nucleus at a short latency following receptor synchronization. Frequency tuning in the midbrain resembled peripheral frequency tuning, which matches the intrinsic oscillation frequencies of the receptors. These frequencies are lower than those in individual conspecific signals, and instead match those found in collective signals produced by groups of conspecifics. Our results provide further support for a novel mechanism for sensory coding based on the detection of oscillatory synchrony among peripheral receptors.
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Gamma-band synchronization coordinates brief periods of excitability in oscillating neuronal populations to optimize information transmission during sensation and cognition. Commonly, a stable, shared frequency over time is considered a condition for functional neural synchronization. Here, we demonstrate the opposite: instantaneous frequency modulations are critical to regulate phase relations and synchronization. In monkey visual area V1, nearby local populations driven by different visual stimulation showed different gamma frequencies. When similar enough, these frequencies continually attracted and repulsed each other, which enabled preferred phase relations to be maintained in periods of minimized frequency difference. Crucially, the precise dynamics of frequencies and phases across a wide range of stimulus conditions was predicted from a physics theory that describes how weakly coupled oscillators influence each other’s phase relations. Hence, the fundamental mathematical principle of synchronization through instantaneous frequency modulations applies to gamma in V1, and is likely generalizable to other brain regions and rhythms.
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Oscillation and noise filtration
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Dispersal in heterogeneous ecosystems, such as coastal metacommunities, is a major driver of diversity and productivity. According to theory, both species richness and spatial averaging shape a unimodal relationship of productivity with dispersal. We experimentally tested the hypothesis that disturbances acting on local patches would buffer the loss of productivity at high dispersal by preventing synchronized species oscillations. To simulate these disturbances, our experimental assemblages involved species that self-organized in isolation under three inflow pulsing frequencies, where hydraulic displacement and nutrient loading affected assemblage diversity and composition. At steady-state, the emerging isolated assemblages were connected at three levels of dispersal creating three metacommunities of different connectivity. Consistent with theory, as dispersal increased, species richness in the metacommunity declined; productivity however remained high. This occurred because the most productive species in our study (which dominated the isolated patch of intermediate inflow pulsing frequency) dominated all three patches (low, intermediate and high inflow pulsing frequencies) after dispersal commenced in our metacommunities. This experimental result provides empirical support for the mechanism of spatial averaging. Furthermore, disturbances, in the form of localized pulsed inflows, prevented population oscillation synchrony caused by homogenization. Overall, our observations suggest that localized environmental fluctuations and the identity of species seem to be more influential than dispersal in shaping the diversity and composition of phytoplankton assemblages and stabilizing productivity.
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transient rhythm / oscillation... beta rhythms / oscillations
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With shifts in island area, isolation, and cycles of island fusion-fission, the role of Quaternary sea-level oscillations as drivers of diversification is complex and not well understood. Here we conduct parallel comparisons of population and species divergence between two island areas of equivalent size that have been affected differently by sea-level oscillations, with the aim to understand the micro- and macroevolutionary dynamics associated with sea-level change. Using genome-wide datasets for a clade of seven Amphiacusta ground cricket species endemic to the Puerto Rico Bank (PRB), we found consistently deeper interspecific divergences and higher population differentiation across the unfragmented Western PRB, in comparison to the currently fragmented Eastern PRB that has experienced extreme changes in island area and connectivity during the Quaternary. We evaluate alternative hypotheses related to the microevolutionary processes (population splitting, extinction and merging) that regulate the frequency of completed speciation across the PRB. Our results suggest that under certain combinations of archipelago characteristics and taxon traits the repeated changes in island area and connectivity may create an opposite effect to the hypothesized “species pump” action of oscillating sea levels. Our study highlights how a microevolutionary perspective can complement current macroecological work on the Quaternary dynamics of island biodiversity.
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Datasets with results from all simulations of trajectories in 40 different conditions of oscillating optimum for d = 70.... Datasets with results from all simulations of trajectories in 40 different conditions of oscillating optimum for d = 40.... Dataset with the frequency of chaos at each simulation time point for different values of dimensionality (number of traits) d.
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Why did the London Millennium Bridge shake when there was a big enough crowd walking on it? What features of human walking dynamics when coupled to a shaky surface produce such shaking? Here, we use a simple biped model capable of walking stably in 3D to examine these questions. We simulate multiple such stable bipeds walking simultaneously on a bridge, showing that they naturally synchronize under certain conditions, but that synchronization is not required to shake the bridge. Under such shaking conditions, the simulated walkers increase their step-widths and expend more metabolic energy than when the bridge does not shake. We also find that such bipeds can walk stably on externally shaken treadmills, synchronizing with the treadmill motion for a range of oscillation amplitudes and frequencies, sometimes performing net positive work on the treadmill. Our simulations illustrate how interactions between (idealized) bipeds through the walking surface can produce emergent collective behavior that may not be exhibited by just a single biped.
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The code and data file provided to us by Janz et al. (2016) and used for their response. Note, that one will need to adjust the sampling frequencies to reflect accurate proportions of specialists and herbivores.
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