Behavioral, neurophysiological and evolutionary perspectives on unihemispheric sleep

Rattenborg, Niels Christian; Amlaner, Charles J.; Lima, Steven L.

doi:10.1016/s0149-7634(00)00039-7

Cited by 488 publications

(345 citation statements)

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“…In particular, Hindmarsh-Rose neural oscillators have been studied in networks with nonlocal [15] and nearestneighbor [16] coupling, as well as in modular networks consisting of communities [17]. Potential relevance of chimera states in this context include bump states [18,19] and the phenomenon of unihemispheric sleep observed in birds and dolphins [20], which sleep with one eye open, meaning that half of the brain is synchronous with the other half being asynchronous. Furthermore, it has been recently hypothesized that chimera states are the route of onset or termination of epileptic seizures [21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Chimera patterns in two-dimensional networks of coupled neurons

et al. 2017

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We discuss synchronization patterns in networks of FitzHugh-Nagumo and Leaky Integrate-andFire oscillators coupled in a two-dimensional toroidal geometry. Common feature between the two models is the presence of fast and slow dynamics, a typical characteristic of neurons. Earlier studies have demonstrated that both models when coupled nonlocally in one-dimensional ring networks produce chimera states for a large range of parameter values. In this study, we give evidence of a plethora of two-dimensional chimera patterns of various shapes including spots, rings, stripes, and grids, observed in both models, as well as additional patterns found mainly in the FitzHughNagumo system. Both systems exhibit multistability: For the same parameter values, different initial conditions give rise to different dynamical states. Transitions occur between various patterns when the parameters (coupling range, coupling strength, refractory period, and coupling phase) are varied. Many patterns observe in the two models follow similar rules. For example the diameter of the rings grows linearly with the coupling radius.

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Section: Introductionmentioning

confidence: 99%

Chimera patterns in two-dimensional networks of coupled neurons

et al. 2017

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“…Many creatures sleep with only half their brain at a time [1]. Such unihemispheric sleep was first reported in dolphins and other sea mammals, and has now been seen in birds and inferred in lizards [2].…”

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confidence: 99%

Solvable Model for Chimera States of Coupled Oscillators

et al. 2008

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Networks of identical, symmetrically coupled oscillators can spontaneously split into synchronized and desynchronized sub-populations. Such chimera states were discovered in 2002, but are not well understood theoretically. Here we obtain the first exact results about the stability, dynamics, and bifurcations of chimera states by analyzing a minimal model consisting of two interacting populations of oscillators. Along with a completely synchronous state, the system displays stable chimeras, breathing chimeras, and saddle-node, Hopf and homoclinic bifurcations of chimeras. [2]. When brain waves are recorded, the awake side of the brain shows desynchronized electrical activity, corresponding to millions of neurons oscillating out of phase, whereas the sleeping side is highly synchronized.From a physicist's perspective, unihemispheric sleep suggests the following (admittedly, extremely idealized) problem: What's the simplest system of two oscillator populations, loosely analogous to the two hemispheres, such that one synchronizes while the other does not?Our work in this direction was motivated by a series of recent findings in nonlinear dynamics [3,4,5,6,7,8]. In 2002, Kuramoto and Battogtokh reported that arrays of nonlocally coupled oscillators could spontaneously split into synchronized and desynchronized subpopulations [3]. The existence of such "chimera states" came as a surprise, given that the oscillators were identical and symmetrically coupled. On a one-dimensional ring [3,4] the chimera took the form of synchronized domain next to a desynchronized one. In two dimensions, it appeared as a strange new kind of spiral wave [5], with phase-locked oscillators in its arms coexisting with phaserandomized oscillators in its core-a circumstance made possible only by the nonlocality of the coupling. These phenomena were unprecedented in studies of pattern formation [9] and synchronization [10] in physics, chemistry, and biology, and remain poorly understood.Previous mathematical studies of chimera states have assumed that they are statistically stationary [3,4,5,6,7]. What has been lacking is an analysis of their dynamics, stability, and bifurcations.In this Letter we obtain the first such results by considering the simplest model that supports chimera states: a pair of oscillator populations in which each oscillator is coupled equally to all the others in its group, and less strongly to those in the other group. For this model we solve for the stationary chimeras and delineate where they exist in parameter space. An unexpected finding is that chimeras need not be stationary. They can breathe. Then the phase coherence in the desynchronized population waxes and wanes, while the phase difference between the two populations begins to wobble.The governing equations for the model arewhere σ = 1, 2 and N σ is the number of oscillators in population σ. The oscillators are assumed identical, so the frequency ω and phase lag α are the same for all of them. The strength of the coupling from oscillators in σ ′ onto those in σ...

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“…These data support the idea that sleep is to some extent a local phenomenon (Krueger and Obal, 1993;Krueger et al, 1999;Tobler, 2005). The EEG asymmetry in marine mammals (cetaceans and pinnipeds) and in some birds (Rattenborg et al, 2000) is associated with asymmetrical eye state as well as with lateralized paddle activity in fur seals. This asymmetry results from a major difference in the amplitude and timing of EEG changes of the two cortical hemispheres, whereas the much smaller EEG asymmetry that has been reported in rats and humans is probably "use-dependent" in nature, being a consequence of more extensive activity of some brain tissue during the previous waking period (Kattler et al, 1994;Huber et al, 2004;Vyazovskiy and Tobler, 2008).…”

Section: Discussionmentioning

confidence: 99%