Character from statistical relationship among node studies, amplitude from regional vibrations and you can directionality of relationships

Character from statistical relationship among node studies, amplitude from regional vibrations and you can directionality of relationships

After that, the latest directionality between all of the regional node personality are mentioned by using the directed stage lag directory (dPLI), and this exercises the fresh stage direct and slowdown relationships anywhere between a couple of oscillators (look for Materials and methods getting detail by detail meaning)

This new central intent behind this study were to pick an over-all relationships of community topology, regional node fictional character and you can directionality within the inhomogeneous networks. We continued by building a straightforward paired oscillatory circle design, having fun with a great Stuart-Landau model oscillator to help you show this new sensory mass inhabitants craft from the each node of one’s network (discover Information and methods, and you may S1 Text to have details). The latest Stuart-Landau model is the normal style of the newest Hopf bifurcation, for example it’s the greatest design capturing the quintessential top features of the system near the bifurcation section [22–25]. The fresh Hopf bifurcation appears generally into the physical and you may chemical compounds expertise [24–33] which can be commonly accustomed investigation oscillatory choices and you will head dynamics [twenty-five, 27, 31, 33–36].

I basic ran 78 combined Stuart-Landau designs on a level-100 % free design community [37, 38]-that’s, a network having a diploma shipping following an electrical energy laws-where coupling stamina S ranging from nodes can be varied as handle factor. New sheer regularity of each node are at random drawn away from a good Gaussian shipping to the indicate during the 10 Hz and you will important departure of just one Hz, simulating the fresh alpha bandwidth (8-13Hz) away from human EEG, and we also systematically ranged the fresh new coupling stamina S out of 0 to help you 50. We plus varied the time slow down parameter across the a general assortment (2

50ms), but this did not yield a qualitative difference in the simulation results as long as the delay was less than a quarter cycle (< 25 ms) of the given natural frequency (in this case, one cycle is about 100 ms since the frequency is around 10Hz). The simulation was run 1000 times for each parameter set.

We after that went on to spot the fresh relationship between system topology (node studies), node character (amplitude) and directionality between node fictional character (dPLI) (see S1 Text message having complete derivation)

dPLI between two nodes a and b, dPLIab, can be interpreted as the time average of the sign of phase difference . It will yield a positive/negative value if a is phase leading/lagging b, respectively. dPLI was used as a surrogate measure for directionality between coupled oscillators . Without any initial bias, if one node leads/lags in phase and therefore has a higher/lower dPLI value than another node, the biased phases reflect the directionality of interaction of coupled local dynamics. dPLI was chosen as the measure of analysis because its simplicity facilitated the analytic derivation of the relationship between topology and directionality. However, we note that we also reach qualitatively similar conclusions with our analysis of other frequently-used measures such as Granger causality (GC) and symbolic transfer entropy (STE) (see S1 Text and S1 Fig for the comparison) [39–41].

Fig 2A–2C demonstrates how the network topology is related to the amplitude and phase of local oscillators. Fig 2A shows the mean phase coherence (measure of how synchronized the oscillators are; see Materials and Methods for details) for two groups of nodes in the network: 1) hub nodes, here defined as nodes with a degree above the group standard deviation (green triangles, 8 out of 78 nodes); and 2) peripheral nodes, here defined as nodes with a degree of 1 (yellow circles, 33 out of 78 nodes). When the coupling strength S is large enough, we observed distinct patterns for each group. For example, at the coupling strength of S = 1.5, which represents a state in between the extremes of a fully desynchronized and a fully synchronized network (with the coherence value in the vicinity of 0.5), the amplitudes of node activity are plitudes, and peripheral nodes, with smaller amplitudes (Fig 2B). More strikingly, the phase lead/lag relationship is clearly differentiated between the hub and peripheral nodes: hub nodes phase lag with dPLI 0 (Fig 2C). Fig 3 shows the simulation results in random and scale-free networks, which represent two extreme cases of inhomogeneous degree networks. This figure clearly demonstrates that larger degree nodes lag in phase with dPLI <0 and larger amplitude (see S2 Fig for various types of networks: scale free, random, hierarchical modular and two different human brain networks) even at the coupling strength S = 1.5, where the separation of activities between hub nodes and peripheral nodes just begins to emerge. To explain these simulation results, we utilized Ko et al.'s mean-field technique approach to derive the relationships for the coupled Stuart-Landau oscillators with inhomogeneous coupling strength, which in turn can be applied to inhomogeneous degree networks by interpreting inhomogeneous coupling strength as inhomogeneous degree for each oscillator .

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