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A neural network model for explaining experimentally observed neuronal responses in cat primary visual cortex is proposed. In our model, the basic functional unit is an orientation column which is represented by a large homogeneous population of neurons modeled as integrate-and-fire type excitable elements. The orientation column exhibits spontaneous… (More)
We consider the effect of microscopic external noise on the collective motion of a globally coupled map in fully desynchronized states. Without the external noise a macroscopic variable shows high-dimensional chaos distinguishable from random motions. With the increase of external noise intensity, the collective motion is successively simplified. The number… (More)
We study a generalization of globally coupled maps, where the elements are updated with probability p. When p is below a threshold p(c), the collective motion vanishes and the system is the stationary state in the large size limit. We present the linear stability analysis.
Population dynamics in random ecological networks are investigated by analyzing a simple deterministic equation. It is found that a sequence of abrupt changes of populations punctuating quiescent states characterize the long time behavior. An asymptotic analysis is developed by introducing a log-scaled time, and it is shown that such a dynamical process… (More)
The characteristics of long lasting but not perpetual chaotic states appear in a wide parameter region in a globally coupled overcritical tent map system are exhibited. The lifetime of the transient state has essential relevance with the system size. In some parameter region, the lifetime saturates at a certain level, while in another region it seems to… (More)