36,198 research outputs found
Complexity without chaos: Plasticity within random recurrent networks generates robust timing and motor control
It is widely accepted that the complex dynamics characteristic of recurrent
neural circuits contributes in a fundamental manner to brain function. Progress
has been slow in understanding and exploiting the computational power of
recurrent dynamics for two main reasons: nonlinear recurrent networks often
exhibit chaotic behavior and most known learning rules do not work in robust
fashion in recurrent networks. Here we address both these problems by
demonstrating how random recurrent networks (RRN) that initially exhibit
chaotic dynamics can be tuned through a supervised learning rule to generate
locally stable neural patterns of activity that are both complex and robust to
noise. The outcome is a novel neural network regime that exhibits both
transiently stable and chaotic trajectories. We further show that the recurrent
learning rule dramatically increases the ability of RRNs to generate complex
spatiotemporal motor patterns, and accounts for recent experimental data
showing a decrease in neural variability in response to stimulus onset
Analysis of attractor distances in Random Boolean Networks
We study the properties of the distance between attractors in Random Boolean
Networks, a prominent model of genetic regulatory networks. We define three
distance measures, upon which attractor distance matrices are constructed and
their main statistic parameters are computed. The experimental analysis shows
that ordered networks have a very clustered set of attractors, while chaotic
networks' attractors are scattered; critical networks show, instead, a pattern
with characteristics of both ordered and chaotic networks.Comment: 9 pages, 6 figures. Presented at WIRN 2010 - Italian workshop on
neural networks, May 2010. To appear in a volume published by IOS Pres
Chaos and Asymptotical Stability in Discrete-time Neural Networks
This paper aims to theoretically prove by applying Marotto's Theorem that
both transiently chaotic neural networks (TCNN) and discrete-time recurrent
neural networks (DRNN) have chaotic structure. A significant property of TCNN
and DRNN is that they have only one fixed point, when absolute values of the
self-feedback connection weights in TCNN and the difference time in DRNN are
sufficiently large. We show that this unique fixed point can actually evolve
into a snap-back repeller which generates chaotic structure, if several
conditions are satisfied. On the other hand, by using the Lyapunov functions,
we also derive sufficient conditions on asymptotical stability for symmetrical
versions of both TCNN and DRNN, under which TCNN and DRNN asymptotically
converge to a fixed point. Furthermore, generic bifurcations are also
considered in this paper. Since both of TCNN and DRNN are not special but
simple and general, the obtained theoretical results hold for a wide class of
discrete-time neural networks. To demonstrate the theoretical results of this
paper better, several numerical simulations are provided as illustrating
examples.Comment: This paper will be published in Physica D. Figures should be
requested to the first autho
Chaotic Iterations for Steganography - Stego-security and chaos-security
International audienceChaotic neural networks have received a great deal of attention these last years. In this paper we establish a precise correspondence between the so-called chaotic iterations and a particular class of artificial neural networks: global recurrent multi-layer perceptrons. We show formally that it is possible to make these iterations behave chaotically, as defined by Devaney, and thus we obtain the first neural networks proven chaotic. Several neural networks with different architectures are trained to exhibit a chaotical behavior
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