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Beyond the edge: Amplification and temporal integration by recurrent networks in the chaotic regime (Taro Toyoizumi)
发表时间:2011-11-29 阅读次数:1242次

Speaker: Taro Toyoizumi, Ph.D.

Time:     10:00 am, July 12 (Tuesday)

Venue:    Room 1704, East Guanghua Tower

Abstract:
 Randomly connected networks of neurons exhibit a transition from fixed-point to chaotic activity as the variance of their synaptic connection strengths is increased. In this study, we analytically evaluate how well a small external input can be reconstructed from a sparse linear readout of network activity.  At the transition point, known as the edge of chaos, networks display a number of desirable features, including large gains and integration times. Away from this edge, in the non-chaotic regime that has been the focus of most models and studies, gains and integration times fall off dramatically, which implies that parameters must be fine tuned with considerable precision if high performance is required. Here we show that, when the network units have an odd saturating nonlinear response function, the fall-off in gains and integration times is much slower on the chaotic side of the transition. Correspondingly, decoding performance is characterized, near the edge, by a critical exponent that takes a different value on the two sides. This means that, under appropriate conditions, good performance can be achieved with less fine tuning beyond the edge, within the chaotic regime.

Biography:
1. Education
  B.S. Department of Physics, Tokyo Institute of Technology, 2001
  M.S. Department of Complexity Science and Engineering, The University of Tokyo, 2003
  Ph.D. Department of Complexity Science and Engineering, The University of Tokyo, 2006

2. Positions
   Visiting researcher at W. Gerstner Lab (EPFL, Switzerland) from Dec 2003 to Nov 2004
   Visiting researcher at S. Amari Lab (RIKEN, Japan) from May 2005 to Feb 2008
  Postdoctoral research fellow at Center for Theoretical Neuroscience (Columbia   University, USA) from Sep 2006 
   to Mar 2010
   Special Postdoctoral Researcher at Brain Science Institute (RIKEN, Japan) from Apr 2010 to Mar 2011
   Laboratory Head, Brain Science Institute (RIKEN, Japan) from Apr 2011 to present.

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