Charting epilepsy by searching for intelligence in network space with the help of evolving autonomous agents

J Physiol Paris. 2004 Jul-Nov;98(4-6):507-29. doi: 10.1016/j.jphysparis.2005.09.018. Epub 2005 Nov 14.

Abstract

The problem of demarcating neural network space is formidable. A simple fully connected recurrent network of five units (binary activations, synaptic weight resolution of 10) has 3.2 *10(26) possible initial states. The problem increases drastically with scaling. Here we consider three complementary approaches to help direct the exploration to distinguish epileptic from healthy networks. [1] First, we perform a gross mapping of the space of five-unit continuous recurrent networks using randomized weights and initial activations. The majority of weight patterns (>70%) were found to result in neural assemblies exhibiting periodic limit-cycle oscillatory behavior. [2] Next we examine the activation space of non-periodic networks demonstrating that the emergence of paroxysmal activity does not require changes in connectivity. [3] The next challenge is to focus the search of network space to identify networks with more complex dynamics. Here we rely on a major available indicator critical to clinical assessment but largely ignored by epilepsy modelers, namely: behavioral states. To this end, we connected the above network layout to an external robot in which interactive states were evolved. The first random generation showed a distribution in line with approach [1]. That is, the predominate phenotypes were fixed-point or oscillatory with seizure-like motor output. As evolution progressed the profile changed markedly. Within 20 generations the entire population was able to navigate a simple environment with all individuals exhibiting multiply-stable behaviors with no cases of default locked limit-cycle oscillatory motor behavior. The resultant population may thus afford us a view of the architectural principles demarcating healthy biological networks from the pathological. The approach has an advantage over other epilepsy modeling techniques in providing a way to clarify whether observed dynamics or suggested therapies are pointing to computational viability or dead space.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / physiology
  • Algorithms
  • Animals
  • Biological Clocks / physiology
  • Brain Mapping / methods*
  • Computer Simulation*
  • Epilepsy / physiopathology*
  • Epilepsy / therapy
  • Humans
  • Mathematics
  • Models, Neurological*
  • Motor Neurons / physiology
  • Nerve Net / physiopathology*
  • Neural Networks, Computer
  • Neuronal Plasticity / physiology
  • Robotics