1994 Special Issue: A biologically based model of functional properties of the hippocampus

  • Authors:

  • Theodore W. Berger;Gilbert Chauvet;Robert J. Sclabassi

  • Affiliations:

  • Department of Biomedical Engineering, University of Southern California, USA and Program in Neuroscience, University of Southern California, USA;Department of Biomedical Engineering, University of Southern California, USA and Institute for Theoretical Biology, University of Angers, France;Departments of Neurological Surgery and Electrical Engineering, University of Pittsburgh, USA

  • Venue:
  • Neural Networks - Special issue: models of neurodynamics and behavior
  • Year:
  • 1994

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Abstract

The hippocampus is a brain structure essential for learning and memory processes, although its precise role has yet to be determined despite intensive experimental study. A combined experimental/theoretical approach is outlined for realizing a biologically based representation of the hippocampal formation. The approach involves developing two models, one a ''nonparametric'' model in which the subsystems, principal neurons, and subcellular processes of the principal neurons are characterized experimentally using random impulse train stimulation. Nonlinearities in the input/output relation are represented as the kernels of a functional power series. Using multidimensional z-transforms, a procedure is demonstrated for deriving kernel functions for interneurons that are not directly observable. A scheme is proposed for developing an ''external'' model of the hippocampus, in which the system is represented as the composite of the input/output functions of its intrinsic elements. The second model is an ''internal'' model, derived from an n-level field theory, in which specific cellular and subcellular processes are included as the parameters of coupled field equations describing the dynamics at a different hierarchical levels of nervous system function. The current model consists of two field equations for each of the synaptic and neuronal levels, respectively; included in each are geometrical relations to incorporate anatomical characteristics (e.g., connectivity patterns, synaptic, and cell densities) of the system. It is proposed that the two models be used in a complementary manner to achieve an understanding of the neurobiological basis of the system dynamics, and thus the mnemonic function, of the hippocampus.