Neural Mechanisms for Generating Temporal Coding

Bose 9973230 The goal of this project is to develop biophysical models and the accompanying mathematical techniques to describe the generation of temporal codes by the activity patterns of networks of neurons. The investigators focus on a robust temporal code, called phase precession, that has been experimentally found in the firing pattern of pyramidal cells in the hippocampus of freely moving rats. This temporal code is believed to signal the animal's location in a known environment. The investigators apply a modeling approach consisting of three complementary methods: mathematical analysis of networks of simplified neurons, simulations of networks of biophysical neurons, and functional modeling that incorporates and interprets experimental recordings from freely moving rats. The mathematical approach, using geometric singular perturbation theory, exploits the multiple time scales inherent in the intrinsic descriptions of the cells and the synapses between these cells. Simulations are performed on networks of conductance based neurons. Genetic algorithms, previously developed by the researchers, and bifurcation continuation programs aid in analyzing the simulation results. A goal of the analysis and simulations is to make experimentally verifiable predictions. The hippocampus is a primary target for epilepsy and Alzheimer's Disease and has a well established role in memory function and in spatial navigation abilities. The dynamical interaction between neurons in the hippocampus may be described using temporal coding schemes. In order to detect potentially pathological dynamics of these neurons, it is essential to first understand how these coding schemes are constructed under normal circumstances. More generally, a fundamental goal of neuroscience is to understand function from the single neuron level to the systems level. The objective of this project is to bridge all of the levels of detail for one specific system, the hippocampus. This work will also lay the mathematical foundation for research in other areas of the brain where temporal codes exist. Funding for the project is provided by the program of Computational Mathematics and the Office of Multidisciplinary Activities in MPS and by the Computational Neuroscience program in BIO.