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.