Office of the President

UNDERSTANDING NEURAL NETWORKS

Amithaba Bose

New insights into short-term synaptic plasticity (STSP) -- the ability of a synapse to change in strength based on how it is being used -- is the goal of Amitabha Bose, PhD, associate professor of mathematical sciences. With NSF funding, he is developing mathematical models to chart the neuron patterns in the crustacean digestive system and in the rat hippocampus, the region of the brain believed to control spatial memory in animals. The goal is to derive a general understanding of how STSP works.

He had also looked at  ways that the activity patterns of networks of neurons convey information. In particular, in region CA3 of the rat hippocampus, place cells fire when an animal is in a spatially specific known environment.  Experiments have shown that when the animal is running through what is known as the place field of the cell, the phase of the place cell firing systematiclally precesses through up to 360 degrees with respect to the background EEG rhythm. Alternatively, when an animal is running , but fixed in space as in a running wheel, then the phase of firing is fixed. The voltage traces below show results from a minimal, biophysically realistic model of the CA3 region of the hippocampus.

The first set of traces shows the phase precession of place cells within the place field, while the second shows the phase locking of cells.  In both traces, P represents the place cell, I represents an interneuron and T is the background EEG. The results below suggest that the animal uses the phase of firing as mechanism to determine its location in space.