A Brief Description of Two Potential
Workshops
Dr. Charles Stevens
The Salk Institute for Biological Studies
10010 North Torrey Pines Road
La Jolla, CA 92037
(619) 453-4100
A variety of problems in neurobiology are naturally described in terms of complex adaptive systems; two examples are given here.
Because of the enormous complexity of neural networks a microliter of cortex contains a billion connections between nerve cells and 4 km of wires the arrangement of the circuit components is critical. Each neuron must follow a set of local rules and interact with neighbors during development to generate the correct pattern of neuronal positions and interconnections. This type of problem can be treated on several levels: one can try to model the entire developmental process, or one can use a higher level optimality principle to understand how the patterns form. In either case, the methods of condensed matter physics certainly provide the appropriate theoretical framework. Possible workshop: pattern formation and cortical architecture.
In classical investigations of brain function the scientist studied the behavior one neuron at a time and made the tacit assumption that correlations between the behavior of neurons are trivial, that is, just arise from the fact that a population is neurons is representing the same time varying signal. With improved technology, it is now possible to study tens or hundreds neurons simultaneously. The unexpected discovery has been that the firing of neurons is highly correlated and it appears that the correlations are important for the representation of information. For example, the average rate at which neurons in auditory cortex produce nerve impulses sometimes does not change when sounds are presented, but the discharge of neurons becomes correlated where it was not before. How the synchronization of firing arises, and how it is used in neural computation are important outstanding problems in neurobiology; again, condensed matter physics provides the appropriate theoretical framework. Possible workshop: Mechanism and significance of synchronized neuronal discharges.