A group of about 20,000 neurons in the hypothalamus, the SCN receives information about the light/dark cycle from the external world through the retina that can affect the circadian process. "The job of this part of brain is to know what time of day it is," Diekman says succinctly. It is a job that the SCN also may do without direct exposure to external light/dark conditions.
Two Vastly Different Time Scales
At the neuronal level, the interplay of several ionic currents within SCN neurons produces electrical oscillations on the time scale of milliseconds. Ultimately, these electrical signals add up to our daily behavior patterns. Experimentally, the challenge has been to collect data about these currents under precisely controlled light/dark conditions in order to study how SCN activity may vary over a particular period, such as 24 hours. While collecting this data is a very labor-intensive process, it provides the raw material for Diekman's mathematical modeling.
A key goal of the resulting model is to integrate the experimental data into a comprehensive physiological portrait to simulate neuronal activity and clarify the discrete roles of various ionic currents, Diekman explains. And a major mathematical objective is to take information about biological events that occur on a millisecond time scale and determine how they collectively affect 24-hour behavioral patterns. The model can then be used to make predictions about the circadian time-keeping process that can be verified in the laboratory, and to suggest new experiments that will add to our knowledge in this area.
"We want to understand the interaction between two different biologi
|Contact: Tanya Klein|
New Jersey Institute of Technology