1999 Jun 29 (Tue), 10:30 AM
羅 昭 容 教授
UNIversity of Maryland
Sodium channels are voltage-sensitive protein pores located in the cell
membrane of nerves and other tissues. They play a central role in the
generation of nerve impulses. The understanding of how an impulse is
generated and the functions of ion channels was greatly enhanced by the
invention of the patch-clamp technique by Neher and Sakman (1976). They
were awarded the Nobel Prize in Physiology and Medicine in 1991. The
technique allows recording, at the single channel level, of microscopic
currents that flow through these channels. For such data, absorbing
Markov chains have been widely used as models for studying the behavior
of sodium channels; especially the "gating" behavior of channels.
Among many statistical problems that arise in the channel studies, we
discuss model identification and parameter estimation; and present some
of our results. We use strong unimodality as a criterion for model
identification. The problem of parameter estimation is complex due to the
fact that the experimental data are only partially observable and mixed.
The distribution of the data is a mixture of several absorbing Markov
chains with hidden states. We use Le Cam's asymptotic procedure to
estimate parameters and illustrate the results with experimental data.