Electronic Theses and Dissertations

Identifier

190

Date

2010

Date of Award

12-1-2010

Document Type

Thesis

Degree Name

Master of Science

Major

Physics

Concentration

General Physics

Committee Chair

Mark C. Ospeck

Committee Member

David A. Freeman

Committee Member

Mohamed Laradji

Abstract

The suprachiasmatic nuclei (SCN), the principal mammalian circadian oscillator, contain several thousand clock neurons that oscillate spontaneously with ~24-hour periods in its ventrolateral region. Without light, this network synchronizes through action potentials releasing VIP, compromising on a free-running period near 24 hours. We entrained Siberian hamsters to various light-dark cycles and tracked their activity into constant darkness showing that they retain memory for a particular light-dark cycle to which they were entrained before returning to their own free-running period. Using Leloup-Goldbeter mammalian clock neurons, we model the ventrolateral SCN network and show that light acting weakly upon a strongly rhythmic VIP oscillation can explain the light-dark cycle memory that we observe. Additionally, light is known to initiate a MAP kinase signaling cascade that induces transcription of both per and mpk1 phosphatase. We show that the ensuing phosphatase-kinase interaction can account for the dead zone in the mammalian phase response curve.

Comments

Data is provided by the student.

Library Comment

dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.

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