Mathematical Biology Seminar Cecilia Behn, Harvard Univesity Wednesday Jan. 31, 2007 2:55pm in LCB 219 "Networks, nullclines, and narcolepsy: investigating dynamics of mouse sleep-wake behavior " Abstract: Behavioral states of wake, rapid eye movement (REM) sleep, and non-REM (NREM) sleep and the transitions among them are regulated by a network of neurons in the brainstem and hypothalamus. We developed a mathematical model of this sleep-wake network using coupled relaxation oscillators. This model simulates realistic mouse sleep-wake behavior on several time scales. In appropriate low-dimensional subspaces, geometric analysis of model dynamics predicts mechanisms for transitions among behavioral states and suggests a basis for the observed qualitative difference between brief and sustained wake bouts. In current work, we are investigating properties of network circuitry and mechanisms associated with normal (e.g., circadian promotion of arousal) and pathologic (e.g., loss of orexin neurons in narcolepsy) modulation of baseline network dynamics.