UC San Diego

Terrestrial organisms have evolved mechanisms to anticipate the environmental changes associated with diurnal variations in the environment. The primary such mechanism is the circadian timer which is a molecular clock present in every cell of mammals. In order to adjust to external variations, the circadian clock is plastic and responds to environmental stimuli. Two such stimuli are light and food timing. In this dissertation I describe two separate studies, one in mice and another in humans where we have attempted to characterize these two stimuli. In chapter 2, I describe a series of experiments performed in mice in which we have defined the extent of circadian and light driven transcription in the master clock, namely the suprachiasmatic nucleus, residing in the hypothalamic region of the brain. In chapter 3, I describe the development of a behavioral monitoring and data analysis system for understanding the extent of temporal spread of caloric intake in people. To our knowledge this is the first time that smartphones have been employed to characterize human behavior. Our data reveals previously unknown aspects of eating behaviors. In chapter 4, the results obtained from the human behavioral study are discussed. Lastly, in chapter 5, I mention our strategy for future studies using the approach described in chapter 3 and 4. Overall, this dissertation expands our knowledge of light and feeding time inputs to the mammalian timekeeping mechanisms