Date of Award


Degree Type


Degree Name

Departmental Honors




The brain's ability to learn and remember is a topic of extensive debate and research. Mammals share many similarities, including the way in which information from the outside world is processed and stored. Mammalian circadian rhythms have long been thought to be essentially involved with these processes. Orexin, a neurotransmitter in the brain, plays a crucial role in arousal and circadian rhythm. This study is designed to explore the brain's ability to process and store information at different times of the circadian period, and to explore the role of orexin by comparing the performance of normal (wild-type) mice and abnormal (knockout) mice lacking a receptor for orexin in a spatial navigation task. Based on the results of previous research and the known roles of orexin in the brain, I predicted that wild-type mice that learn during the dark phase-which is their active phase-will perform better in a spatial learning and memory task than their counterparts that learn during the light phase, while knockout animals deficient in orexin receptor signaling will not be influenced by the diurnal timing of testing. I tested this prediction by comparing performance in a water-filled radial maze and by analyzing hypothalamic orexin neuron activation in animals tested at the beginning or at the end of their active period, using cFos immunohistochemistry. Our results point to a possible role of orexin in the diurnal variation of learning and memory.

Included in

Biology Commons



Faculty Mentor

Mona Buhusi

Departmental Honors Advisor

Scott Bates

Capstone Committee Member

Karen Kapheim