Doctor of Philosophy (Ph.D.), Bowling Green State University, 2006, Psychology/Experimental

Many typically diurnal songbirds experience dramatic sleep loss during the migratory seasons because of their nocturnal flights. However, nocturnally migrating songbirds continue to function normally with no observable effect of sleep loss on their behavior. To mitigate the effects of sleep loss, nocturnal migrants may engage in daytime sleep, unihemispheric sleep, sleep during migratory flight, or increased quality of what sleep is available. Studying the Swainson's thrush, a long-distance trans-gulf migrant, I investigated how avian migrants might compensate for sleep loss during the migratory season. Daytime behavior, nighttime behavior and forebrain EEG activity was recorded in thrushes when migratory and non-migratory. Behavioral sleeping postures and their EEG/brain correlates were identified throughout the 24 h light-dark cycle. Slow wave sleep (SWS) and rapid eye movement (REM) sleep were investigated, and the temporal profile of the two sleep states was analyzed. Brain activity (EEG power) in the delta frequency band (1.5 – 4Hz) was employed as a measure of sleep quality. Interestingly, the most prominent alterations in sleep and sleep-related behavior in nocturnally active migratory thrushes were found during the day. In contrast to their behavior when non-migratory, migratory Swainson's thrushes engaged in numerous episodes of daytime sleep, unilateral eye closure, and an intermediate sleep-like state referred to as drowsiness. The electrophysiological recordings demonstrated that the observed behavior was accompanied by reliable sleep like changes in brain activity. In addition, EEG activity during episodes of unilateral eye closure was frequently accompanied byinterhemispheric asymmetries characteristic of unihemispheric sleep. The relatively brief but frequent daytime sleep states (“micro naps”) may represent an adaptive balance that enables migratory birds to compensate for extended periods of nocturnal sleep loss during the subsequent day without ren (open full item for complete abstract)

Committee: Verner Bingman (Advisor) Subjects: Biology, Neuroscience