The influence of age on the neurophysiologic and neurobehavioral response to sleep deprivation and subsequent recoveryPublic Deposited
Sleep deprivation (Sd) preferentially impairs predictive and adaptive behaviors that shift responses based on the appropriate context. Behavioral studies implicate the frontal lobes as particularly susceptible to Sd. Aging also impairs frontal functioning, and alters the response to Sd. The interaction between age and Sd is poorly understood, and few studies have examined the underlying neurophysiology of this interaction. This dissertation investigates the effects of Sd on neural responses, as measured by functional magnetic resonance imaging (fMRI), associated with endogenously cued attention shifting and inhibitory control. The first study examines how Sd affects the ability to utilize predictive cues, and the second study examines the effects of Sd, age, and their interaction on brain function. Recovery from Sd is poorly understood, so the second study also examines recovery of performance and related brain activation. Recovery from Sd should be related to recovery sleep physiology, and age impacts sleep physiology. Thus, relationships between sleep physiology and daytime brain function are explored. In study one; Sd alters how posterior cingulate and parietal activations are associated with faster attention shifts. This alteration is associated with a general change in behavioral performance in which predictive cues no longer provide a response time benefit. This suggests a change in cognitive strategy from one that utilizes cues to predict target location to one that reacts to target appearance. In study two; we show that Sd alters how brain activation leads to successful inhibitory performance. How this functional reorganization manifests is dependent upon how tasks are performed at baseline, which is affected by age. Further, the neural response to Sd and subsequent recovery sleep is also age-dependent, and how sleep recovers next day brain activation is altered in old adults. These age-related changes in the neural response to Sd and recovery do not necessarily result in worse performance outcomes. However, future attempts to better understand, predict, and manage the effects of Sd or improve the effects of recovery sleep on daytime function will need to account for age. This is because age alters how the brain resists and recovers from sleep deprivation.