Regional Rates of Cerebral Protein Synthesis: Effects of Sleep and Memory Consolidation

The importance of sleep is widely appreciated, but the actual function of sleep remains unknown. Sleep occurs in much of the animal kingdom, in all mammals and birds and even in some lower forms. Sleep deprivation impairs brain function, and in rats, total sleep deprivation for 2-3 weeks results in death. One hypothesized role of sleep is for restoration and reorganization of neuronal circuits. There is some indirect evidence that during sleep, when cerebral energy requirements are reduced, cell resources are diverted to protein synthesis for the restoration of structure and function. The objectives of the present study are: 1) to further define the relationship between regional rates of cerebral protein synthesis (rCPS) and sleep and 2) to ascertain whether sleep-dependent visual learning during slow wave sleep (SWS) results in increases in rCPS in the primary visual cortex. We propose to use a novel positron emission tomography (PET)-based technique to quantify regional rates of cerebral protein synthesis (rCPS) in young, adult, healthy volunteers. The first objective will be addressed in Part I in which we will study each subject under the following three conditions: 1) awake and sleep-sated, 2) awake and sleep-deprived, and 3) during SWS after sleep-deprivation. Our aim is to complete fully successful studies in 15 subjects. The second objective will be addressed in Part II in which we will assess the relationship between rCPS and sleep-dependent visual learning on a retinotopically specific task. Each participant will serve as his own control by comparing the trained primary visual cortex hemisphere with the untrained hemisphere to which comparable visual information is presented but without learning. In Part II we will study two groups of subjects: 1) One group will be studied during SWS following the training session; 2) The second group will be studied at the same interval following the training session but awake. Subjects will be monitored with polysomnography to identify the stages of sleep. Our aim in part II is to complete fully successful studies in 15 subjects in each of the two groups. We anticipate that the results of Part I will identify changes in rCPS in specific brain regions which are characteristic of SWS and results of Part II may reveal relationships between rCPS and memory consolidation during SWS.