The role of non-rapid eye movement slow-wave activity in prefrontal metabolism across young and middle-aged adults.

Electroencephalographic slow-wave activity (0.5-4 Hz) during non-rapid eye movement (NREM) sleep is a marker for cortical reorganization, particularly within the prefrontal cortex. Greater slow wave activity during sleep may promote greater waking prefrontal metabolic rate and, in turn, executive function. However, this process may be affected by age. Here we examined whether greater NREM slow wave activity was associated with higher prefrontal metabolism during wakefulness and whether this relationship interacted with age. Fifty-two participants aged 25-61 years were enrolled into studies that included polysomnography and a (18) [F]-fluoro-deoxy-glucose positron emission tomography scan during wakefulness. Absolute and relative measures of NREM slow wave activity were assessed. Semiquantitative and relative measures of cerebral metabolism were collected to assess whole brain and regional metabolism, focusing on two regions of interest: the dorsolateral prefrontal cortex and the orbitofrontal cortex. Greater relative slow wave activity was associated with greater dorsolateral prefrontal metabolism. Age and slow wave activity interacted significantly in predicting semiquantitative whole brain metabolism and outside regions of interest in the posterior cingulate, middle temporal gyrus and the medial frontal gyrus, such that greater slow-wave activity was associated with lower metabolism in the younger participants and greater metabolism in the older participants. These results suggest that slow-wave activity is associated with cerebral metabolism during wakefulness across the adult lifespan within regions important for executive function.