Abstract
This review is dedicated to the role of cortisol in behavior and sleep grounded on evidence-based information that acute and chronic stress (in particular the stress-induced release of glucocorticoids), induce changes in glutamate neurotransmission in prefrontal cortex and hippocampus, and infl uence cognitive processing. Dysfunction of glutamatergic neurotransmission is indeed more considered pivotal in stress-related neuropsychiatric disorders. Sleep is important for memory consolidation. Recently new data has shown the multifaceted nature of sleep-related motor memory consolidation. Intriguingly, motor learning does not alone take place during the actual task but also between training sessions including periods of sleep. Knowing that sleep may increase performance of motor tasks in subsequent retests, an effect specifi c to the sleep towards the end of the sleep cycle, when receptor occupancies will change. That cortisol profi les show individual diurnal rhythms warrants further appreciation of the pivotal role of cortisol in sleepwake physiology and behavioural performance. It is safe to conclude that cortisol is a hormone during wake and during sleep.