Memory consolidation in human sleep depends on inhibition of glucocorticoid release

EARLY sleep dominated by slow-wave sleep has been found to be particularly relevant for declarative memory formation via hippocampo-neocortical networ ks. Concurrently, early nocturnal sleep is characterized by an inhibition o f glucocorticoid release from the adrenals. Here, we show in healthy humans that this inhibition serves to support declarative memory consolidation du ring sleep. Elevating plasma glucocorticoid concentration during early slee p by administration of cortisol impaired consolidation of paired associate words, but not of non-declarative memory of visuomotor skills. Since glucoc orticoid concentration was enhanced only during retention sleep, but not du ring acquisition or retrieval, a specific effect on the consolidation proce ss is indicated. Blocking mineralocorticoid receptors by canrenoate did not affect memory, suggesting inactivation of glucocorticoid receptors to be t he essential prerequisite for memory consolidation during early sleep. (C) 1999 Lippincott Williams & Wilkins.