Dissociable stages of human memory consolidation and reconsolidation

Historically, the term 'memory consolidation' refers to a process whereby a memory becomes increasingly resistant to interference from competing or disrupting factors with the continued passage of time(1). Recent findings regarding the learning of skilled sensory and motor tasks ('procedural learning') have refined this definition, suggesting that consolidation can be more strictly determined by time spent in specific brain states such as wake, sleep or certain stages of sleep(2-8). There is also renewed interest(9) in the possibility that recalling or 'reactivating' a previously consolidated memory renders it once again fragile and susceptible to interference(10-12), therefore requiring periods of reconsolidation(13-15). Using a motor skill finger-tapping task, here we provide evidence for at least three different stages of human motor memory processing after initial acquisition. We describe the unique contributions of wake and sleep in the development of different forms of consolidation, and show that waking reactivation can turn a previously consolidated memory back into a labile state requiring subsequent reconsolidation.