Building a Memory

Building a memory that is remembered forever requires that memory traces be transformed into a robust, stable form that is resistant to disruption. This process of strengthening memories is known as consolidation1.

An influential model of motor memory consolidation proposes that stabilization merely requires the passage of time after initial training, but offline gains require a sleep period soon after training2. A study by Korman et al.3 confirms that offline gains do indeed require sleep after training, but also finds that sleep promotes the stabilization of memories. Notably, these results suggest that processes of stabilization and memory enhancement interact, raising a number of questions about the conceptualization of motor memory consolidation and its dependency on sleep.

The findings of this study are a clear-cut demonstration that sleep enforces the stabilization of motor memories against interfering inputs. According to the previous model2, stabilization (resistance to interference) depends only on the passage of time, whereas performance enhancements depend on sleep.

Whatever the underlying mechanisms, this evidence that sleep-dependent stabilization and enhancement interact3 raises the question of whether memory stabilization during sleep and wakefulness are equivalent. In arguing that sleep 'condenses' the time course of motor memory consolidation, the authors imply that sleep after training merely accelerates a process of stabilization that would otherwise occur identically during wakefulness. However, this is not necessarily the case. Although behavioral performance indicates that eventually the same degree of stabilization of motor memories is obtained in both sleep and waking conditions, the underlying mechanisms may differ. Waking stabilization could result from synaptic consolidation (strengthening connections in the neural circuits that were activated during training), whereas sleep-dependent stabilization could result from system-level consolidation, in which representations are repeatedly reactivated and gradually redistributed to different networks and brain regions1. As reactivation and redistribution of memory representations interfere with ongoing sensorimotor processing, system consolidation is bound to an offline mode of processing that might be most effectively established by sleep4.


Source: One memory, two ways to consolidate? Nature, Neuroscience, Vol 10, No 9, Sept 2007


1) Dudai, Y. Annu. Rev. Psychol. 55, 51–86 (2004). | Article | PubMed | ISI |
2) Walker, M.P. Behav. Brain Sci. 28, 51–64 (2005). | Article | PubMed | ISI |
3) Korman, M. et al. Nat. Neurosci. 10, 1206–1213 (2007). | Article |
4) Born, J., Rasch, B. & Gais, S. Neuroscientist 12, 410–424 (2006). | PubMed | ISI |