Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Editorial
. 2009 Oct;13(5):305-8.
doi: 10.1016/j.smrv.2009.05.004. Epub 2009 Aug 21.

How do I remember? Let me count the ways

Robert Stickgold
Editorial

How do I remember? Let me count the ways

Robert Stickgold. Sleep Med Rev. 2009 Oct.
No abstract available

PubMed Disclaimer

Figures

Figure 1
Figure 1. The sleep cycle, memory systems, and memory stages
(A) The human sleep cycle—across the night, NREM and REM sleep cycle every 90 min in an ultradian manner, while the ratio of NREM to REM sleep shifts. During the first half of the night, stages 3 and 4 NREM (SWS) dominate, while stage 2 NREM and REM sleep prevail in the latter half of the night. EEG patterns also differ significantly between sleep stages, with electrical oscillations such as K complexes and sleep spindles occurring during stage 2 NREM, slow (0.5–4Hz) delta waves developing in SWS, and theta waves seen during REM. (B) Memory systems—human memory is most commonly divided into declarative forms, with further subdivisions into episodic and semantic; and nondeclarative forms, subdivided into an array of different types including procedural skill memory (C) Developing stages of memory—following the initial encoding of a memory, several ensuing stages are proposed, beginning with consolidation, as well as integration of the memory representation, translocation of the representation, or erasure of the memory. Also, following later recall, the memory representation is believed to become unstable once again, requiring periods of reconsolidation. Reproduced from .
Figure 2
Figure 2. Time course of memory processes
(a) Memory formation and consolidation. After the initial rapid encoding of a sensory experience, the neural representation of the memory can go through several automatic processes, independent of rehearsal, intent or awareness. These can stabilize and enhance a memory, so it is resistant to interference and more effective to guiding behavior, and can also integrate the memory into larger associative networks. The latter process is thought to permit episodic memories to be recalled without hippocampal (HC) involvement. The extent to which such processes affect different memory systems is unclear. Note the logarithmic time scale. (b) Memory reactivation and reconsolidation (featuring an enlargement of (a), as indicated by the gray shading). After stabilization is complete, reactivation of a memory can lead to its return to an unstable form. Normally, such memories appear to be reconsolidated following this destabilization but, if such reconsolidation is blocked, degradation of the memory can ensue (see also Figure 4). Solid bars represent periods of known processing; dotted bars reflect hypothesized or variable periods of processing. Reproduced from .
Figure 3
Figure 3. Time-dependent and sleep-dependent improvement on serial reaction time task
Subjects trained at either 8AM (Wake) or 8PM (Sleep) and were retested 12hr later. Top: Hippcampally dependent learning – subjects were informed of the presence of the repeating response sequence prior to training; Bottom: Non-hippocampally mediated learning – subjects were not informed of the sequence, and did not become aware of it during training. Modified from .
Figure 4
Figure 4. Logistic curve for memory strength
The extent of sleep-dependent enhancement/consolidation of a memory (solid line) depends on its initial strength (dashed line), being maximal and intermediate strengths. Ellipses indicate regions of the memory strength curve where greater initial strength leads to either increases (on left) or decreases (on right) in the extent of subsequent sleep-dependent consolidation, as depicted by arrows.
See this image and copyright information in PMC

Comment on

References

    1. Diekelmann S, Wilhelm I, Born J. The whats and whens of sleep-dependent memory consolidation. Sleep Med Rev. 2009 in press. - PubMed
    1. Walker MP, Stickgold R. Sleep-dependent learning and memory consolidation. Neuron. 2004 Sep 30;44(1):121–33. - PubMed
    1. Rechtschaffen A, Kales A. A manual of standardized terminology, techniques and scoring system for sleep stages of human subjects: Brain Information Service. University of California; Los Angeles: 1968. - PubMed
    1. Tulving E. How many memory systems are there? American Psychologist. 1985;40:385–98.
    1. Pace-Schott EF, Milad MR, Orr SP, Rauch SL, Stickgold R, Pitman RK. Sleep promotes generalization of extinction of conditioned fear. Sleep. 2009 Jan 1;32(1):19–26. - PMC - PubMed