Why do we sleep?
Brain Research
Volume 886, Issues 1-2, 15 December 2000, Pages 208-223
Copyright © 2000 Elsevier Science B.V. All rights reserved.
Interactive report

Why do we sleep?1

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Terrence J. Sejnowski Corresponding Author Contact Information, E-mail The Corresponding Author, a, b and Alain Destexhec

a Howard Hughes Medical Institute and the Salk Institute, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA

b Department of Biology, University of California at San Diego, La Jolla, CA 92093, USA

c Unite de Neurosciences Integratives et Computationnelles, CNRS, UPR-2191, Avenue de la Terrasse, 91198 Gif-sur-Yvette, France

Accepted 8 October 2000.
Available online 12 December 2000.


Slow-wave sleep consists in slowly recurring waves that are associated with a large-scale spatio-temporal synchrony across neocortex. These slow-wave complexes alternate with brief episodes of fast oscillations, similar to the sustained fast oscillations that occur during the wake state. We propose that alternating fast and slow waves consolidate information acquired previously during wakefulness. Slow-wave sleep would thus begin with spindle oscillations that open molecular gates to plasticity, then proceed by iteratively ‘recalling’ and ‘storing’ information primed in neural assemblies. This scenario provides a biophysical mechanism consistent with the growing evidence that sleep serves to consolidate memories.

Author Keywords: Slow-wave sleep; Spindle oscillation; Spatio-temporal synchrony; Synaptic plasticity; Memory consolidation; Computational model; Rapid eye movement sleep

Article Outline

1. Introduction
2. Brain rhythms during sleep

2.1. Delta oscillations
2.2. Spindle oscillations
2.3. Arousal
2.4. Rapid eye movement (REM) sleep
2.5. Fast oscillations

3. Biophysical aspects of sleep oscillations

3.1. Characterization of the effect of thalamic inputs in neocortical pyramidal neurons
3.2. Spatiotemporal structure of slow-wave sleep oscillations
3.3. A biophysically-based hypothesis for network reorganization during sleep

4. Sleep and memory consolidation

4.1. Hippocampus, neocortex and retrograde amnesia
4.2. Computational models of sleep
4.3. Interactions between the hippocampus and the neocortex
4.4. Temporally asymmetric hebbian plasticity
4.5. Thalamocortical assemblies

5. Conclusions

1 Published on the World Wide Web on 7 November 2000.

Corresponding Author Contact Information Corresponding author. The Salk Institute, Computational Neurobiology Laboratory, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA. Tel.: +1-858-453-4100; fax: +1-858-587-0417; email: terry@salk.edu
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