The Journal of Neuroscience, June 1, 2002, 22(11):4702-4708
Effects of Prolonged Waking-Auditory Stimulation on
Electroencephalogram Synchronization and Cortical Coherence during
Subsequent Slow-Wave Sleep
Jose L.
Cantero,
Mercedes
Atienza,
Rosa M.
Salas, and
Elena
Dominguez-Marin
Laboratory of Sleep and Cognition, 41005 Seville, Spain
Evidence suggests that sleep homeostasis is not only dependent on
duration of previous wakefulness but also on experience- and/or
use-dependent processes. Such homeostatic mechanisms are reflected by
selective increases in the duration of a sleep stage, modifications to
electrophysiological-metabolic brain patterns in specific sleep
states, and/or reactivation to neuronal ensembles in subsequent sleep
periods. Use-dependent sleep changes, apparently different from those
changes caused by memory consolidation processes, are thought to
reflect neuronal restoration processes after the sustained exposure to
stimulation during the preceding wakefulness. In the present study, we
investigated changes in the brain electrical activity pattern during
human sleep after 6 hr of continuous auditory stimulation during
previous wakefulness. Poststimulation nights showed a widespread
increase of spectral power within the
(8-12 Hz) and sleep
spindle (12-15 Hz) frequency range during slow-wave sleep (SWS)
compared with the baseline night. This effect was mainly
attributable to an enhanced EEG amplitude rather than an increase of oscillations, except for temporal (within
and sleep spindles) and parietal regions (within sleep spindles) in which both
parameters contributed equally to the increase of spectral energy.
Power increments were accompanied by a strengthening of the coherence
between fronto-temporal cortical regions within a broad frequency range
during SWS but to the detriment of the coherence between temporal and
parieto-occipital areas, suggesting underlying compensatory mechanisms
between temporal and other cortical regions. In both cases, coherence
was built up progressively across the night, although no changes were
observed within each SWS period. No electrophysiological changes were
found in rapid eye movement sleep.
These results point to SWS as a critical brain period for correcting
the cortical synaptic imbalance produced by the predominant use of
specific neuronal populations during the preceding wakefulness, as well
as for synaptic reorganization after prolonged exposure to a novel
sensory experience.
Key words:
slow-wave sleep; sleep spindles;
activity; spectral
analysis; coherence; sleep homeostasis; use-dependent function of
sleep
Copyright © 2002 Society for Neuroscience 0270-6474/02/22114702-07$05.00/0