Verslag – Rapport – Bericht – Report - GSKE - FMRE

magnetic resonance imaging (fMRI), we assessed the influence of chronotype and time-ofday
on conflict processing-related cerebral activity throughout a normal waking day. Sixteen
morning and 15 evening types were recorded at two individually adapted time points (1.5 versus
10.5 hours spent awake) while performing the Stroop paradigm. Results show that interferencerelated
hemodynamic responses are maintained or even increased in evening types from the
subjective morning to the subjective evening in a set of brain areas playing a pivotal role in
successful inhibitory functioning, whereas they decreased in morning types under the same
conditions. Furthermore, during the evening hours, activity in a posterior hypothalamic region
putatively involved in sleep-wake regulation correlated in a chronotype-specific manner with
slow wave activity at the beginning of the night, an index of accumulated homeostatic sleep
pressure. These results shed light into the cerebral mechanisms underlying inter-individual
differences of higher-order cognitive state maintenance under normally entrained day-night
conditions.
Schmidt C, Peigneux P, Leclercq Y, Sterpenich V, Vandewalle G, Phillips C, Berthomier P,
Berthomier C, Tinguely G, Gais S, Schabus M, Desseilles M, Dang-Vu T, Salmon E, Degueldre
C, Balteau E, Luxen A, Cajochen C, Maquet P, Collette F (2012) Circadian Preference Modulates
the Neural Substrate of Conflict Processing across the Day. PLoS One 7:e29658.
Otherwise, we published the latest analyses of EEG/fMRI data, on the characterization of
spontaneous brain activity during normal human sleep and anesthesia
Consciousness is reduced during NREM sleep due to changes in brain function which are still
poorly understood. We tested the hypothesis that impaired consciousness during NREM sleep
is associated with an increased modularity of brain activity. Cerebral connectivity was quantified
in resting-state functional magnetic resonance imaging times series acquired in thirteen healthy
volunteers during wakefulness and NREM sleep. The analysis revealed a modification of the
hierarchical organization of large-scale networks into smaller independent modules during
NREM sleep, independently from EEG markers of the slow oscillation. Such modifications in
brain connectivity, possibly driven by sleep ultra-slow oscillations, could hinder the brain’s ability
to integrate information and account for decreased consciousness during NREM sleep.
These results are now published : Boly M, Perlbarg V, Marrelec G, Schabus M, Laureys S, Doyon
J, Pelegrini-Issac M, Maquet P, Benali H (2012) Hierarchical clustering of brain activity during
human nonrapid eye movement sleep. Proc Natl Acad Sci U S A 109:5856-5861.
The present study aimed at identifying the neurophysiological responses associated with
auditory stimulation during non-rapid eye movement (NREM) sleep using simultaneous
electroencephalography (EEG)/functional magnetic resonance imaging (fMRI) recordings. It was
reported earlier that auditory stimuli produce bilateral activation in auditory cortex, thalamus,
and caudate during both wakefulness and NREM sleep. However, due to the spontaneous
membrane potential fluctuations cortical responses may be highly variable during NREM. Here
we now examine the modulation of cerebral responses to tones depending on the presence or
absence of sleep spindles and the phase of the slow oscillation. Thirteen healthy young subjects
were scanned successfully during stage 2-4 NREM sleep in the first half of the night in a 3 T
scanner. Subjects were not sleep-deprived and sounds were post hoc classified according to
(i) the presence of sleep spindles or (ii) the phase of the slow oscillation during (+/-300 ms) tone
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Verslag – Rapport – Report 2012