References of "Luxen, André"
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See detailBrain responses to violet, blue, and green monochromatic light exposures in humans: prominent role of blue light and the brainstem
Vandewalle, Gilles ULg; Schmidt, Christina ULg; Albouy, Geneviève ULg et al

in PLoS ONE (2007), 2(11), 1247

BACKGROUND: Relatively long duration retinal light exposure elicits nonvisual responses in humans, including modulation of alertness and cognition. These responses are thought to be mediated in part by ... [more ▼]

BACKGROUND: Relatively long duration retinal light exposure elicits nonvisual responses in humans, including modulation of alertness and cognition. These responses are thought to be mediated in part by melanopsin-expressing retinal ganglion cells which are more sensitive to blue light than violet or green light. The contribution of the melanopsin system and the brain mechanisms involved in the establishment of such responses to light remain to be established. METHODOLOGY/PRINCIPAL FINDINGS: We exposed 15 participants to short duration (50 s) monochromatic violet (430 nm), blue (473 nm), and green (527 nm) light exposures of equal photon flux (10(13)ph/cm(2)/s) while they were performing a working memory task in fMRI. At light onset, blue light, as compared to green light, increased activity in the left hippocampus, left thalamus, and right amygdala. During the task, blue light, as compared to violet light, increased activity in the left middle frontal gyrus, left thalamus and a bilateral area of the brainstem consistent with activation of the locus coeruleus. CONCLUSION/SIGNIFICANCE: These results support a prominent contribution of melanopsin-expressing retinal ganglion cells to brain responses to light within the very first seconds of an exposure. The results also demonstrate the implication of the brainstem in mediating these responses in humans and speak for a broad involvement of light in the regulation of brain function. [less ▲]

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See detailHemodynamic cerebral correlates of sleep spindles during human non-rapid eye movement sleep.
Schabus, Manuel ULg; Dang Vu, Thien Thanh ULg; Albouy, Geneviève ULg et al

in Proceedings of the National Academy of Sciences of the United States of America (2007), 104(32), 13164-9

In humans, some evidence suggests that there are two different types of spindles during sleep, which differ by their scalp topography and possibly some aspects of their regulation. To test for the ... [more ▼]

In humans, some evidence suggests that there are two different types of spindles during sleep, which differ by their scalp topography and possibly some aspects of their regulation. To test for the existence of two different spindle types, we characterized the activity associated with slow (11-13 Hz) and fast (13-15 Hz) spindles, identified as discrete events during non-rapid eye movement sleep, in non-sleep-deprived human volunteers, using simultaneous electroencephalography and functional MRI. An activation pattern common to both spindle types involved the thalami, paralimbic areas (anterior cingulate and insular cortices), and superior temporal gyri. No thalamic difference was detected in the direct comparison between slow and fast spindles although some thalamic areas were preferentially activated in relation to either spindle type. Beyond the common activation pattern, the increases in cortical activity differed significantly between the two spindle types. Slow spindles were associated with increased activity in the superior frontal gyrus. In contrast, fast spindles recruited a set of cortical regions involved in sensorimotor processing, as well as the mesial frontal cortex and hippocampus. The recruitment of partially segregated cortical networks for slow and fast spindles further supports the existence of two spindle types during human non-rapid eye movement sleep, with potentially different functional significance. [less ▲]

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See detailSleep-related hippocampo-cortical interplay during emotional memory recollection.
Sterpenich, Virginie ULg; Albouy, Geneviève ULg; Boly, Mélanie ULg et al

in PLoS Biology (2007), 5(11), 282

Emotional events are usually better remembered than neutral ones. This effect is mediated in part by a modulation of the hippocampus by the amygdala. Sleep plays a role in the consolidation of declarative ... [more ▼]

Emotional events are usually better remembered than neutral ones. This effect is mediated in part by a modulation of the hippocampus by the amygdala. Sleep plays a role in the consolidation of declarative memory. We examined the impact of sleep and lack of sleep on the consolidation of emotional (negative and positive) memories at the macroscopic systems level. Using functional MRI (fMRI), we compared the neural correlates of successful recollection by humans of emotional and neutral stimuli, 72 h after encoding, with or without total sleep deprivation during the first post-encoding night. In contrast to recollection of neutral and positive stimuli, which was deteriorated by sleep deprivation, similar recollection levels were achieved for negative stimuli in both groups. Successful recollection of emotional stimuli elicited larger responses in the hippocampus and various cortical areas, including the medial prefrontal cortex, in the sleep group than in the sleep deprived group. This effect was consistent across subjects for negative items but depended linearly on individual memory performance for positive items. In addition, the hippocampus and medial prefrontal cortex were functionally more connected during recollection of either negative or positive than neutral items, and more so in sleeping than in sleep-deprived subjects. In the sleep-deprived group, recollection of negative items elicited larger responses in the amygdala and an occipital area than in the sleep group. In contrast, no such difference in brain responses between groups was associated with recollection of positive stimuli. The results suggest that the emotional significance of memories influences their sleep-dependent systems-level consolidation. The recruitment of hippocampo-neocortical networks during recollection is enhanced after sleep and is hindered by sleep deprivation. After sleep deprivation, recollection of negative, potentially dangerous, memories recruits an alternate amygdalo-cortical network, which would keep track of emotional information despite sleep deprivation. [less ▲]

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See detailHere I am: the cortical correlates of visual self-recognition.
Devue, Christel ULg; Collette, Fabienne ULg; Balteau, Evelyne ULg et al

in Brain Research (2007), 1143

Recently, interest in the neural correlates of self-recognition has grown. Most studies concentrate on self-face recognition. However, there is a lack of convergence as to precise neuroanatomical ... [more ▼]

Recently, interest in the neural correlates of self-recognition has grown. Most studies concentrate on self-face recognition. However, there is a lack of convergence as to precise neuroanatomical locations underlying self-face recognition. In addition, recognition of familiar persons from bodies has been relatively neglected. In the present study, cerebral activity while participants performed a task in which they had to indicate the real appearance of themselves and of a gender-matched close colleague among intact and altered pictures of faces and bodies was measured. The right frontal cortex and the insula were found to be the main regions specifically implicated in visual self-recognition compared with visual processing of other highly familiar persons. Moreover, the right anterior insula along with the right anterior cingulate seemed to play a role in the integration of information about oneself independently of the stimulus domain. The processing of self-related pictures was also compared to scrambled versions of these pictures. Results showed that different areas of the occipito-temporal cortex were more or less recruited depending on whether a face or a body was perceived, as it has already been reported by several recent studies. The implication of present findings for a general framework of person identification is discussed. [less ▲]

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See detailEffects of attention on emotional face processing in depression: an fMRI study.
Desseilles, Martin ULg; Maquet, Pierre ULg; Sterpenich, Virginie et al

Poster (2006, November 18)

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See detailThe role of sleep in motor memory consolidation assessed by fMRI
Albouy, Geneviève ULg; Sterpenich, Virginie ULg; Darsaud, A. et al

in Journal of Sleep Research (2006, September), 15(Suppl. 1), 189

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See detailSleep-dependent changes in brain activity subserving human navigation
Rauchs, G.; Orban, Pierre ULg; Schmidt, Christina ULg et al

in Journal of Sleep Research (2006, September), 15(Suppl. 1), 189-190

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See detailThe locus ceruleus is involved in the successful retrieval of emotional memories in humans
Sterpenich, Virginie ULg; D'Argembeau, Arnaud ULg; Desseilles, Martin ULg et al

in Journal of Neuroscience (2006), 26(28), 7416-7423

Emotional memories are better remembered than neutral ones. The amygdala is involved in this enhancement not only by modulating the hippocampal activity, but possibly also by modulating central arousal ... [more ▼]

Emotional memories are better remembered than neutral ones. The amygdala is involved in this enhancement not only by modulating the hippocampal activity, but possibly also by modulating central arousal. Using functional magnetic resonance imaging, we analyzed the retrieval of neutral faces encoded in emotional or neutral contexts. The pupillary size measured during encoding was used as a modulator of brain responses during retrieval. The interaction between emotion and memory showed significant responses in a set of areas, including the amygdala and parahippocampal gyrus. These areas responded significantly more for correctly remembered faces encoded in an emotional, compared with neutral, context. The same interaction conducted on responses modulated by the pupillary size revealed an area of the dorsal tegmentum of the ponto-mesencephalic region, consistent with the locus ceruleus. Moreover, a psychophysiological interaction showed that amygdalar responses were more tightly related to those of the locus ceruleus when remembering faces that had been encoded in an emotional, rather than neutral, context. These findings suggest that the restoration of a central arousal similar to encoding takes part in the successful retrieval of neutral events learned in an emotional context. [less ▲]

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See detailRadiochemical synthesis and tissue distribution of p-[F-18]DMPPF, a new 5-HT1A ligand for PET, in rats
Defraiteur, Caroline; Lemaire, Christian ULg; Luxen, André ULg et al

in Nuclear Medicine & Biology (2006), 33(5), 667-675

Several studies have demonstrated the potential of p-[F-18]MPPF as a radiophanilaceutical to study the 5-HT1A receptor family in animals and humans. A structural modification leading to a higher ... [more ▼]

Several studies have demonstrated the potential of p-[F-18]MPPF as a radiophanilaceutical to study the 5-HT1A receptor family in animals and humans. A structural modification leading to a higher radioactive signal at an equipotent dose would greatly enhance this potential. With this goal, the desmethylated 4-(2'-methoxyphenyl)-1-[2'-[N-(2"-pyridinyl)-p-fluorobenzamidolethyl]-piperazine (p-MPPF), identified as p-DMPPF, was synthesized, labeled with fluorine-18 and evaluated through ex vivo tissue distribution in rats. The new compounds p-DMPPF, p-DMPPNO2, MEM-p-MPPF and MEM-p-MPPNO2 were isolated and fully identified (H-1 and C-13 NMR, LC-MS). The final compound, p-[F-18]DMPPF, was obtained ready for injection, with an overall radiochemical yield of 10% (EOB corrected) within 90 min and a specific activity of 62 GBq/mu mol. Tissue distributions showed that the carbon-fluorine bond was stable in vivo and that this compound could cross the blood-brain barrier. For kidney, lung, heart, spleen, bone, testicle, liver and muscle, the percentage of injected dose per gram of tissue obtained with p-[F-18]DMPPF was of the same order of magnitude as that of p-[F-18]MPPF. The amount of radioactivity reaching the brain was much higher (approximately fivefold at 60 min) for p-[F-18]DMPPF compared with p-[F-18]MPPF, which was taken as reference. The distribution and specificity were in total agreement with the known localization of 5-HT1A receptors in rats. The radioactivity increase was more important for specific tissues (hippocampus and frontal cortex) than for cerebellum or striatum, leading to better contrast (hippocampus/cerebellum=5.8 at 60 min). The levels of metabolites found in plasma showed that p-[F-18]DMPPF appears to be less metabolized than p-[F-18]MPPF. p-[F-18]DMPPF deserves further evaluation as a radiopharmaceutical candidate. (c) 2006 Elsevier Inc. All rights reserved. [less ▲]

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See detailImplicit oculomotor sequence learning in humans: Time course of offline processing
Albouy, Geneviève ULg; Ruby, P.; Phillips, Christophe ULg et al

in Brain Research (2006), 1090

Studies of manual and digital sequence learning indicate that motor memories continue to be processed after training has ended, following a succession of identifiable steps. However, it is not known ... [more ▼]

Studies of manual and digital sequence learning indicate that motor memories continue to be processed after training has ended, following a succession of identifiable steps. However, it is not known whether this offline memory processing constitutes a basic feature of motor learning and generalizes to the implicit learning of a sequence of eye movements. To assess this hypothesis, we have created the serial oculomotor reaction time task (SORT). Participants were trained to the SORT then tested after either 30 min, 5 h or 24 h. During training, ocular reaction times decreased monotonically over practice of a repeated sequence, then increased when a different sequence was displayed, demonstrating oculomotor learning of the trained sequence. When tested 30 min after training, a significant gain in oculomotor performance was observed irrespective of the sequence learning. This gain was no longer present after 5 h. Remarkably, a gain in performance specific to the learned sequence emerged only 24 h after training. After testing, a generation task confirmed that most subjects learned implicitly the regularities of the sequence. Our results show that, as for manual or digital sequences, oculomotor sequences can be implicitly learned. The offline processing of oculomotor memories follows distinct stages in a way similar to those observed after manual or digital sequence learning. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailSynthesis of anhydro-muramic acid derivatives as substrates for MurNAc amidase
Mercier, Frédéric; Lemaire, Christian ULg; Plenevaux, Alain ULg et al

Poster (2006, May 17)

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See detailSleep after spatial learning promotes covert reorganization of brain activity
Orban, Pierre ULg; Rauchs, Géraldine; Balteau, Evelyne ULg et al

in Proceedings of the National Academy of Sciences of the United States of America (2006), 103(18), 7124-7129

Sleep promotes the integration of recently acquired spatial memories into cerebral networks for the long term. In this study, we examined how sleep deprivation hinders this consolidation process. Using ... [more ▼]

Sleep promotes the integration of recently acquired spatial memories into cerebral networks for the long term. In this study, we examined how sleep deprivation hinders this consolidation process. Using functional MRI, we mapped regional cerebral activity during place-finding navigation in a virtual town, immediately after learning and 3 days later, in subjects either allowed regular sleep (RS) or totally sleep-deprived (TSD) on the first posttraining night. At immediate and delayed retrieval, place-finding navigation elicited increased brain activity in an extended hippocamponeocortical network in both RS and TSD subjects. Behavioral performance was equivalent between groups. However, striatal navigation-related activity increased more at delayed retrieval in RS than in TSD subjects. Furthermore, correlations between striatal response and behavioral performance, as well as functional connectivity between the striatum and the hippocampus, were modulated by posttraining sleep. These data suggest that brain activity is restructured during sleep in such a way that navigation in the virtual environment, initially related to a hippocampus-dependent spatial strategy, becomes progressively contingent in part on a response-based strategy mediated by the striatum. Both neural strategies eventually relate to equivalent performance levels, indicating that covert reorganization of brain patterns underlying navigation after sleep is not necessarily accompanied by overt changes in behavior. [less ▲]

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See detailDecomposition of metabolic brain clusters in the frontal variant of frontotemporal dementia
Salmon, Eric ULg; Kerrouche, Nacer; Herholz, Karl et al

in NeuroImage (2006), 30(3), 871-878

Previous studies that measured brain activity in frontotemporal dementia (FTD) used univariate analyses, examining each region of interest separately. We explored in a multicenter European research ... [more ▼]

Previous studies that measured brain activity in frontotemporal dementia (FTD) used univariate analyses, examining each region of interest separately. We explored in a multicenter European research program the principal brain clusters characterized by a common variability in cerebral metabolism in FTD. Seventy patients with frontal variant (fv) FTD were selected according to international clinical recommendations; principal component analysis (PCA) was performed on FDG-PET metabolic images, looking for covariance clusters in this large population. A first metabolic cluster included most of the lateral and medial prefrontal cortex, bilaterally; PC1 scores correlated with performances on memory and executive neuropsychological tasks. Moreover, FDG-PET images in fv-FTD were further characterized by a metabolic covariance in two clusters comprising the subcallosal medial frontal region, the temporal pole, medial temporal structures and the striatum, separately in the left and in the right hemisphere. The study provides original data-driven arguments for metabolic involvement of separate brain clusters in the rostral limbic system, corresponding to pathological poles differentially affected in each FTD patient. [less ▲]

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See detailOffline persistence of memory-related cerebral activity during active wakefulness
Peigneux, Philippe ULg; Orban, Pierre ULg; Balteau, Evelyne ULg et al

in PLoS Biology (2006), 4(4), 100

Much remains to be discovered about the fate of recent memories in the human brain. Several studies have reported the reactivation of learning-related cerebral activity during post-training sleep ... [more ▼]

Much remains to be discovered about the fate of recent memories in the human brain. Several studies have reported the reactivation of learning-related cerebral activity during post-training sleep, suggesting that sleep plays a role in the offline processing and consolidation of memory. However, little is known about how new information is maintained and processed during post-training wakefulness before sleep, while the brain is actively engaged in other cognitive activities. We show, using functional magnetic resonance imaging, that brain activity elicited during a new learning episode modulates brain responses to an unrelated cognitive task, during the waking period following the end of training. This post-training activity evolves in learning-related cerebral structures, in which functional connections with other brain regions are gradually established or reinforced. It also correlates with behavioral performance. These processes follow a different time course for hippocampus-dependent and hippocampus-independent memories. Our experimental approach allowed the characterization of the offline evolution of the cerebral correlates of recent memories, without the confounding effect of concurrent practice of the learned material. Results indicate that the human brain has already extensively processed recent memories during the first hours of post-training wakefulness, even when simultaneously coping with unrelated cognitive demands. [less ▲]

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See detailDEVELOPPEMENT D'INHIBITEURS SELECTIFS DE LA TRYPTOPHANE HYDROXYLASE
Giacomelli, Fabrice ULg; Luxen, André ULg; Lemaire, Christian ULg et al

Conference (2006, February 03)

Comprendre la façon dont le cerveau travaille et en particulier le mode de communication de ses cellules est un rêve que beaucoup de chercheurs caressent. A l’heure actuelle, une des rares certitudes à ... [more ▼]

Comprendre la façon dont le cerveau travaille et en particulier le mode de communication de ses cellules est un rêve que beaucoup de chercheurs caressent. A l’heure actuelle, une des rares certitudes à son sujet est qu’un de ses modes de transmission d’informations utilise des « messagers » chimiques appelés neurotransmetteurs. Parmi ceux-ci, la sérotonine (5-HT) revêt une importance particulière. En effet, la 5-HT est impliquée dans de nombreuses fonctions (apprentissage, locomotion, sommeil,…) et pathologies (dépressions, démences, schizophrénies,…). Dès lors, l'étude in vivo chez l'homme des neurones sérotoninergiques ainsi que la quantification de la vitesse de biosynthèse de la 5-HT sont des domaines d'études fondamentaux pour lesquels la tomographie à émission de positons (TEP) constitue un outil de choix. Pour mener à bien ces différentes expérimentations, deux stratégies sont envisageables : - L’emploi d'un traceur capable de suivre la chaîne métabolique du tryptophane conduisant à la 5-HT tout en évitant les autres voies métaboliques. - L’utilisation d'un inhibiteur de la TrpOH (enzyme limitant du processus). Dans le cadre de cette présentation, nous nous intéresserons plus particulièrement à la deuxième stratégie. [less ▲]

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See detailThe role of sleep in the consolidation of emotional memories W
Sterpenich, V.; Albouy, G.; Boly, M. et al

Poster (2006)

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See detailL-amino acid load to enhance PET differentiation between tumor and inflammation: an in vitro study on (18)F-FET uptake.
Laique, S.; Egrise, D.; Monclus, M. et al

in Contrast Media & Molecular Imaging (2006), 1(5), 212-20

Labeled amino acids (AA) are tumor tracers for use in nuclear medecine. O-(2-[(18)F]fluoroethyl)-L-tyrosine (FET) is transported by the L-system, known to function as an exchanger. In vitro utilization of ... [more ▼]

Labeled amino acids (AA) are tumor tracers for use in nuclear medecine. O-(2-[(18)F]fluoroethyl)-L-tyrosine (FET) is transported by the L-system, known to function as an exchanger. In vitro utilization of FET, after a preload or prior to an afterload of non radioactive L-amino acids, was evaluated in order to measure the potential effects of AA content on the distinction between tumor and inflammatory lesions. Cellular uptake of FET was studied on rat osteosarcoma cells (ROS 17/2.8) and human leukocytes, initially loaded with nonradioactive L-tyrosine or L-methionine. FET efflux was evaluated from cells loaded with nonradioactive L-phenylalanine after tracer uptake. ROS 17/2.8 showed a higher sensitivity to preload and afterload effects on cellular FET content as compared with the leukocytes. We conclude that preload with L-tyrosine, prior to the administration of FET, may be a potential procedure to improve PET differentiation between tumor and inflammatory lesions. [less ▲]

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See detailImproved PRESS sequence for lactate detection in the human vitreous body
Balteau, Evelyne ULg; COLLIGNON, Nathalie ULg; Robe, Pierre ULg et al

in Proceedings of the International Society for Magnetic Resonance in Medicine (2006), 14

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