References of "Orban, Pierre"
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See detailPartially Segregated Neural Networks for Spatial and Contextual Memory in Virtual Navigation
Rauchs, G.; Orban, Pierre ULg; Balteau, Evelyne ULg et al

in Hippocampus (2008), 18(5), 503-518

Finding our way in a previously learned, ecologically valid environment concurrently involves spatial and contextual cognitive operations. The former process accesses a cognitive map representing the ... [more ▼]

Finding our way in a previously learned, ecologically valid environment concurrently involves spatial and contextual cognitive operations. The former process accesses a cognitive map representing the spatial interactions between all paths in the environment. The latter accesses stored associations between landmark objects and their milieu. Here, we aimed at dissociating their neural basis in the context of memory-based virtual navigation. To do so, subjects freely explored a virtual town for 1 h, then were scanned using fMRI while retrieving their way between two locations, under four navigation conditions designed to probe separately or jointly the spatial and contextual memory components. Besides prominent commonalities found in a large hippocampo-neocortical network classically involved in topographical navigation, results yield evidence for a partial dissociation between the brain areas supporting spatial and contextual components of memory-based navigation. Performance-related analyses indicate that hippocampal activity mostly supports the spatial component, whereas parahippocampal activity primarily supports the contextual component. Additionally, the recruitment of contextual memory during navigation was associated with higher frontal, posterior parietal and lateral temporal activity. These results provide evidence for a partial segregation of the neural substrates of two crucial memory components in human navigation, whose combined involvement eventually leads to efficient navigation behavior within a learned environment. (c) 2008 Wiley-Liss, Inc. [less ▲]

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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 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 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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