Sleep-dependent neurophysiological processes in implicit sequence learning.
; ; Schmidt, Christina et al
in Journal of cognitive neuroscience (2013), 25(11), 2003-14
Behavioral studies have cast doubts about the role that posttraining sleep may play in the consolidation of implicit sequence learning. Here, we used event-related fMRI to test the hypothesis that sleep ... [more ▼]
Behavioral studies have cast doubts about the role that posttraining sleep may play in the consolidation of implicit sequence learning. Here, we used event-related fMRI to test the hypothesis that sleep-dependent functional reorganization would take place in the underlying neural circuits even in the possible absence of obvious behavioral changes. Twenty-four healthy human adults were scanned at Day 1 and then at Day 4 during an implicit probabilistic serial RT task. They either slept normally (RS) or were sleep-deprived (SD) on the first posttraining night. Unknown to them, the sequential structure of the material was based on a probabilistic finite-state grammar, with 15% chance on each trial of replacing the rules-based grammatical (G) stimulus with a nongrammatical (NG) one. Results indicated a gradual differentiation across sessions between RTs (faster RTs for G than NG), together with NG-related BOLD responses reflecting sequence learning. Similar behavioral patterns were observed in RS and SD participants at Day 4, indicating time- but not sleep-dependent consolidation of performance. Notwithstanding, we observed at Day 4 in the RS group a diminished differentiation between G- and NG-related neurophysiological responses in a set of cortical and subcortical areas previously identified as being part of the network involved in implicit sequence learning and its offline processing during sleep, indicating a sleep-dependent processing of both regular and deviant stimuli. Our results suggest the sleep-dependent development of distinct neurophysiological processes subtending consolidation of implicit motor sequence learning, even in the absence of overt behavioral differences. [less ▲]Detailed reference viewed: 12 (0 ULg)
Lateralized processing of false memories and pseudoneglect in aging.
; Dehon, Hedwige ; Peigneux, Philippe
in Cortex : A Journal Devoted to the Study of the Nervous System & Behavior (2012)
Aging is associated with higher propensity to false memories and decreased retrieval of previously studied items. When young adults perform on a lateralized version of the Deese-Roediger-McDermott (DRM ... [more ▼]
Aging is associated with higher propensity to false memories and decreased retrieval of previously studied items. When young adults perform on a lateralized version of the Deese-Roediger-McDermott (DRM) paradigm, the right cerebral hemisphere (RH) is more sensitive than the left (LH) to false memories, suggesting hemispheric imbalance in the cerebral mechanisms supporting semantic and episodic memory processes. Since cerebral asymmetries tend to be reduced with age, we surmised that behavioral asymmetries in the generation of false memories would be diminished with aging. To probe this hypothesis, a lateralized version of the DRM paradigm was administered to old (OA) and young (YA) healthy adults. During the encoding phase, lists of semantically associated words were memorized. During the retrieval session, targets (previously seen words), lures (never seen strongly semantically related words) and distracters (never seen, unrelated words) were briefly displayed either in the left or right visual fields, thus primarily stimulating the RH or LH, respectively. Participants had to decide whether the word was previously studied (Old/New), but also whether they had a strong episodic recollection (Remember) or a mere feeling of familiarity (Know) about Old words. In line with our predictions, false memories were globally higher in OA than YA, and vivid false recollections (i.e. Remember responses) were higher when lures were presented in the RH in YA, but not in OA. Additionally, we found significant correlations between YA participants’ familiarity scores and leftward attentional bias as previously evidenced using a visuospatial landmark task [Schmitz, R., and Peigneux, P. (2011). Age-related changes in visual pseudoneglect. Brain and Cognition, 76(3), 382-389], an effect not present in OA. This result is in line with the hypothesis of an interplay between attentional resources allocated to visuospatial and memory processes, suggesting a memory pseudoneglect phenomenon that would be altered with aging. [less ▲]Detailed reference viewed: 48 (2 ULg)
Cerebral asymmetries in sleep-dependent processes of memory consolidation
Peigneux, Philippe ; ; Willems, Sylvie
in Learning & Memory (2007), 14(6), 400-406
Preference for previously seen, unfamiliar objects reflects a memory bias on affective judgment, known as the "mere exposure effect" (MEE). Here, we investigated the effect of time, post-exposure sleep ... [more ▼]
Preference for previously seen, unfamiliar objects reflects a memory bias on affective judgment, known as the "mere exposure effect" (MEE). Here, we investigated the effect of time, post-exposure sleep, and the brain hemisphere solicited on preference generalization toward objects viewed in different perspectives. When presented in the right visual field (RVF), which promotes preferential processing in the left hemisphere, same and mirrored exemplars were preferred immediately after exposure. MEE generalized to much dissimilar views after three nights of sleep. Conversely, object presentation in the left visual field (LVF), promoting right hemisphere processing, elicited a MEE for same views immediately after exposure, then for mirror views after sleep. Most importantly, sleep deprivation during the first post-exposure night, although followed by two recovery nights, extinguished MEE for all views in the LVF but not in the RVF. Besides demonstrating that post-exposure time and sleep facilitate the generalization process by which we integrate various representations of an object, our results suggest that mostly in the right hemisphere, sleep may be mandatory to consolidate the memory bias underlying affective preference. These interhemispheric differences tentatively call for a reappraisal of the role of cerebral asymmetries in wake- and sleep-dependent processes of memory consolidation. [less ▲]Detailed reference viewed: 44 (2 ULg)