Biology subjects

Boutin, A.

Publications and source records attributed to Boutin, A..

9 recordsLinked to original sources

bioRxiv2026

Characterising sleep spindle emergence in infancy: Effects of prematurity and early locomotor intervention

Study objectives: Sleep spindles are thalamocortical oscillations evolving during early brain maturation. In adults, they support memory consolidation and are organised into rhythmic "trains" thought to support memory reactivation. How this temporal organisation emerges in infancy, and whether prematurity or early sensorimotor experience shapes it, remains unclear. This study characterised infant spindles and investigated how prematurity and early locomotor training affect their temporal and spatial organisation, providing insight into early brain maturation. Methods: Daytime high-density EEG sleep recordings were analysed in 50 infants born full-term (n=12) or very preterm (n=38, including 12 who received locomotor training) at 2 months corrected age. Spindle temporal organisation was analysed using a two-step Morlet wavelet transform to quantify slow modulations of spindle-band power (11-16Hz). Time-frequency decomposition around spindle onset was used to identify significant spindle-band scalp-wide activity, and topographical maps were statistically compared between groups. Results: All groups showed rhythmic spindle organisation, three times slower than in adults, with no group differences. Untrained preterm infants showed a more diffuse spindle-band activity than the distinct frontal and central clusters observed in full-term infants. Trained preterm infants exhibited a spatial distribution closely resembling that of full-term infants, although their frontal spindle density was lower than in both other groups. Conclusions: Spindle rhythmic organisation emerged early in infancy and remained unaffected by prematurity or locomotor training. Prematurity was associated with more diffuse spindle-band activity, suggesting reduced cortical specialisation, whereas trained preterm infants showed a spatial distribution resembling that of full-term infants, suggesting that early locomotor experience may influence thalamocortical organisation.

neuroscience↗

bioRxiv2026

Sleep Spindle-Locked Targeted Memory Reactivation Enhances Declarative Memory Consolidation

Study ObjectivesSleep spindles are implicated in memory consolidation. Yet direct evidence linking spindle dynamics to declarative memory outcomes remains limited. We thus tested whether targeted memory reactivation (TMR) time-locked to sleep spindles enhances declarative memory, and whether the temporal organization of stimulated spindles-trains versus isolated events-is selectively associated with distinct memory outcomes. MethodsTwenty-eight healthy young adults learned image locations from two categories (animals, clothing) in a grid, each paired with a distinct auditory cue. During overnight NREM sleep, one cue was replayed time-locked to spindles detected in real-time using a closed-loop system (TMR condition); the other served as the non-reactivated control (No-TMR condition). Category-cue assignment was counterbalanced. Post-sleep recall, recognition accuracy, and movement time were assessed. ResultsRecall accuracy was significantly higher in the TMR than the No-TMR condition (93.96% vs. 90.61%, p = .024), whereas recognition accuracy (p = .139) and movement time (p = .651) did not differ. Stimulation intensity within spindle trains correlated with the TMR effect on recall (Spearman {rho} = .531, p = .004), whereas the proportion of isolated spindle stimulations correlated with the TMR effect on recognition ({rho} = .563, p = .002). Cross-associations were not significant. ConclusionsSpindle-locked TMR enhances recall-based declarative memory retention. The selective association between spindle temporal clustering and memory outcomes suggests that train-embedded and isolated spindles support different aspects of memory consolidation, highlighting spindle temporal context as a functionally relevant dimension of sleep-dependent memory processing.

neuroscience↗

bioRxiv2025

Slow Spindle Trains During Daytime Naps are Associated with Improved Declarative Memory Consolidation

Memory consolidation refers to the process by which newly encoded memories are strengthened and retained over time, and ample evidence indicates that sleep supports this process for both procedural and declarative memories. Although sleep spindles during non-rapid eye movement (NREM) sleep have been associated to consolidation, it remains unclear whether all spindle types contribute equally. Spindles vary in frequency and topography-slow spindles ([≤]12.5Hz) predominating over frontal regions, whereas fast spindles (>12.5Hz) peak parietally - and recent work suggests that procedural memory consolidation during overnight sleep is related to the temporal organization of spindles in trains (i.e., events occurring <6s apart). Here we investigated whether a similar mechanism operates for declarative memory during daytime naps. Participants were assigned to a Nap (N=23) or No-Nap (N=15) group, and completed an object-spatial location task involving 36 item-location associations. Memory was assessed immediately after learning and again following a 90-minute nap or an equivalent wake period. Results showed that the Nap group exhibited significantly better delayed memory, as measured by combined recall-recognition score, and a greater proportion of participants maintained or improved their performance. In the Nap group, memory performance correlated with local spindle density at frontal and parietal sites, and, critically, with the proportion of slow spindles clustered in trains during NREM2. These findings suggest the temporal organization of slow spindles into clusters support declarative memory consolidation, pointing to a shared spindle-based mechanism across domains.

neuroscience↗

bioRxiv2025

Evidence for separate processes underlying movement and decision vigor in a reward-oriented task

The vigor of movement and decision-making is fundamental to many reward-oriented behaviors. While some theories propose that movement and decision are jointly invigorated to maximize a global utility (e.g., mixing reward, effort, and time), alternative perspectives suggest that the brain can separately invigorate them when advantageous. We tested these competing hypotheses using a foraging-like task that allowed experimentally assessing the vigor of movement (reaching to reward location) and that of decision-making (harvesting reward). By using a block-wise design, we measured the effects of independent manipulations of time and effort on reach and harvest durations. Decoupled effects were found on reach and harvest durations, with no inter-individual consistency between them. A model allowing separate, yet inter-dependent, optimizations of movement and decision vigor based on distinct time costs sensitive to recent temporal history predicted these results more accurately than a global utility model. These findings indicate that movement and decision vigor may flexibly depend on whether shared versus distinct time costs underlie behavior; co-regulation would arise when the vigor of movement and decision is governed by a shared time cost but decoupling may emerge when relevant for the task. Significance statementCoordinating movement and decision-making is fundamental to many reward-oriented behaviors. Current theories suggest that the brain may invigorate behavior by co-regulating movement and decision, but some experimental findings rather point to a decoupling. To shed new light on this debate, we developed a foraging-like task promoting independent and comparable manipulation of time and effort. We show that movement and decision are mostly decoupled in this task, invigorated by distinct time-cost signals. Previously experienced delays tend to amplify these time costs, thereby exerting a strong influence on behavior and indirectly linking movement and decision. Co-regulation or decoupling may hinge on whether movement and decision vigor relies on shared or distinct time-cost signals.

neuroscience↗

bioRxiv2024

Sensorimotor restriction affects sleep-related motor memory consolidation through altered slow oscillation-spindle coupling.

Sleep benefits memory consolidation through periodic sleep spindle activity and associated memory reactivations. Recent evidence highlights that iterative spindle onsets follow two periodic rhythms: an infraslow periodicity ([~]0.02 Hz) and a mesoscale periodicity rhythm ([~]0.2-0.3 Hz). Consequently, spindles tend to cluster in "trains" on a low-frequency time scale every 50 seconds during which spindles iterate every 3 to 4 seconds. Such temporal organization of spindles in trains is considered a critical sleep mechanism for the timed and repeated reactivation of memories. Additionally, current trends indicate that a timely phase-locking between slow oscillations (SO) and spindles promotes learning-related synaptic plasticity. In this study, we explored how spindle clustering and coupling with SO contribute to motor memory consolidation by inducing a local reduction in synaptic efficacy over sensorimotor cortical regions through upper-limb immobilization after motor sequence learning. We also evaluated memory generalization using two transfer tests designed to assess the ability to transfer or generalize the newly acquired skill to another one (new sequence) or another effector (inter-limb transfer). Our results reveal that the temporal cluster-based organization of spindles is independent of daytime sensorimotor experience, while distinct overnight behavioral outcomes were elicited. Interestingly, immobilization induced a phase shift in the SO-spindle coupling for spindles grouped in trains, but not when isolated outside trains. In addition, the proportion of grouped spindles relative to isolated spindles was positively associated with skill consolidation and negatively correlated with skill generalization following sensorimotor restriction. These results suggest that spindle trains may promote skill-specific strengthening of motor memories, while isolated spindles may instead create memory-instability conditions that facilitate skill generalization.

neuroscience↗

bioRxiv2022

Temporal clustering of sleep spindles for motor skill consolidation and generalizability following learning by physical practice, motor imagery and action observation

Sleep benefits the consolidation of motor skills learned by physical practice, mainly through periodic thalamocortical sleep spindle activity. However, motor skills can be learned without overt movement through motor imagery or action observation. Here, we investigated whether sleep spindle activity also supports the consolidation of non-physically learned movements. Forty-five electroencephalographic sleep recordings were collected during a daytime nap after motor sequence learning by physical practice, motor imagery or action observation. Our findings reveal that a temporal cluster-based organization of sleep spindles underlies motor memory consolidation in all groups, albeit with distinct behavioral outcomes. A daytime nap offers an early sleep window promoting the retention of motor skills learned by physical practice and motor imagery, and its generalizability towards the inter-manual transfer of skill after action observation. Findings may further have practical impacts with the development of non-physical rehabilitation interventions for patients having to remaster skills following peripherical or brain injury.

neuroscience↗

bioRxiv2022

Clustering and temporal organization of sleep spindles underlie motor memory consolidation

Sleep benefits motor memory consolidation, which is mediated by sleep spindle activity and associated memory reactivations during non-rapid eye movement (NREM) sleep. However, the particular role of NREM2 and NREM3 sleep spindles and the mechanisms triggering this memory consolidation process remain controversial. Here, simultaneous electroencephalographic and functional magnetic resonance imaging (EEG-fMRI) recordings were collected during night-time sleep following the learning of a motor sequence task. Adopting a time-based clustering approach, we provide evidence that spindles iteratively occur within clustered and temporally organized patterns during both NREM2 and NREM3 sleep. However, the clustering of spindles in trains is related to motor memory consolidation during NREM2 sleep only. Altogether, our findings suggest that spindles clustering and rhythmic occurrence during NREM2 sleep may serve as an intrinsic rhythmic sleep mechanism for the timed reactivation and subsequent consolidation of motor memories, through synchronized oscillatory activity within a subcortical-cortical network involved during learning.

neuroscience↗

bioRxiv2022

Specific targeting of inflammatory osteoclastogenesis by the probiotic yeast S. boulardii CNCM I-745 reduces bone loss in osteoporosis

Bone destruction is a hallmark of chronic inflammation, and bone-resorbing osteoclasts arising under such a condition differ from steady-state ones. However, osteoclast diversity remains poorly explored. Here, we combined transcriptomic profiling, differentiation assays and in vivo analysis in mouse to decipher specific traits for inflammatory and steady state osteoclasts. We identified and validated the pattern-recognition receptors (PRR) TLR2, Dectin-1 and Mincle, all involved in yeast recognition as major regulators of inflammatory osteoclasts. We showed that administration of the yeast probiotic Saccharomyces boulardi CNCM I-745 (Sb) in vivo reduced bone loss in OVX but not sham mice by reducing inflammatory osteoclasts. This beneficial impact of Sb is mediated by the regulation of the inflammatory environment required for the generation of inflammatory osteoclasts. We also showed that Sb derivatives as well as agonists of TLR2, Dectin-1 and Mincle specifically inhibited directly the differentiation of inflammatory but not steady state osteoclasts in vitro. These findings demonstrate a preferential use of the PRR-associated costimulatory differentiation pathway by inflammatory osteoclasts, thus enabling their specific inhibition, which opens new therapeutic perspectives for inflammatory bone loss.

physiology↗

bioRxiv2018

Consolidation alters motor sequence-specific distributed representations

FMRI studies investigating the acquisition of sequential motor skills in humans have revealed learning-related functional reorganizations of the cortico-striatal and cortico-cerebellar motor systems in link with the hippocampus. Yet, the functional significance of these activity level changes is not fully understood as they convey the evolution of both sequence-specific knowledge and unspecific task expertise. Moreover, these changes do not specifically assess the occurrence of learning-related plasticity. To address these issues, we investigated local circuits tuning to sequence-specific information using multivariate distances between patterns evoked by consolidated or newly acquired motor sequences production. Results reveal that representations in dorsolateral striatum, prefrontal and secondary motor cortices are greater when executing consolidated sequences than untrained ones. By contrast, sequence representations in the hippocampus and dorsomedial striatum are less engaged. Our findings show, for the first time in humans, that complementary sequence-specific motor representations evolve distinctively during critical phases of skill acquisition and consolidation.

neuroscience↗