Julie Carrier

Université de Montréal | UdeM · Department of Psychology

Non-rapid eye movement (NREM) sleep is characterized by the interaction of multiple coupled oscillations essential for various functions such as memory consolidation, alongside a pervasive and dynamic arrhythmic 1/f scale-free background that may also contribute to these functions. Although recent spectral parametrization methods such as FOOOF (Fit...

Clinical and neuroanatomical correlates of daytime sleepiness in Parkinson’s disease (PD) remain inconsistent in the literature. Two studies were conducted here. The first evaluated the interrelation between non-motor and motor symptoms, using a principal component analysis, associated with daytime sleepiness in PD. The second identified the neuroa...

This study aimed to progress the understanding of idiopathic hypersomnia (IH) by assessing the moderating influence of individual characteristics, such as age, sex, and body mass index (BMI) on sleep architecture. In this retrospective study, 76 IH participants (38.1 ± 11.3 years; 40 women) underwent a clinical interview, an in-laboratory polysomno...

Patients with idiopathic hypersomnia frequently report having unrefreshing naps. However, whether they have abnormal sleep architecture during naps that may explain their unrefreshing aspect is unknown. We compared sleep architecture during short daytime naps in patients with idiopathic hypersomnia reporting unrefreshing and refreshing naps. One‐hu...

Sleep slow waves are the hallmark of deeper non-rapid eye movement sleep. It is generally assumed that gray matter properties predict slow-wave density, morphology, and spectral power in healthy adults. Here, we tested the association between gray matter volume (GMV) and slow-wave characteristics in 27 patients with moderate-to-severe traumatic bra...

Caffeine is the most widely consumed psychoactive stimulant worldwide. Yet important gaps persist in understanding its effects on the brain, especially during sleep. We analyzed sleep EEG in 40 subjects, contrasting 200mg of caffeine against a placebo condition, utilizing inferential statistics and machine learning. We found that caffeine ingestion...

INTRODUCTION The limbic system is critical for memory function and degenerates early in the Alzheimer's disease continuum. Whether obstructive sleep apnea (OSA) is associated with alterations in the limbic white matter tracts remains understudied. METHODS Polysomnography, neurocognitive assessment, and brain magnetic resonance imaging (MRI) were p...

Introduction Abnormal cortical synchronization during sleep could affect the restorative function of sleep and consequently, increase daytime sleepiness. Slow wave (SW) density and characteristics provide a unique window of how cortical neurons synchronize during non-rapid eye movement (NREM) sleep. Here, we aimed at verifying whether NREM sleep SW...

Study Objectives Apolipoprotein E ɛ4 (APOE4) is the strongest genetic risk factor for Alzheimer’s disease (AD). In addition, APOE4 carriers may exhibit sleep disturbances, but conflicting results have been reported, such that there is no clear consensus regarding which aspects of sleep are impacted. Our objective was to compare objective sleep arch...

While commonly treated as a uniform state in practice, rapid eye movement sleep contains two distinct microstructures—phasic (presence of rapid eye movement) and tonic (no rapid eye movement). This study aims to identify technical challenges during rapid eye movement sleep microstructure visual classification in patients with rapid eye movement sle...

Study Objectives Idiopathic/isolated REM-sleep behavior disorder (iRBD) often precedes the onset of synucleinopathies. Here, we investigated whether baseline resting-state EEG advanced spectral power and functional connectivity differ between iRBD patients who converted towards a synucleinopathy at follow-up and those who did not. Methods Eighty-o...

The present study evaluates the efficacy of behavioural therapy adapted for shift work disorder with a randomised control design in a healthcare population. Forty‐three night shift workers (m. age: 34 years; 77% women) experiencing shift work disorder were randomised to either the behavioural therapy for shift work disorder (BT‐SWD) or a waiting‐li...

Study objectives: Sleep is required for successful memory consolidation. Sleep spindles, bursts of oscillatory activity occurring during non-REM sleep, are known to be crucial for this process and, recently, it has been proposed that the temporal organization of spindles into clusters might additionally play a role in memory consolidation. In Park...

Memory consolidation can be enhanced during sleep using targeted memory reactivation (TMR) and closed-loop (CL) acoustic stimulation on the up-phase of slow oscillations (SOs). Here, we tested whether applying TMR at specific phases of the SOs (up vs. down vs. no reactivation) could influence the behavioral and neural correlates of motor memory con...

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 unclear. Here, simultaneous electroencephalograph...

Background Increasing evidence suggests a link between sleep and late‐life Alzheimer disease’s (AD) pathology. We investigated whether sleep degradation might be accompanied by faster AD pathology accumulation and/or whether early AD pathologic changes might be accompanied by sleep changes before the onset of cognitive symptoms. Method We investig...

Background Sleep disruption is common in older adults, and emerging evidence suggests that differences in sleep whether measured by electroencephalography (EEG) or actigraphy, may be associated with clinical cognitive outcomes, and with specific dementia‐associated pathologies. However, whether EEG and actigraphic sleep features may predict cogniti...

Background Increasing evidence suggests a link between sleep and late‐life Alzheimer disease’s (AD) pathology. We investigated whether sleep degradation might be accompanied by faster AD pathology accumulation and/or whether early AD pathologic changes might be accompanied by sleep changes before the onset of cognitive symptoms. Method We investig...

Sleep is required for successful memory consolidation. Sleep spindles, bursts of oscillatory activity occurring during non-REM sleep, are known to be crucial for this process and, recently, it has been proposed that the temporal organization of spindles into clusters might additionally play a role in memory consolidation. In Parkinson’s disease, sp...

Electroencephalographic sleep stage transitions and altered first REM sleep period transitions have been identified as biomarkers of type 1 narcolepsy in adults, but not in children. Studies on memory complaints in narcolepsy have not yet investigated sleep-dependent memory consolidation. We aimed to explore stage transitions; more specifically alt...

Background: Clinical and neuroanatomical correlates of daytime sleepiness in Parkinson’s disease remain inconsistent in the literature. Objectives: Two studies were conducted. The first study evaluated the interrelation between non-motor and motor symptoms associated with daytime sleepiness in Parkinson’s disease. The second study identified the ne...

Targeted memory reactivation (TMR) during sleep enhances memory consolidation in young adults by modulating electrophysiological markers of neuroplasticity. Interestingly, older adults exhibit deficits in motor memory consolidation, an impairment that has been linked to age‐related degradations in the same sleep features sensitive to TMR. We hypoth...

Background Rapid-eye movement (REM) sleep highly depends on the activity of cholinergic basal forebrain (BF) neurons and is reduced in Alzheimer’s disease. Here, we investigated the associations between the volume of BF nuclei and REM sleep characteristics, and the impact of cognitive status on these links, in late middle-aged and older participant...

Study objectives: Unrefreshing naps are supportive clinical features of idiopathic hypersomnia (IH) and are reported by more than 50% of IH patients. They are, however, not mandatory for the diagnosis, and their pathophysiological nature is not understood. This study aimed at verifying whether IH patients with and without unrefreshing naps constit...

Introduction Obstructive sleep apnea (OSA) is increasingly recognized as a risk factor for cognitive decline, and has been associated with structural brain alterations in regions relevant to memory processes and Alzheimer’s disease. However, it is unclear whether OSA is associated with disrupted functional connectivity (FC) patterns between these r...

Background Obstructive sleep apnea (OSA) is associated with risk of cognitive decline in older adults. Our group previously observed that more severe OSA was associated with lower functional connectivity between the hippocampus and multiple regions of the default‐mode network (DMN) and the limbic system. However, whether these lower functional conn...

Objectives: 1) Determine the best exercise modality to improve sleep quality and sleep architecture in people with Parkinson Disease (PD); 2) Investigate whether exercise-induced improvements in sleep mediate enhancements in motor and cognitive function as well as other non-motor symptoms of PD; 3) Explore if changes in systemic inflammation after...

Introduction: Animal studies have demonstrated that physical exercise can protect memory from the effects of sleep deprivation (SD). We examined whether having a high cardio-respiratory fitness (VO2peak) is associated with an enhanced capacity to encode episodic memory after one night of SD. Methods: Twenty-nine healthy young participants were a...

Study objectives: Pre- and early adolescence are believed to constitute periods of important age-related changes in sleep. However, much of the research on these presumed developmental changes has used cross-sectional data or subjective measures of sleep, limiting the quality of the evidence. Additionally, little is known about the development of...

Meta-analysis of whole genome sequencing/whole exome sequencing (WGS/WES) studies provides an attractive solution to the problem of collecting large sample sizes for discovering rare variants associated with complex phenotypes. Existing rare variant meta-analysis approaches are not scalable to biobank-scale WGS data. Here we present MetaSTAAR, a po...

The basal forebrain cholinergic system (BFCS) degenerates in Alzheimer’s disease (AD) before the onset of dementia. Interestingly, rapid‐eye movement (REM) sleep is highly dependent on cholinergic activity. In AD patients, REM sleep duration is reduced but the underlying brain mechanisms are still unclear. Our objective was to investigate the assoc...

Studies investigating the possible links between obstructive sleep apnea (OSA) and cognitive dysfunction have yet led to heterogenous results. Individual characteristics, such as sex and age, could moderate this association and explain part of this heterogeneity. Here, we characterized the sex‐ and age‐specific association between OSA risk and cogn...

Neuroimaging studies in obstructive sleep apnea (OSA) have found both gray matter atrophy and hypertrophy in medial temporal lobe subregions, the latter probably reflecting edema. Whether and how these changes progress over time when OSA is treated or untreated remains unclear. Here, we investigated gray matter volume changes in medial temporal lob...

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 electroencephal...

Targeted memory reactivation (TMR) during post-learning sleep enhances memory consolidation in young adults by modulating electrophysiological markers of plasticity (i.e., slow waves (SW) and slow/sigma oscillation coupling). Interestingly, older adults are known to exhibit deficits in motor memory consolidation, an impairment that has been linked...

Medial temporal structures, namely the hippocampus, the entorhinal cortex and the parahippocampal gyrus, are particularly vulnerable to Alzheimer’s disease and hypoxemia. Here, we tested the associations between obstructive sleep apnea (OSA) severity and medial temporal lobe volumes in 114 participants aged 55–86 years (35 % women). We also investi...

The sleep slow wave (SW) transition between negative and positive phases is thought to mirror synaptic strength and likely depends on brain health. This transition shows significant age-related changes but has not been investigated in pathological aging. The present study aimed at comparing the transition speed and other characteristics of SW betwe...

Large-scale whole-genome sequencing studies have enabled analysis of noncoding rare-variant (RV) associations with complex human diseases and traits. Variant-set analysis is a powerful approach to study RV association. However, existing methods have limited ability in analyzing the noncoding genome. We propose a computationally efficient and robust...

Scientists in sleep and circadian rhythms, public health experts, healthcare providers, partners, and stakeholders convened in 2020 for a 2-day meeting organized by the Canadian Sleep and Circadian Network to develop a national strategy for the integration of sleep and circadian rhythms into public health and policies in Canada. The objective of th...

Objective To estimate the years of life gained when meeting the sleep duration recommendations across the adult lifespan. Methods Three pieces of information were used to estimate and compare life expectancy at each age of adult life among Canadian adults who did and did not meet sleep duration recommendations: (i) the prevalence of self-reported...

Integrating genetic information with metabolomics has provided new insights into genes affecting human metabolism. However, gene-metabolite integration has been primarily studied in individuals of European Ancestry, limiting the opportunity to leverage genomic diversity for discovery. In addition, these analyses have principally involved known meta...

Study Objectives To examine the longitudinal association between probable insomnia status and both subjective and objective memory decline in middle-aged and older adults. Methods 26,363 participants, ≥45 years, completed baseline and follow-up (3 years after baseline) self-reported evaluations of sleep and memory, and neuropsychological testing i...

Study objectives The ability to generate slow waves (SW) during non-rapid eye movement (NREM) sleep decreases as early as the 5 th decade of life, predominantly over frontal regions. This decrease may concern prominently SW characterised by a fast switch from hyperpolarised to depolarised, or down-to-up, state. Yet, the relationship between these f...

Targeted memory reactivation (TMR) during post-learning sleep is known to enhance motor memory consolidation but the underlying neurophysiological processes remain unclear. Here, we confirm the beneficial effect of auditory TMR on motor performance. At the neural level, TMR enhanced slow wave (SW) characteristics. Additionally, greater TMR-related...

Sleep alteration is a hallmark of ageing and emerges as a risk factor for Alzheimer's disease (AD). While the fine-tuned coalescence of sleep microstructure elements may influence age-related cognitive trajectories, its association with AD processes is not fully established. Here, we investigated whether the coupling of spindles and slow waves is a...

Study Objectives Traumatic brain injuries (TBI) cause persistent cerebral damage and cognitive deficits. Because sleep may be a critical factor to brain recovery, we characterized the sleep of patients with traumatic brain injury from early hospitalization to years post-injury, and explored the hypothesis that better sleep during hospitalization pr...

Sleep spindles (SS) are crucial to brain functions like memory and learning. SS characteristics result from the propagation of nerve impulses along white matter (WM) projections underlying an intricate loop between the thalamus and the cortex. SS amplitude and density have been associated with WM diffusion microarchitecture but physiological mechan...

Background: The present study investigated whether sleep deprivation affects attention capture in young and older adults using event-related potentials (ERPs). Methods: Eleven young adults (20-30 y) and nine older adults (60-70 y) were tested following both normal sleep (NS) and total sleep deprivation (TSD). ERPs were recorded during an auditor...

Objective To provide estimates of the health care and productivity costs associated with insufficient sleep duration (<7 hours per night) in Canadian adults. Methods A prevalence-based approach was used to estimate the economic costs associated with insufficient sleep duration. Estimates relied on 3 pieces of information: (1) the relative risks of...

Determining the prevalence and characteristics of individuals susceptible to present with obstructive sleep apnea (OSA) is essential for developing targeted and efficient prevention and screening strategies. We included 27,210 participants aged ≥45 years old (50.3% women) from the Canadian Longitudinal Study on Aging. Using the STOP questionnaire c...

Sleep alteration is a hallmark of ageing and emerges as a risk factor for Alzheimer's disease (AD). While the fine-tuned coalescence of sleep microstructure elements may influence age-related cognitive trajectories, its association with AD processes is not fully established. Here, we investigated whether the coupling of spindles and slow waves is a...

Analyses of data from genome-wide association studies on unrelated individuals have shown that, for human traits and diseases, approximately one-third to two-thirds of heritability is captured by common SNPs. However, it is not known whether the remaining heritability is due to the imperfect tagging of causal variants by common SNPs, in particular...

Background The association between obstructive sleep apnea and cognitive functioning is not yet fully understood and could be influenced by factors such as sex, age and systemic inflammation. We determined the sex- and age-specific association between obstructive sleep apnea risk and cognitive performance, and the influence of systemic inflammation...

ROIG, M., J. CRISTINI, Z. PARWANTA, B. AYOTTE, L. RODRIGUES, B. DE LAS HERAS, J-F. NEPVEU, R. HUBER, J. CARRIER, S. STEIB, S.D. YOUNGSTEDT, and D.L. WRIGHT. Exercising the sleepy-ing brain: exercise, sleep, and sleep loss on memory. Exerc. Sport Sci. Rev., Vol. 50, No. 1, pp. 38–48, 2022. We examine the novel hypothesis that physical exercise and s...

Résumé Introduction Les troubles du sommeil sont fréquents chez les patients avec un trouble neurocognitif. Leur diagnostic et prise en charge chez ces patients peut s’avérer complexe en pratique clinique. Méthode Cette revue narrative offre une approche systématique basée sur les données probantes afin de diagnostiquer et traiter les troubles du...

Background Recent studies have suggested that obstructive sleep apnea (OSA) could be a modifiable risk factor for dementia. Consequently, efforts have been made to better understand the role of OSA on brain structure integrity, but results between studies are inconsistent. Discrepancies could be partly due to moderating factors (e.g., sex) or compl...

Background Our research team has demonstrated that quantitative electroencephalography (qEEG) slowing during rapid‐eye movement (REM) sleep is a more powerful tool to discriminate patients with mild cognitive impairment (MCI) or Alzheimer Disease (AD) from healthy controls than waking EEG. Cortical activation during REM sleep highly depends on the...

Background Growing evidence supports associations between cognitive impairment and obstructive sleep apnea (OSA). Our study aimed at determining the age and sex‐specific, independent relationship between risk of having OSA and cognitive performance, and the influence of systemic inflammation on this relationship. Method Our sample included 25,712...

In older adults, motor sequence learning (MSL) is largely intact. However, consolidation of newly learned motor sequences is impaired compared to younger adults, and there is evidence that brain areas supporting enhanced consolidation via sleep degrade with age. It is known that brain activity in hippocampal–cortical–striatal areas is important for...

Background Rapid-eye-movement sleep behavior disorder (RBD) is a major risk factor for Parkinson’s disease and dementia with Lewy bodies. More than a third of RBD patients have mild cognitive impairment (MCI), but their specific structural brain alterations remain poorly understood. Objective This study aimed to investigate the local deformation a...

Fine-mapping to plausible causal variation may be more effective in multi-ancestry cohorts, particularly in the MHC, which has population-specific structure. To enable such studies, we constructed a large (n = 21,546) HLA reference panel spanning five global populations based on whole-genome sequences. Despite population-specific long-range haploty...

We examine the novel hypothesis that physical exercise and sleep have synergistic effects on memory. Exercise can trigger mechanisms that can create an optimal brain state during sleep to facilitate memory processing. The possibility that exercise could counteract the deleterious effects of sleep deprivation on memory by protecting neuroplasticity...

Background Idiopathic rapid eye movement sleep behavior disorder (iRBD) is a major risk factor for synucleinopathies, and patients often present with clinical signs and morphological brain changes. However, there is an important heterogeneity in the presentation and progression of these alterations, and the brain regions that are more vulnerable to...

Targeted memory reactivation (TMR) during post-learning sleep is known to enhance motor memory consolidation but the underlying neurophysiological processes remain unclear. Here, we confirm the beneficial effect of auditory TMR on motor performance. At the neural level, TMR enhanced slow waves (SW) characteristics. Additionally, greater TMR-related...

During the early days of the pandemic and in the context of a seemingly unknown global threat, several potential major sleep disruptors were identified by sleep researchers and practitioners across the globe. The COVID-19 pandemic combined several features that, individually, had been shown to negatively affect sleep health in the general populatio...

Sleep slow waves are studied for their role in brain plasticity, homeostatic regulation and their changes during aging. Here, we address the possibility that two types of slow waves co-exist in humans. Thirty young and 29 older adults underwent a night of polysomnographic recordings. Using the Transition frequency, slow waves with a slow transition...

Sleep stage scoring can lead to important inter-expert variability. Although likely, whether this issue is amplified in older populations, which show alterations of sleep electrophysiology, has not been thoroughly assessed. Algorithms for automatic sleep stage scoring may appear ideal to eliminate inter-expert variability. Yet, variability between...