Publications of Eric Salmon
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See detailImpaired explicit self-awareness but preserved behavioral regulation in patients with Alzheimer Disease
Geurten, Marie ULiege; Salmon, Eric ULiege; Bastin, Christine ULiege

in Aging and Mental Health (in press)

Objectives: Impairments of metacognitive skills represent a critical symptom in Alzheimer Disease (AD) because it frequently results in a lack of self-awareness. However, recent findings suggest that ... [more ▼]

Objectives: Impairments of metacognitive skills represent a critical symptom in Alzheimer Disease (AD) because it frequently results in a lack of self-awareness. However, recent findings suggest that, despite an inability to explicitly estimate their own cognitive functioning, patients might demonstrate some implicit recognition of difficulties. In this study, we tested whether a behavioral dissociation between explicit and implicit measures of metacognition can be found in both healthy older controls (n = 20) and AD patients (n = 20). Methods: Our two groups of participants (AD vs. Controls) were asked to complete a forced-choice perceptual identification test and to explicitly rate their confidence in each decision (i.e., explicit measure of metacognition). Moreover, they also had the opportunity to ask for a cue to help them decide if their response was correct (i.e., implicit measure of metacognition). Results: Data revealed that all participants asked for a cue more often after an incorrect response than after a correct response in the forced-choice identification test, indicating a good ability to implicitly introspect on the results of their cognitive operations. On the contrary, only healthy participants displayed metacognitive sensitivity when making explicit confidence judgments. Conclusion: Our findings suggest that implicit metacognition may be less affected than explicit metacognition in Alzheimer’s disease. [less ▲]

Detailed reference viewed: 69 (7 ULiège)
See detailSleep slow waves generation and medial prefrontal microstructure in healthy older individuals
Van Egroo, Maxime ULiege; Chylinski, Daphné ULiege; Narbutas, Justinas ULiege et al

Conference (2020, September 22)

Introduction. Aging is associated with alterations in sleep-wake regulation that have been associated with changes in brain structural integrity. In particular, the ability to generate slow oscillations ... [more ▼]

Introduction. Aging is associated with alterations in sleep-wake regulation that have been associated with changes in brain structural integrity. In particular, the ability to generate slow oscillations during non-rapid eye movement (NREM) sleep decreases as early as in the 5th decade of life, predominantly over frontal regions. While previous investigations have identified macrostructural brain correlates of the age-related decrement in sleep slow waves generation, their relationships with brain tissue microstructure remain poorly understood. Methods. We recorded sleep under electroencephalography in 99 healthy older individuals (mean age = 59.6 ± 5.2 years; 66 women), and we quantified slow waves generation using the overnight cumulated power density in the delta band (0.5-4 Hz) during NREM sleep over the frontal Fz derivation. All participants also underwent 3T magnetic resonance imaging (MRI) scans to investigate tissue myelin content based on quantitative magnetization transfer (MT) saturation mapping, as well as diffusion-based metrics derived from neurite orientation dispersion and density imaging (NODDI) model. A region of interest covering bilateral medial prefrontal cortices was used to extract regional grey matter values. Results. We first observed that MT signal in the medial prefrontal cortex was positively associated with higher neurite orientation dispersion (r = .30, p = .003) and density (r = .22, p = .03), supposedly reflecting preserved microstructural integrity. Crucially, overnight NREM sleep slow waves generation was significantly related to higher prefrontal MT signal (r = .22, p = .03), but not to NODDI metrics (dispersion: r = .02, p = .85; density: r = .09, p = .36). Generalized linear mixed models adjusted for demographics and total sleep time confirmed these relationships, although as a statistical trend for MT signal (F1,93 = 3.64, p = .06). Discussion. Our findings suggest a positive association between tissue myelin content within medial prefrontal grey matter and generation of slow waves during NREM sleep in aging. Preserved prefrontal myelination may facilitate neuronal synchronization through enhanced cortico-cortical connections, resulting in higher power density in the slower frequency band. Given the existing link between sleep characteristics and age-related cognitive decline, these results may have implications for successful cognitive aging. Support: FNRS, ULiège, ARC17/21-09, FEDER, WBI, Clerdent Foundation, Leon Frédéricq Foundation [less ▲]

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See detailAlzheimer’s disease genetic risk and sleep phenotypes: association with more slow-waves and daytime sleepiness
Muto, Vincenzo ULiege; Koshmanova, Ekaterina ULiege; Ghaemmaghami Tabrizi, Pouya ULiege et al

in Sleep (2020)

Study objectives: Sleep disturbances and genetic variants have been identified as risk factors for Alzheimer's disease. Our goal was to assess whether genome-wide polygenic risk scores (PRS) for AD ... [more ▼]

Study objectives: Sleep disturbances and genetic variants have been identified as risk factors for Alzheimer's disease. Our goal was to assess whether genome-wide polygenic risk scores (PRS) for AD associate with sleep phenotypes in young adults, decades before typical AD symptom onset. Methods: We computed whole-genome Polygenic Risk Scores (PRS) for AD and extensively phenotyped sleep under different sleep conditions, including baseline sleep, recovery sleep following sleep deprivation and extended sleep opportunity, in a carefully selected homogenous sample of healthy 363 young men (22.1 y ± 2.7) devoid of sleep and cognitive disorders. Results: AD PRS was associated with more slow wave energy, i.e. the cumulated power in the 0.5-4 Hz EEG band, a marker of sleep need, during habitual sleep and following sleep loss, and potentially with large slow wave sleep rebound following sleep deprivation. Furthermore, higher AD PRS was correlated with higher habitual daytime sleepiness. Conclusions: These results imply that sleep features may be associated with AD liability in young adults, when current AD biomarkers are typically negative, and the notion that quantifying sleep alterations may be useful in assessing the risk for developing AD. [less ▲]

Detailed reference viewed: 61 (7 ULiège)
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See detailFamiliarity for entities as a sensitive marker of antero-lateral entorhinal atrophy in amnestic mild cognitive impairment
Besson, Gabriel ULiege; Simon, Jessica ULiege; Salmon, Eric ULiege et al

in Cortex: A Journal Devoted to the Study of the Nervous System and Behavior (2020), 128

Detailed reference viewed: 41 (9 ULiège)
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See detailExploring with [(18)F]UCB-H the in vivo Variations in SV2A Expression through the Kainic Acid Rat Model of Temporal Lobe Epilepsy.
Serrano Navacerrada, Maria Elisa ULiege; Bahri, Mohamed Ali ULiege; Becker, Guillaume ULiege et al

in Molecular imaging and biology (2020)

PURPOSE: The main purpose of this study was to understand how the positron emission tomography (PET) measure of the synaptic vesicle 2A (SV2A) protein varies in vivo during the development of temporal ... [more ▼]

PURPOSE: The main purpose of this study was to understand how the positron emission tomography (PET) measure of the synaptic vesicle 2A (SV2A) protein varies in vivo during the development of temporal lobe epilepsy (TLE) in the kainic acid rat model. PROCEDURES: Twenty Sprague Dawley male rats were administered with multiple systemic doses of saline (control group, n = 5) or kainic acid (5 mg/kg/injection, epileptic group, n = 15). Both groups were scanned at the four phases of TLE (early, latent, transition, and chronic phase) with the [(18)F]UCB-H PET radiotracer and T2-structural magnetic resonance imaging. At the end of the scans (3 months post-status epilepticus), rats were monitored for 7 days with electroencephalography for the detection of spontaneous electrographic seizures. Finally, the immunofluorescence staining for SV2A expression was performed. RESULTS: Control rats presented a significant increase in [(18)F]UCB-H binding at the last two scans, compared with the first ones (p < 0.001). This increase existed but was lower in epileptic animals, producing significant group differences in all the phases of the disease (p < 0.028). Furthermore, the quantification of the SV2A expression in vivo with the [(18)F]UCB-H radiotracer or ex vivo with immunofluorescence led to equivalent results, with a positive correlation between both. CONCLUSIONS: Even if further studies in humans are required, the ability to detect a progressive decrease in SV2A expression during the development of temporal lobe epilepsy supports the use of [(18)F]UCB-H as a useful tool to differentiate, in vivo, between healthy and epileptic animals along with the development of the epileptic disease. [less ▲]

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See detailAnosognosie: Modèles théoriques et pistes de prise en charge
Bastin, Christine ULiege; Salmon, Eric ULiege

in Revue de Neuropsychologie (2020), 12(1), 26-34

Anosognosia refers to the lack of knowledge, awareness or recognition of a disease or a deficit. In this paper, we review methods to measure anosognosia, the theoretical models that propose explanations ... [more ▼]

Anosognosia refers to the lack of knowledge, awareness or recognition of a disease or a deficit. In this paper, we review methods to measure anosognosia, the theoretical models that propose explanations about its origin and programs to improve awareness of deficits in brain-damaged patients. The presence of anosognosia can be detected by clinical assessments based on observation, by questionnaires comparing patients’ and their relatives’ evaluation of the patients’ everyday life functioning and cognition, or by measures of accuracy of patients’ prediction about performance. There are three classes of theoretical models about anosognosia: neurocognitive models suggest that cognitive deficits (notably executive and mnemonic) associated with damage to certain brain regions (in particular, the prefrontal cortex) lead to a poor apprehension of current functioning, psychological models evoke denial as a defense mechanism against the threat that deficits represent for the person, and biopsychosocial models propose that anosognosia emerges from the interaction between neuropsychologial deficits, psychological defense mechanism and social influences. Because anosognosia can prevent the patient from seeking help and complying with revalidation programs, to improve awareness of deficits is necessary to maximize the benefit of therapeutic programs. A few revalidation programs have tried to improve awareness of deficits by combining various approaches. The most common approaches are the use of feedback during the performance of an everyday life task and metacognitive training focusing on prediction of performance, self-assessement, and self-discovery of strategies to improve performance. While most programs aiming at improving anosognosia were used in single case studies, a few controlled and randomized trials have shown the efficacy of the programs that allowed patients to better detect errors during tasks and to gain autonomy in everyday life. [less ▲]

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See detailHunting down the source: how amnesic patients avoid fluency-based memory errors
Geurten, Marie ULiege; Bastin, Christine ULiege; Salmon, Eric ULiege et al

in Neuropsychology (2020), 34(1), 15-23

Objective: The primary aim of this study was to test whether differences in the ability of amnesic and healthy participants to detect alternative sources of fluency can account for differences observed in ... [more ▼]

Objective: The primary aim of this study was to test whether differences in the ability of amnesic and healthy participants to detect alternative sources of fluency can account for differences observed in the use of fluency as a cue for memory. Method: Patients with severe memory deficits and matched controls were presented with three forced-choice recognition tests. In each test, an external source of fluency was provided by manipulating the perceptual quality of the studied items during the test phase. The detectability of the perceptual manipulation varied in each test (i.e., a 10%, 20%, or 30% contrast reduction were given). Results: The results indicated that all participants were able to rely on fluency when making recognition decisions as long as the perceptual manipulation remained unnoticed. Interestingly, our data also revealed that the level of contrast reduction at which the alternative source is detected differs between healthy controls and amnesic patients. Specifically, patients with amnesia appeared to disqualify fluency as a cue for memory even when the contrast reduction was moderate while healthy participants only disqualified fluency when the contrast reduction was clearly visible. Conclusion: Overall, our results seem to suggest that the ability to use fluency is probably not impaired in amnesia but undergo metacognitive changes resulting in the implementation of explicit or implicit strategies aiming at tracking alternative sources in order to reduce memory errors. [less ▲]

Detailed reference viewed: 71 (3 ULiège)
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See detailFluency-Based Memory Decisions in Alzheimer’s Disease: A Matter of Source Detection?
Geurten, Marie ULiege; Willems, Sylvie ULiege; Salmon, Eric ULiege et al

in Neuropsychology (2020), 34(2), 176-185

Objective: The primary aim of this study was to test whether differences in the ability of patients with Alzheimer Disease (AD) and healthy participants to detect alternative sources of fluency can ... [more ▼]

Objective: The primary aim of this study was to test whether differences in the ability of patients with Alzheimer Disease (AD) and healthy participants to detect alternative sources of fluency can account for differences observed in the use of fluency - i.e., the ease with which information is processed - as a cue for memory. Method: Twenty-two patients with AD and 22 matched controls were presented with three forced-choice visual recognition tests. In each test, an external source of fluency was provided by manipulating the perceptual quality of the items during the test phase. The detectability of the perceptual manipulation varied in each test (i.e., 10%, 20%, or 30% contrast reduction were given). Results: Data indicated that AD patients rely on fluency in a similar extent than older adults as long as they demonstrate intact detection of differences in the perceptual quality of the items. Specifically, it appears that patients’ ability to visually discriminate stimuli differing in terms of their perceptual quality is critical for patients to be able to implement strategies to appropriately use or correctly disqualify fluency during a recognition task. Conclusion: Overall, these findings suggest that the disruption of some basic cognitive processes could prevent AD patients to experience fluency in a similar extent than healthy controls. However, when the ability to detect differences in the perceptual quality of the stimuli was taken into account, patients appeared to be as able as controls to rely on fluency to guide their memory decisions. [less ▲]

Detailed reference viewed: 72 (13 ULiège)
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See detailAge-related differences in the neural correlates of vivid remembering
Folville, Adrien ULiege; Bahri, Mohamed Ali ULiege; Delhaye, Emma ULiege et al

in NeuroImage (2020), 206

When recollecting events, older adults typically report similar memory vividness levels as young adults, while they actually retrieve fewer episodic details. This suggests that young and older adults use ... [more ▼]

When recollecting events, older adults typically report similar memory vividness levels as young adults, while they actually retrieve fewer episodic details. This suggests that young and older adults use episodic details differently to calibrate their vividness judgements. Capitalizing on the idea that remembering reactivates brain regions that initially processed details at encoding, the current fMRI study sought to examine these age-related changes in the basis of vivid recollection. At encoding, young and older adults saw pictures associated with labels and these labels were then used as retrieval cues for recalling the associated pictures and making memory vividness judgments. Results showed that highly vivid memories were associated with greater activity in the precuneus in young than older adults. Furthermore, the direct comparison between encoding and retrieval patterns of activity using Representational Similarity Analyses revealed stronger item-specific reactivation in the posterior cingulate/retrosplenial cortex in young than older adults. Taken together, these results provide new evidence that aging is associated with reduced reinstatement of activity in brain regions that processed the encoding of complex stimuli, but older individuals judge these impoverished memory representations as subjectively vivid. [less ▲]

Detailed reference viewed: 51 (11 ULiège)
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See detailIn vivo imaging of synaptic loss in Alzheimer’s disease with [18F]UCB-H Positron Emission Tomography
Bastin, Christine ULiege; Bahri, Mohamed Ali ULiege; Meyer, François ULiege et al

in European Journal of Nuclear Medicine and Molecular Imaging (2020), 47(2), 390-402

Detailed reference viewed: 108 (16 ULiège)
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See detailExploring scoring methods for research studies: Accuracy and variability of visual and automated sleep scoring
Berthomier, Christian; Muto, Vincenzo ULiege; Schmidt, Christina ULiege et al

in Journal of Sleep Research (2020)

Sleep studies face new challenges in terms of data, objectives and metrics. This requires reappraising the adequacy of existing analysis methods, including scoring methods. Visual and automatic sleep ... [more ▼]

Sleep studies face new challenges in terms of data, objectives and metrics. This requires reappraising the adequacy of existing analysis methods, including scoring methods. Visual and automatic sleep scoring of healthy individuals were compared in terms of reliability (i.e., accuracy and stability) to find a scoring method capable of giving access to the actual data variability without adding exogenous variability. A first dataset (DS1, four recordings) scored by six experts plus an autoscoring al-gorithm was used to characterize inter-scoring variability. A second dataset (DS2, 88 recordings) scored a few weeks later was used to explore intra-expert variabil-ity. Percentage agreements and Conger's kappa were derived from epoch-by-epoch comparisons on pairwise and consensus scorings. On DS1 the number of epochs of agreement decreased when the number of experts increased, ranging from 86% (pairwise) to 69% (all experts). Adding autoscoring to visual scorings changed the kappa value from 0.81 to 0.79. Agreement between expert consensus and autoscor-ing was 93%. On DS2 the hypothesis of intra-expert variability was supported by a systematic decrease in kappa scores between autoscoring used as reference and each single expert between datasets (.75–.70). Although visual scoring induces inter- and intra-expert variability, autoscoring methods can cope with intra-scorer variabil-ity, making them a sensible option to reduce exogenous variability and give access to the endogenous variability in the data. [less ▲]

Detailed reference viewed: 59 (14 ULiège)
See detailAlzheimer s disease genetic risk and sleep phenotypes: association with more slow-waves and daytime sleepiness
Muto, Vincenzo ULiege; Koshmanova, Ekaterina ULiege; Ghaemmaghami, Pouya  et al

E-print/Working paper (2020)

Detailed reference viewed: 60 (15 ULiège)
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See detailIndividual Brain Charting dataset extension, second release of high-resolution fMRI data for cognitive mapping.
Pinho, Ana Luísa; Amadon, Alexis; Gauthier, Baptiste et al

in Scientific Data (2020), 7(1), 353

We present an extension of the Individual Brain Charting dataset -a high spatial-resolution, multi-task, functional Magnetic Resonance Imaging dataset, intended to support the investigation on the ... [more ▼]

We present an extension of the Individual Brain Charting dataset -a high spatial-resolution, multi-task, functional Magnetic Resonance Imaging dataset, intended to support the investigation on the functional principles governing cognition in the human brain. The concomitant data acquisition from the same 12 participants, in the same environment, allows to obtain in the long run finer cognitive topographies, free from inter-subject and inter-site variability. This second release provides more data from psychological domains present in the first release, and also yields data featuring new ones. It includes tasks on e.g. mental time travel, reward, theory-of-mind, pain, numerosity, self-reference effect and speech recognition. In total, 13 tasks with 86 contrasts were added to the dataset and 63 new components were included in the cognitive description of the ensuing contrasts. As the dataset becomes larger, the collection of the corresponding topographies becomes more comprehensive, leading to better brain-atlasing frameworks. This dataset is an open-access facility; raw data and derivatives are publicly available in neuroimaging repositories. [less ▲]

Detailed reference viewed: 23 (5 ULiège)
See detailEffort as a sensitive variable of wakefulness extension and its impact on cognitive performance
Mouraux, Charlotte; Van Egroo, Maxime ULiege; Chylinski, Daphné ULiege et al

Conference (2019, November)

Detailed reference viewed: 45 (10 ULiège)