Arnaud Saj

Arnaud Saj
Université de Montréal | UdeM · Department of Psychology

PhD

About

126
Publications
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Publications

Publications (126)
Article
Full-text available
There is growing evidence that both the basal ganglia and the cerebellum play functional roles in emotion processing, either directly or indirectly, through their connections with cortical and subcortical structures. However, the lateralization of this complex processing in emotion recognition remains unclear. To address this issue, we investigated...
Preprint
Full-text available
The effectiveness of EEG-neurofeedback (EEG-NFB) in modulating cognition has been the subject of much research for several years, particularly in relation to attentional functions in healthy subjects and those with attentional deficits. However, its effectiveness on sports performance remains poorly studied and its use is not widely practised among...
Article
Purpose: . The concept of lockdown in relation to COVID-19 is thought to have an indirect impact on the quality of life and well-being of the elderly due to its consequences on the physical, psychological, and cognitive health of individuals. However, previous published studies on this subject are limited in terms of methodological approach used,...
Article
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Several cortical and sub-cortical regions in the right hemisphere, particularly in the parietal and frontal lobes, but also in the temporal lobe and thalamus, are part of neural networks critically implicated in spatial and attentional functions. Damage to different sites within these networks can cause hemispatial neglect. The aim of this study wa...
Article
Full-text available
Stroke frequently produces attentional dysfunctions including symptoms of hemispatial neglect, which is characterized by a breakdown of awareness for the contralesional hemispace. Recent studies with functional MRI (fMRI) suggest that hemineglect patients display abnormal intra- and interhemispheric functional connectivity. However, since stroke is...
Chapter
1. Introduction Les observations cliniques mettent en évidence la présence d’un grand nombre de difficultés au niveau des compétences visuospatiales chez les enfants. Ces difficultés peuvent se manifester au travers d’une grande variété d’activités, telles que la manipulation d’objet, le dessin, la construction de puzzle, l’écriture, l’organisatio...
Article
Full-text available
Spatial neglect is a neuropsychological syndrome characterized by a failure to orient, perceive, and act toward the contralesional side of the space after brain injury. Neglect is one of the most frequent and disabling neuropsychological syndromes following right-hemisphere damage, often persisting in the chronic phase and responsible for a poor fu...
Article
Full-text available
In recent years, there has been increasing evidence of cerebellar involvement in emotion processing. Difficulties in the recognition of emotion from voices (i.e.., emotional prosody) have been observed following cerebellar stroke. However, the interplay between sensory and higher-order cognitive dysfunction in these deficits, as well as possible he...
Article
Full-text available
Unilateral spatial neglect is a neuropsychological syndrome commonly observed after stroke and defined by the inability to attend or respond to contralesional stimuli. Typically, symptoms are assessed using clinical tests that rely upon visual/perceptual abilities. However, neglect may affect high-level representations controlling attention in othe...
Article
Background In this study, we examined whether egocentric representation of space is impaired in chronic unilateral vestibulopathies. The objective was to test current theories attributing a predominant role to vestibular afferents in spatial cognition and to assess whether representational neglect signs are common sign in peripheral vestibular loss...
Article
Full-text available
Navigating toward a goal and mentally comparing distances and directions to landmarks are processes requiring reading information off the memorized representation of the environment, that is, the cognitive map. Brain structures in the medial temporal lobe, in particular, are known to be involved in the learning, storage, and retrieval of cognitive...
Chapter
Full-text available
1. Introduction Des troubles visuo-perceptifs et visuo-spatiaux chez l’enfant peuvent se manifester dans de nombreuses activités, telles que la reconnaissance d’images, la construction de puzzles, le dessin, l’écriture, l’orientation dans l’environnement quotidien. Cependant, l’interprétation de ces difficultés est complexe pour plusieurs raisons....
Article
Full-text available
Neuroimaging studies suggest that understanding emotions in others engages brain regions partially common to those associated with more general cognitive Theory-of-Mind (ToM) functions allowing us to infer people's beliefs or intentions. However, neuropsychological studies on brain-damaged patients reveal dissociations between the ability to unders...
Article
Background: Recently, a study using the subjective straight-ahead task showed that individuals with Williams syndrome (WS) present a bias in the representation of body perception. The aim of the present study is to examine the horizontal midline body representation in WS participants using the bisection line task, which is an important benchmark f...
Presentation
Introduction La stabilité posturale diminuant avec l’âge, les personnes âgées ont de plus en plus de difficulté à réaliser deux tâches simultanément. En effet, l’augmentation du contrôle moteur et sensoriel pour le maintien de l’équilibre réduit les capacités cognitives, notamment attentionnelles lors de la réalisation de la seconde tâche (Shumway-...
Article
Full-text available
Introduction Plusieurs études suggèrent que les interventions multimodales, combinant la remédiation cognitive, l’entraînement cognitif et l’exercice physique, peuvent avoir un impact positif sur les performances cognitives et le bien-être. Toutefois, ces interventions, souvent peu écologiques, peuvent engendrer un stress important. Le présent proj...
Conference Paper
Introduction L’évaluation en milieu réel ou écologique momentanée (ÉMÉM) permet d’obtenir des informations uniques et différentes de l’évaluation traditionnelle en milieu clinique ou en laboratoire. Les musées sont des environnements riches pour la compréhension du comportement humain. Leurs vastes espaces requièrent de bonnes capacités de mobilité...
Article
Our perception of space is based on the integration of signals from vestibular, visual, and somatosensory systems. These sensory modalities allow awareness of the displacements and positions of our body and body parts, as well as the locations of objects in extra-personal space. Brain lesions can produce severe deficits in the representation of per...
Article
Full-text available
It is debated whether the amygdala is critical for the emotional modulation of attention. While some studies show reduced attentional benefits for emotional stimuli in amygdala-damaged patients, others report preserved emotional effects. Various factors may account for these discrepant findings, including the temporal onset of the lesion, the compl...
Article
Spatial remapping implies the updating and maintaining of the spatial position of objects in successive visual images across time, despite their displacement on the retina due to eye movements. In the parietal cortex, the representation of spatial locations appears to be partly centered on gaze direction, and thus modulated by current eye-gaze posi...
Article
Background: Most stroke patients exhibit low levels of walking activity, a key component of secondary stroke prevention. The predictors of walking activity may be multifactorial and are thus far partially understood. We aimed to study the neuroanatomic correlates of low levels of daily walking activity following hemispheric stroke. Methods: In t...
Article
BACKGROUND: Gait impairment is observed in early stages of dementia, such as mild cognitive impairment (MCI), and is associated with morphological brain volume changes like atrophy. OBJECTIVE: This study aims to characterize the brain's grey matter (GM) volume covariance associated with gait speed in patients with amnestic mild cognitive impairmen...
Article
Prism adaptation (PA) is one of the few rehabilitation techniques for spatial neglect that directly targets physiological mechanisms underlying space representation, but its efficacy and neural mechanisms remain unresolved. Using PA and fMRI in patients with spatial neglect after an acute right-hemispheric stroke, we previously observed post-PA inc...
Article
Remapping is a process that updates visual information in internal spatial representations across eye movements, allowing for stable perception of the environment. Previous work has demonstrated visual remapping activity in parietal cortex during saccades, but it remains unclear whether remapping is triggered by overt saccades only (or by attention...
Preprint
Full-text available
Stroke frequently produces attentional dysfunctions including symptoms of hemispatial neglect, which is characterized by a breakdown of awareness for the contralesional hemispace. Recent studies with functional MRI (fMRI) suggest that hemineglect patients display abnormal intra- and inter- hemispheric functional connectivity. However, since stroke...
Article
Full-text available
Vertical representation is central to posture control, as well as to spatial perception and navigation. This representation has been studied for a long time in patients with vestibular disorders and more recently in patients with hemispheric damage, in particular in those with right lesions causing spatial or postural deficits. The aim of the study...
Article
Full-text available
Au cours du 3ème Congrès National de Neuropsychologie Clinique (CNNC) a eu lieu en France la première rencontre entre les représentants des associations de psychologues spécialisés en neuropsychologie issus de quatre territoires francophones : la Belgique, la France, la province du Québec et la Suisse. Ces associations sont impliquées dans la promo...
Article
Objective: Unilateral spatial neglect is a multi-faceted syndrome that arises from brain lesions, typically in the right hemisphere, and is characterized by the failure to attend or respond to stimuli in contralesional space. Here, we expand on the proposal that one deficit contributing to the diverse symptoms in neglect involves spatial remapping...
Article
Objective: Recent studies suggest that motivational cues such as rewards may be a powerful determinant of attentional selection, both in healthy subjects and in brain-damaged patients suffering from neglect. However, the exact brain mechanisms underlying these effects and their relation to other well-known attentional systems are still poorly know...
Article
Introduction/Background Unilateral spatial neglect (USN) is a neuropsychological syndrome in which patients fail to pay attention to and represent the contralesional part of the space. Standard assessment of USN is carried out with paper-and-pencil tests, which do not capture the full range of deficits (i.e., not sensitive enough; no evaluation of...
Article
Spatial neglect is a complex neuropsychological disorder, in which patients fail to detect and respond to contralesional stimuli. Recent studies suggest that these symptoms may reflect a combination of different component deficits, associated with different lesion substrates. Thus, damage to right lateral prefrontal and inferior parietal regions pr...
Article
Full-text available
Objective: Apathy-the most common behavioral disturbance in idiopathic normal pressure hydrocephalus (iNPH)-is associated with poor gait, but the role of apathy on gait improvement after cerebrospinal fluid (CSF) tapping has not been studied yet. This study aims to compare gait improvement after CSF tapping in iNPH patients with and without apathy...
Article
Full-text available
Introduction Internal representation of the body's sagittal plane is an important benchmark for an egocentric frame of reference, but little is known about its developmental trajectory. The aim of the present study was to assess this internal body representation with the subjective straight ahead task. Material and methods A total of 131 school-ag...
Article
Full-text available
Introduction Le syndrome vestibulaire unilatéral s’exprime par un ensemble de symptômes oculomoteurs, posturaux et perceptifs. Plus récemment, le rôle du système vestibulaire a été mis en évidence dans la représentation spatiale du corps. L’objectif de cette étude a été d’évaluer les conséquences immédiates et le décours postlésionnel de la perte v...
Article
Objectives Idiopathic normal pressure hydrocephalus (iNPH) is very prevalent in aging, underdiagnosed, and represents a rare cause of reversible neurological condition. The clinical triad of iNPH − gait, cognitive and urinary symptoms – and its neuroradiological features (i.e. ventriculomegaly) are not specific and found a various neurodegenerative...
Article
Full-text available
Despite recent attempts to use electroencephalogram (EEG) neurofeedback (NFB) as a tool for rehabilitation of motor stroke, its potential for improving neurological impairments of attention—such as visuospatial neglect—remains underexplored. It is also unclear to what extent changes in cortical oscillations contribute to the pathophysiology of negl...
Article
Hemineglect is common after right parietal stroke, characterised by impaired awareness for stimuli in left visual space, with suppressed neural activity in the right visual cortex due to losses in top-down attention signals. Here we sought to assess whether hemineglect patients are able to up-regulate their right visual cortex activity using audito...
Article
Full-text available
Most studies on sensory extinction have focused on selected patients with subacute and chronic right hemisphere lesions. In studies conducted on acute stroke patients, risk factors and time course were not evaluated. Our aim was to determine the prevalence, risk factors, and time course of sensory extinction in the acute stroke setting. Consecutive...
Article
Background: Individuals with Williams Syndrome (WS) are known to have particular difficulties when performing visuo-spatial tasks, which could be related to their difficulties in using a specific reference system to determine spatial relations. The aim of the present study was to assess the internal representation of the body's sagittal plane, whi...
Article
Apathy represents the most common behavioral disturbance in patients with suspicion of idiopathic normal pressure hydrocephalus (iNPH) and has a major impact on quality of life. However, its impact on gait –the hallmark motor disturbance of iNPH - has never been studied yet. This study aims to evaluate the impact of apathy on higher level of gait c...
Article
Full-text available
Introduction Les personnes atteintes du syndrome de Williams (WS) sont connues pour avoir des difficultés dans les tâches visuo-spatiales qui exigent l’utilisation des cadres de référence égocentré et/ou allocentré. Le droit devant subjectif (DDS) permet de mesurer la référence de trame égocentrique, en fonction du lobe pariétal. L’objectif de cett...
Article
Full-text available
Introduction La perception de l’orientation corporelle (axe Z) résulte de l’intégration d’informations issues des systèmes sensoriels somesthésique, vestibulaire et visuel. Nous avons montré récemment qu’après une lésion gauche du tronc cérébral (LTC-G) les patients présentent une représentation altérée de l’orientation corporelle dans le plan hori...
Article
Aim: The study aims to describe the epidemiology and the neural correlates of peripersonal visuospatial neglect (PVN) in patients admitted to the Geneva Stroke Unit for an acute stroke or a transient ischemic attack (TIA). Methods: Eligible subjects were tested for PVN using both the Ota's discriminative cancellation task and a line bisection ta...
Article
Full-text available
Aim: The study aims to describe the epidemiology and the neural correlates of peripersonal visuospatial neglect (PVN) in patients admitted to the Geneva Stroke Unit for an acute stroke or a transient ischemic attack (TIA). Methods: Eligible subjects were tested for PVN using both the Ota's discriminative cancellation task and a line bisection task....
Article
Spatial neglect is a neuropsychological syndrome in which patients fail to perceive and orient to stimuli located in the space contralateral to the lesioned hemisphere. It is characterized by a wide heterogeneity in clinical symptoms which can be grouped into distinct behavioral components correlating with different lesion sites. Moreover, damage t...
Article
Full-text available
The parahippocampal cortex (PHC) participates in both perception and memory. However, the way perceptual and memory processes cooperate when we navigate in our everyday life environment remains poorly understood. We studied a stroke patient presenting a brain lesion in the right PHC, which resulted in a mild and quantifiable topographic agnosia, an...
Data
Enhanced activity to familiar (recognized) compared with unfamiliar places in the control group (p < 0.001 for illustration).
Data
Supplementary Table 1. Standard neuropsychological assessment evaluating language, praxis, executive functions, memory, attention and visuo-perceptual abilities. Performances below cut-off in bold.Supplementary Table 2. Results from our in-house computerized battery comprising 12 subtests, 10 of which assessing different aspects of face perception....
Article
Full-text available
Recent research has led to the hypothesis that events which unfold in time might be spatially represented in a left-to-right fashion, resembling writing direction. Here we studied fourteen right-hemisphere damaged patients, with or without neglect, a disorder of spatial awareness affecting contralesional (here left) space processing and representat...
Article
Neurofeedback (NFB) involves a brain-computer interface that enables users to self-regulate neural activity in a closed-loop. Despite recent attempt to use NFB with EEG as a tool for rehabilitation of motor stroke, its potential for improving stroke-related impairments of attention -such as visuospatial neglect- remains underexplored. It is also un...
Article
Full-text available
Spatial perception abilities enable individuals to explore a visual field, to detect spatial position and to infer relationships between visual stimuli. Written words and text are conceptualized spatially along a horizontal mental line, but little is known about the way children develop these representations. The exact relationship between visuo-sp...
Article
Full-text available
Introduction Une lesion du tronc cerebral unilaterale (TC) provoque une inclinaison posturale et des desequilibres, souvent persistants a l’obscurite. Ces troubles semblent imputables a une perception erronee de l’orientation du corps par rapport a la verticale. Chez ces patients, la representation de l’orientation corporelle dans le plan horizonta...
Research
Full-text available
These results demonstrate how abnormal space perception might distort space representation and in turn affect reading and learning processes.
Article
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We tested whether human amygdala lesions impair vocal processing in intact cortical networks. In two functional MRI experiments, patients with unilateral amygdala resection either listened to voices and nonvocal sounds or heard binaural vocalizations with attention directed toward or away from emotional information on one side. In experiment 1, all...
Article
Every movement begins with action programming, and ends with a produced effect. Anosognosia for hemiplegia (AH), involving unawareness of motor deficits after brain damage, is a striking but also poorly understood symptom in clinical neurology. It has been suggested that it may result from a combination of cognitive and sensorimotor dysfunctions, i...
Article
Après une lésion cérébrale, la verticale subjective (VS) est souvent inclinée vers le côté controlésionnel. Ce biais est influencé par la présence d’une négligence spatiale et de trouble posturaux. Différents systèmes perceptifs peuvent être impliqués dans l’évaluation de la VS. Cette étude psychophysique et neuro-anatomique compare, chez des patie...
Article
Full-text available
La neuro-anatomie fonctionnelle de l’élaboration de la verticale subjective (VS) reste peu étudiée en neuroimagerie. Un unique travail en électroencéphalographie chez le sujet sain met en évidence le rôle des régions temporo-occipitale and pariéto-occipitale bilatérales. Notre objectif était de déterminer en IRM fonctionnelle les structures cérébra...
Article
Full-text available
Recent findings indicate that synchronous neural activity at rest influences human performance in subsequent tasks. Synchronization can occur in form of phase coupling or amplitude correlation. It is unknown whether these coupling types have differing behavioral significance at rest. To address this, we performed resting-state electroencephalograph...
Article
Full-text available
Patients with conversion disorder generally suffer from a severe neurological deficit which cannot be attributed to a structural neurological damage. In two patients with acute conversion paraplegia, investigation with functional magnetic resonance imaging (fMRI) showed that the insular cortex, a limbic-related cortex involved in body-representatio...
Article
Introduction. — The functional neuroanatomy of the egocentric and allocentric representations of space remains poorly studied with neuroimaging. Here we aim to determine brain structures subserving two different kinds of spatial representations centred on the main axis of either the body or the external scene. Method. — Sixteen healthy participants...
Article
Abstract Mograbi and Morris present a review of the literature on anosognosia of hemiplegia and dementia, including Alzheimer's disease. Their review focuses on aspects of implicit anosognosia. The authors' viewpoint is supported by the presentation of a general model on implicit anosognosia in Alzheimer's disease. The notions have important implic...