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340 results on '"Saj, Arnaud"'

6. An immersive virtual reality tool for assessing left and right unilateral spatial neglect.

Author

Thomasson, Marine, Perez‐Marcos, Daniel, Crottaz‐Herbette, Sonia, Brenet, Fanny, Saj, Arnaud, Bernati, Thérèse, Serino, Andrea, Tadi, Tej, Blanke, Olaf, and Ronchi, Roberta

Subjects
CEREBRAL dominance, BRAIN damage, INSULAR cortex, VIRTUAL reality, TEMPORAL lobe, UNILATERAL neglect, PERSONAL space
Abstract

The reported rate of the occurrence of unilateral spatial neglect (USN) is highly variable likely due to the lack of validity and low sensitivity of classical tools used to assess it. Virtual reality (VR) assessments try to overcome these limitations by proposing immersive and complex environments. Nevertheless, existing VR‐based tasks are mostly focused only on near space and lack analysis of psychometric properties and/or clinical validation. The present study evaluates the clinical validity and sensitivity of a new immersive VR‐based task to assess USN in the extra‐personal space and examines the neuronal correlates of deficits of far space exploration. The task was administrated to two groups of patients with right (N = 28) or left (N = 11) hemispheric brain lesions, also undergoing classical paper‐and‐pencil assessment, as well as a group of healthy participants. Our VR‐based task detected 44% of neglect cases compared to 31% by paper‐and‐pencil tests in the total sample. Importantly, 30% of the patients (with right or left brain lesions) with no clear sign of USN on the paper‐and‐pencil tests performed outside the normal range in the VR‐based task. Voxel lesion‐symptom mapping revealed that deficits detected in VR were associated with lesions in insular and temporal cortex, part of the neural network involved in spatial processing. These results show that our immersive VR‐based task is efficient and sensitive in detecting mild to strong manifestations of USN affecting the extra‐personal space, which may be undetected using standard tools. [ABSTRACT FROM AUTHOR]

Published
2024
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31. Deficits in cognitive and affective theory of mind relate to dissociated lesion patterns in prefrontal and insular cortex

Author

Corradi-Dell'Acqua, Corrado, Ronchi, Roberta, Thomasson, Marine, Saj, Arnaud, and Vuilleumier, Patrik

Abstract

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 understand others’ emotions and ToM. This discrepancy might underlie the fact that neuropsychological investigations often correlate behavioural impairments only to the lesion site, without considering the impact that the insult might have on other interconnected brain structures. Here we took a network-based approach, and investigated whether deficits in understanding people’s emotional and cognitive states relate to damage to similar or differential structures. By combining information from 40 unilateral stroke damaged patients, with normative connectome data from 92 neurotypical individuals, we estimated lesion-induced dysfunctions across the whole brain, and modeled them in relation to patients’ behavior. We found a striking dissociation between networks centered in the insular and prefrontal cortex, whose dysfunctions led to selective impairments in understanding emotions and beliefs respectively. Instead, no evidence was observed for neural structures shared between the two conditions. Overall, our data provide novel evidence of segregation between brain networks subserving social inferential abilities Corradi-Dell’Acqua C., Ronchi R., Thomasson M., Bernati T., Saj A. & Vuilleumier P. "Deficits in cognitive and affective theory of mind relate to dissociated lesion patterns in prefrontal and insular cortex" Cortex

Published
2022
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47. Two Intrinsic Coupling Types for Resting-State Integration in the Human Brain

Author

Guggisberg, Adrian, Rizk, Sviatlana, Ptak, Radek, Di Pietro, Marie, Saj, Arnaud, Lazeyras, François, Lovblad, Karl-Olof, Schnider, Armin, Pignat, Jean-Michel, Guggisberg, Adrian, Rizk, Sviatlana, Ptak, Radek, Di Pietro, Marie, Saj, Arnaud, Lazeyras, François, Lovblad, Karl-Olof, Schnider, Armin, and Pignat, Jean-Michel

Abstract

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 electroencephalography (EEG) and source connectivity analysis in several populations of healthy subjects and patients with brain lesions. We systematically compared different types and frequencies of neural synchronization and investigated their association with behavioral performance in verbal and spatial attention tasks. Behavioral performance could be consistently predicted by two distinct resting-state coupling patterns: (1) amplitude envelope correlation of beta activity between homologous areas of both hemispheres, (2) lagged phase synchronization in EEG alpha activity between a brain area and the entire cortex. A disruption of these coupling patterns was also associated with neurological deficits in patients with stroke lesions. This suggests the existence of two distinct network systems responsible for resting-state integration. Lagged phase synchronization in the alpha band is associated with global interaction across networks while amplitude envelope correlation seems to be behaviorally relevant for interactions within networks and between hemispheres. These two coupling types may therefore provide complementary insights on brain physiology and pathology.

Published
2021

49. A novel computerized assessment of manual spatial exploration in unilateral spatial neglect.

Author

Pierce, Jordan E., Ronchi, Roberta, Thomasson, Marine, Rossi, Irene, Casati, Carlotta, Saj, Arnaud, Vallar, Giuseppe, and Vuilleumier, Patrik

Abstract

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 other modalities as well. Here we developed a novel manual exploration test using a touch screen computer to quantify spatial search behaviour without visual input. Twelve chronic stroke patients with left neglect and 27 patients without neglect (based on clinical tests) completed our task. Four of the 12 "neglect" patients exhibited clear signs of neglect on our task as compared to "non-neglect" patients and healthy controls, and six other patients (from both groups) also demonstrated signs of neglect compared to healthy controls only. While some patients made asymmetrical responses on only one task, generally, patients with the strongest neglect performed poorly on multiple tasks. This suggests that representations associated with different modalities may be affected separately, but that severe forms of neglect are more likely related to damage in a common underlying representation. Our manual exploration task is easy to administer and can be added to standard neglect screenings to better measure symptom severity. [ABSTRACT FROM AUTHOR]

Published
2022
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