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Sven Joubert

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5 papers

1 author row

YNICL Journal 2020 Journal Article

Arterial stiffness cut-off value and white matter integrity in the elderly

Atef Badji
Adrián Noriega de la Colina
Agah Karakuzu
Tanguy Duval
Laurence Desjardins-Crépeau
Matthieu Parizet
Sven Joubert
Louis Bherer

OBJECTIVE: Central artery stiffness is a confirmed predictor of cardiovascular health status that has been consistently associated with cognitive dysfunction and dementia. The European Society of Hypertension has established a threshold of arterial stiffness above which a cardiovascular event is likely to occur. However, the threshold at which arterial stiffness alters brain integrity has never been established. METHODS: The aim of this study is to determine the arterial stiffness cut-off value at which there is an impact on the white matter microstructure. This study has been conducted with 53 cognitively elderly without dementia. The integrity of the white matter was assessed using diffusion tensor metrics. Central artery stiffness was evaluated by measuring the carotid-femoral pulse wave velocity (cfPWV). The statistical analyses included 4 regions previously denoted vulnerable to increased central arterial stiffness (the corpus callosum, the internal capsule, the corona radiata and the superior longitudinal fasciculus). RESULTS: The results of this study call into question the threshold value of 10 m/s cfPWV established by the European Society of Hypertension to classify patients in neuro-cardiovascular risk groups. Our results suggest that the cfPWV threshold value would be approximately 8.5 m/s when the microstructure of the white matter is taken as a basis for comparison. CONCLUSIONS: Adjustment of the cfPWV value may be necessary for a more accurate distinction between lower and higher risk group of patients for white matter microstructural injury related to arterial stiffness. Targeting the highest risk group for prevention methods may, in turn, help preserve brain health and cognitive functions.

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YNIMG Journal 2019 Journal Article

Arterial stiffness and white matter integrity in the elderly: A diffusion tensor and magnetization transfer imaging study

Atef Badji
Adrián Noriega de la Colina
Agah Karakuzu
Tanguy Duval
Laurence Desjardins-Crépeau
Sven Joubert
Louis Bherer
Maxime Lamarre-Cliche

Background and purpose The stiffness of large arteries and increased pulsatility can have an impact on the brain white matter (WM) microstructure, however those mechanisms are still poorly understood. The aim of this study was to investigate the association between central artery stiffness, axonal and myelin integrity in 54 cognitively unimpaired elderly subjects (65–75 years old). Methods The neuronal fiber integrity of brain WM was assessed using diffusion tensor metrics and magnetization transfer imaging as measures of axonal organization (Fractional anisotropy, Radial diffusivity) and state of myelination (Myelin volume fraction). Central artery stiffness was measured by carotid-femoral pulse wave velocity (cfPWV). Statistical analyses included 4 regions (the corpus callosum, the internal capsule, the corona radiata and the superior longitudinal fasciculus) which have been previously denoted as vulnerable to increased central artery stiffness. Results cfPWV was significantly associated with fractional anisotropy and radial diffusivity (p < 0. 05, corrected for multiple comparisons) but not with myelin volume fraction. Findings from this study also show that improved executive function performance correlates with Fractional anisotropy positively (p < 0. 05 corrected) as well as with myelin volume fraction and radial diffusivity negatively (p < 0. 05 corrected). Conclusions These findings suggest that arterial stiffness is associated with axon degeneration rather than demyelination. Controlling arterial stiffness may play a role in maintaining the health of WM axons in the aging brain.

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YNIMG Journal 2012 Journal Article

The impact of aging on gray matter structural covariance networks

Maxime Montembeault
Sven Joubert
Julien Doyon
Julie Carrier
Jean-François Gagnon
Oury Monchi
Ovidiu Lungu
Sylvie Belleville

Previous anatomical volumetric studies have shown that healthy aging is associated with gray matter tissue loss in specific cerebral regions. However, these studies may have potentially missed critical elements of age-related brain changes, which largely exist within interrelationships among brain regions. This magnetic resonance imaging research aims to assess the effects of aging on the organization of gray matter structural covariance networks. Here, we used voxel-based morphometry on high-definition brain scans to compare the patterns of gray matter structural covariance networks that sustain different sensorimotor and high-order cognitive functions among young (n =88, mean age=23. 5±3. 1years, female/male=55/33) and older (n =88, mean age=67. 3±5. 9years, female/male=55/33) participants. This approach relies on the assumption that functionally correlated brain regions show correlations in gray matter volume as a result of mutually trophic influences or common experience-related plasticity. We found reduced structural association in older adults compared with younger adults, specifically in high-order cognitive networks. Major differences were observed in the structural covariance networks that subserve the following: a) the language-related semantic network, b) the executive control network, and c) the default-mode network. Moreover, these cognitive functions are typically altered in the older population. Our results indicate that healthy aging alters the structural organization of cognitive networks, shifting from a more distributed (in young adulthood) to a more localized topological organization in older individuals.

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YNIMG Journal 2012 Journal Article

The role of the left anterior temporal lobe in exception word reading: Reconciling patient and neuroimaging findings

Maximiliano A. Wilson
Sven Joubert
Perrine Ferré
Sylvie Belleville
Ana Inés Ansaldo
Yves Joanette
Isabelle Rouleau
Simona Maria Brambati

Semantic dementia (SD) is a neurodegenerative disease that occurs following the atrophy of the anterior temporal lobes (ATLs). It is characterised by the degradation of semantic knowledge and difficulties in reading exception words (surface dyslexia). This disease has highlighted the role of the ATLs in the process of exception word reading. However, imaging studies in healthy subjects have failed to detect activation of the ATLs during exception word reading. The aim of the present study was to test whether the functional brain regions that mediate exception word reading in normal readers overlap those brain regions atrophied in SD. In Study One, we map the brain regions of grey matter atrophy in AF, a patient with mild SD and surface dyslexia profile. In Study Two, we map the activation pattern associated with exception word compared to pseudoword reading in young, healthy participants using fMRI. The results revealed areas of significant activation in healthy subjects engaged in the exception word reading task in the left anterior middle temporal gyrus, in a region observed to be atrophic in the patient AF. These results reconcile neuropsychological and functional imaging data, revealing the critical role of the left ATL in exception word reading.

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YNIMG Journal 2010 Journal Article

The role of the left anterior temporal lobe in the semantic processing of famous faces

Simona Maria Brambati
Sophie Benoit
Laura Monetta
Sylvie Belleville
Sven Joubert

Neuroimaging studies on healthy subjects have reported the involvement of the bilateral anterior temporal lobes (ATL) in recognizing known people. While the role of the right ATL in the semantic processing of known people is accepted, it is still matter of debate whether left ATL is implicated in the name retrieval or in the access to semantic information. In the present fMRI study, we modulated the level of specificity of the semantic categorization task of famous face stimuli in order to map the brain regions involved in the specific semantic processing controlling for automatic name access. Specifically, participants (n =12, mean age=23. 0±1. 7years, F/M=8/4) were asked to determine whether the stimulus photograph matched with the label of the profession category. Since the same set of stimuli was used for both specific and general conditions, contrasting these two conditions controlled for the activation due to the automatic access to the name of famous persons. Results showed that: 1) the right ATL was activated by a semantic categorization task of famous face stimuli at both general and specific level; 2) while controlling for the activation due to the automatic name retrieval, the left ATL showed increased activation during the specific categorization task; 3) the specificity of the semantic processing increased strength of connections towards the left ATL from the right lateral fusiform gyrus, devoted to the visual processing of faces, and from the right ATL. These findings support the idea of a crucial role of the left anterior temporal lobe in the processing of person-specific semantic information.

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