Biology subjects

Vidal, J. P.

Publications and source records attributed to Vidal, J. P..

5 recordsLinked to original sources

bioRxiv2026

Thalamic nuclei insights into Alzheimer's disease

INTRODUCTIONThalamic nuclei support multiple cognitive processes, yet their integrity in biologically-defined Alzheimers disease (AD) remains unknown. METHODAmyloid status was determined using PET Centiloids >24 in 1,327 participants from ADNI. Combined with clinical diagnosis, this yielded six groups: amyloid-negative or positive CN-MCI-dementia/AD. Thalamic nuclei volumes were extracted from T1-weighted MRI using the HIPS-THOMAS algorithm. RESULTSLarge volume reductions in the anteroventral, mediodorsal, and pulvinar nuclei were observed in amyloid-positive MCI and AD. Reduced volumes were also evident in amyloid-positive CN, supporting preclinical AD. Adding the anteroventral nucleus improved cognitive status classification in Random Forest analyses. A phenotypic model integrating thalamic nuclei clearly distinguished amyloid-positive groups from amyloid-negative CN and reclassified non-AD patients with 68% of amyloid-negative MCI subjects as CN-like, and 27% of amyloid-positive CN as MCI-like. DISCUSSIONThalamic volumetry from conventional T1-weighted MRI enhances clinical insight into AD and provides a practical biomarker for disease intervention.

neuroscience↗

bioRxiv2025

A Reappraisal of the Role of the Mammillothalamic Tract in Memory Deficits Following Stroke in the Thalamus

The thalamus, traditionally viewed as a sensory relay station, is now recognized for its critical role in higher-order cognitive functions, including memory. While most research has focused on its distinct nuclei, the thalamus also contains crucial white matter tracts, such as the mammillothalamic tract (MTT), part of the Papez circuit. Despite its established role in memory, the MTT remains underappreciated in studies on the cognitive role of the thalamus, increasing the risk of misattributing memory functions to nearby thalamic nuclei. This study investigates the memory impact of thalamic strokes by considering disruption to the MTT. We examined 40 patients with chronic ischemic thalamic lesions and 45 healthy controls using neuropsychological assessments, focusing on the Free and Cued Selective Reminding Test (FCSRT) and high-resolution structural neuroimaging. Advanced imaging techniques, such as symptom mapping and disconnectome analyses, were employed to analyze the relationships between lesion sites, tract disconnections and cognitive outcomes. Additionally, the expression of calbindin-rich matrix cells and parvalbumin-rich core cells was examined to assess how the connectivity property of thalamic cells, and its disruption, can relate to cognitive deficits following a thalamic stroke. Patients with left-sided thalamic lesions, especially those involving the MTT, showed significant memory impairments. Symptom mapping identified a specific cluster of lesioned voxels in the left anterior-lateral thalamus, including the MTT, as being strongly associated with poorer memory performance. Disconnectome analysis confirmed that verbal memory deficits were associated with disruption of the MTT. Furthermore, a striking overlap was observed between the critical regions linked to memory deficits and calbindin-rich thalamic areas. However, this calbindin-rich region was also disrupted in patients without memory impairment, revealing that MTT disruption, and not lesions to this region, induced memory deficits in these patients. The identified FCSRT deficit cluster overlapped with brain regions consistently linked to memory processes following fMRI meta-analytic mapping of memory-related keywords. These findings challenge the traditional focus on thalamic nuclei and connector hubs, indicating a need to reappraise the importance of the MTT in memory impairment after a thalamic stroke. This study advocates for a shift in thalamic research, emphasizing the need to investigate tract-specific contributions and disruptions of the MTT but also of other tracts such as the interthalamic adhesion or amygdalo-fugal pathway, rather than holding only to a "nuclei-centric" view of the thalamus.

neuroscience↗

bioRxiv2024

A large cohort study (n = 591) on the impact of the presence or absence of the interthalamic adhesion: cognitive, neuroimaging, and genetic results

Both thalami can be connected by an Interthalamic Adhesion (IA). The extent of its presence varies among individuals and remains poorly understood. This study examines the IAs prevalence, anatomical variations, genetic determinants, and cognitive associations. Data from 591 healthy subjects (25-35 years) from the Human Connectome Project were analyzed and grouped as monozygotic (MZ) twins, dizygotic (DZ) twins, non-twin siblings, and unrelated individuals. MRI was used to characterize the IA, while neuropsychological assessments and Freesurfer parcellations were used to assess cognition and anatomical differences between subjects with or without an IA. The IA was absent in 12.7% of subjects, more commonly in males (20.0%) than females (6.3%), with no significant differences in age, education, or cognition between those with and without an IA. IA absence was associated with increased cerebrospinal fluid volumes, enlarged third ventricles, and thinning in several cortical areas. Genetic analysis revealed a higher concordance of IA presence among MZ twins (96%) than in other groups, indicating a strong genetic influence. The remaining 4% discrepancy was observed in male pairs only. This study underscores the genetic basis of IA, highlighting sexual dimorphism and neuroanatomical differences associated with its absence, though it does not affect cognition in healthy individuals.

neuroscience↗

bioRxiv2024

Factors behind poor cognitive outcome following a thalamic stroke

ObjectiveThalamic strokes produce a range of neurological, cognitive, and behavioral symptoms depending on the thalamic nuclei involved. While thalamic strokes are traditionally associated with severe cognitive deficits, recent studies suggest more modest impairments. This study aims to identify the factors that influence the severity of cognitive impairment following thalamic stroke. MethodsWe recruited 40 patients (median age 51) with chronic isolated thalamic stroke and 45 healthy subjects. All subjects underwent neuroimaging and neuropsychological testing. Cluster and principal component analyses were used to discriminate patients from healthy subjects based on cognitive performance. Disconnectome maps and cortical thickness were analyzed to understand the distant impact of thalamic strokes. ResultsTwo cognitive profiles emerged. Cluster 1 included mostly healthy subjects (n = 43) and patients with no or minor deficits (n = 20); Cluster 2 included patients (n = 19) and 2 healthy subjects with severe deficits of verbal memory, executive functions, and attention. Cluster 1 included all patients with right thalamic stroke. Cluster 2 included all patients with bilateral stroke or mammillothalamic tract disruption. Patients with left-sided stroke were equally divided between Cluster 1 and 2. Other significant differences included age, education, interthalamic adhesion disruption, lesion volume, and location. Disconnectome maps showed larger disruptions of the anterior thalamic projection in patients with left-sided stroke of Cluster 2. InterpretationContrary to common expectations, our findings indicate that many patients with thalamic stroke have relatively good cognitive outcomes. In contrast, we identified some of the factors behind poor outcomes that may help clinicians.

neuroscience↗

bioRxiv2024

Exploring the impact of interthalamic adhesion on human cognition: insights from healthy subjects and thalamic stroke patients

Background and ObjectivesInterthalamic adhesion (IA), also known as the massa intermedia, is a structure that connects the median borders of both thalami across the third ventricle. Given it is difficult to identify on routine neuroimaging, its anatomical variants and function remain poorly studied. The main objective of this study was to clarify the role of IA on cognition. Our main hypothesis was that thalamus stroke patients with an IA would show better performance on neuropsychological tests than individuals without an IA through possible compensatory mechanisms. MethodsThe study comprised a group of healthy subjects and a cohort of patients with isolated thalamic strokes at the chronic stage. All participants underwent 3T research T1w and FLAIR MRI as well as a neuropsychological assessment. The presence or absence of an IA and type of IA anatomical variant were evaluated by two independent reviewers. Results42 healthy subjects (mean age= 49) and 40 patients (mean age= 51) were finally included. 76% of participants had an IA, with a higher prevalence among women (92%) than men (61%). The presence or absence of an IA did not effect the neuropsychological performance of healthy subjects nor did the type of IA variant. Across all the tests, patients with an IA (n = 18) showed the lowest BF10 (157) while those without an IA (n = 10) exhibited the highest BF10 (10648) when compared to healthy subjects using a Bayesian rmANOVA. More specifically, patients without an IA performed more poorly in the verbal memory or Stroop task versus healthy subjects than patients with an IA. This effect was not explained by age, laterality of the infarct, volume or, localization of the lesion. Patients with an IA and lesions extending into the IA presented a similar trend to non-IA subjects which could however be explained by a greater volume of lesions. DiscussionIA does not appear to have a major role in cognition for healthy subjects but could play a compensatory part in patients with thalamic lesions.

neuroscience↗