Explore the vast range of titles available.

Mapping the chimpanzee brain connectome and comparing it to that of humans is key to our understanding of similarities and differences in primate evolution that occurred after the split from their common ancestor around 6 million years ago. In contrast to studies on macaque species’ brains, fewer studies have specifically addressed the structural connectivity of the chimpanzee brain and its comparison with the human brain. Most comparative studies in the literature focus on the anatomy of the cortex and deep nuclei to evaluate how their morphology and asymmetry differ from that of the human brain, and some studies have emerged concerning the study of brain connectivity among humans, monkeys, and apes. In this work, we established a new white matter atlas of the deep and superficial white matter structural connectivity in chimpanzees. In vivo anatomical and diffusion-weighted magnetic resonance imaging (MRI) data were collected on a 3-Tesla MRI system from 39 chimpanzees. These datasets were subsequently processed using a novel fiber clustering pipeline adapted to the chimpanzee brain, enabling us to create two novel deep and superficial white matter connectivity atlases representative of the chimpanzee brain. These atlases provide the scientific community with an important and novel set of reference data for understanding the commonalities and differences in structural connectivity between the human and chimpanzee brains. We believe this study to be innovative both in its novel approach and in mapping the superficial white matter bundles in the chimpanzee brain, which will contribute to a better understanding of hominin brain evolution. •A novel superficial white matter bundles atlas of the chimpanzee brain.•An enhanced deep white matter bundles alas of the chimpanzee brain.•An open-source diffusion MRI processing for the atlasing of the chimpanzee brain connectivity.

Studies on the human brain have emphasized the loss of gray matter volume and decreased thickness during normal aging, along with variations in the density of small axon fibers across different regions of the corpus callosum (CC). Here, we investigated age-related changes in white matter connectivity in the CC and their association with handedness and cognitive decline in chimpanzees. To this end, microstructural measures of CC morphology were obtained from a sample of 49 chimpanzees. Initial assessments included quantifying streamline density, fractional anisotropy (FA), axial diffusivity (AD), and radial diffusivity (RD) values, which were then correlated with age and cognitive measures using the Primate Cognition Test Battery. We found an inverse association between streamline density and age in chimpanzees, particularly in the anterior and central CC regions. We also found an inverse association between FA and age in the splenium. Lastly, after controlling for age and sex, chimpanzees with higher cognition values also had higher FA values in anterior regions of the CC. Collectively, our results show that chimpanzees diverged from the typical human pattern, suggesting stronger interhemispheric connectivity integrity in frontal cortical brain regions compared to humans.

•Seasons significantly impact both the physiology and behavior of seasonal animals living in temperate and polar regions.•By developing novel tools and methodologies for brain registration and morphometric analysis, we examined brain plasticity in sheep, a large seasonal animal model, over the course of the seasons.•Voxel-based morphometry and grey matter thickness analysis show seasonal changes in grey matter organization in areas related to sensory processing, learning, memory, behavior control, and social cognition in sheep.•Our research underscores the importance of considering the time of year as a variable in MRI studies when studying general brain organization. At temperate and polar latitudes, animals and humans experience seasonal changes that impact physiology and behavior. In these habitats, the prevalence and severity of certain psychiatric disorders fluctuate seasonally. Such patterns imply that an adaptive system fine-tunes brain physiology in response to annual environmental changes, and alterations to this system may adversely affect mental health. To date, the core neuronal circuitry of the seasonal control of brain functioning is still largely unknown. To address this question, we identified brain regions sensitive to seasonal changes, using neuroimaging in the domestic sheep (Ovis aries), an animal model commonly used to study seasonality. Here, we developed MRI neuroinformatics resources (templates and atlas) dedicated to the analysis of the sheep brain and revealed that seasons broadly modify grey matter organization and volume of both cortical and subcortical regions involved in the control of homeostasis, sensory processing, learning, memory, behavior control, and social cognition. Many of these regions were not previously known to be affected by seasonal variations, highlighting that the seasonal control of brain function involves plasticity mechanisms across multiple brain sites.

Social interactions shape both the physiological and behavioural development of offspring, and poor care/early caregiver loss is known to promote adverse outcomes during infancy in both animals and humans. How affiliative behaviours impact the future development of offspring remains an open question. Here, we used Equus caballus (domestic horse) as a model to investigate this question. By coupling magnetic resonance imaging, longitudinal biobehavioural assessments and advanced multivariate statistical modelling, we found that prolonged maternal presence during infancy promotes the maturation of brain regions involved in both social behaviour (anterior cingulate cortex and retrosplenial cortex) and physiological regulation (hypothalamus and amygdala). Additionally, offspring benefiting from a prolonged maternal presence showed higher default mode network connectivity, improved social competences and feeding behaviours, and higher concentrations of circulating lipids (triglyceride and cholesterol). The findings of the present study underscore the salient role of social interactions in the development of allostatic regulation in offspring. The present study shows that maternal presence beyond early life remains crucial for brain, behavioural and physiological development in young horses, highlighting the importance of the mother–offspring relationship during a childhood-like stage.

The brainstem plays an essential role in many vital functions, such as autonomic control, consciousness and sleep, motricity, somatic afferent function, and cognition. Its involvement in several neurological diseases and the definition of brainstem targets for deep brain stimulation (DBS) explain the need for brainstem atlases describing its structural organization and connectivity from several modalities, from histology to ultrahigh field ex vivo MRI. Nonetheless, these atlases are often limited to a subpart of the brainstem or only include a single subject, the brainstem variability being considered low. This paper proposes a pipeline to create a high-resolution multisubject probabilistic atlas of the whole human brainstem based on four ultrahigh field ex vivo MRI datasets. The variability of the brainstem structures appears higher than usually considered, both for the volume and position of the central gray matter structures of the brainstem. This justifies the creation of atlases that capture the anatomical variability across subjects. The one we present here only included four specimens, but can easily be incremented due to its highly flexible design.

IntroductionElectroconvulsive therapy (ECT) induces an increase in hippocampal volume presumed to reflect neurogenesis in severely depressed patients. We hypothesized that Neurite Orientation Dispersion and Density Imaging (NODDI) provides in vivo evidence of hippocampal neurogenesis following ECT.MethodsThis prospective longitudinal study included 43 depressed patients treated by ECT. Three sequential evaluations (V1: baseline, V2: at 2 weeks into ECT, V3: 14 days within completing ECT) included a 3T MR-scan with 3D T1-weighted and multi-shell diffusion (b = 200/1500/2500 s/mm2, 30/45/60 directions) sequences and clinical assessment with depression scales. Q-ball, Diffusion Tensor and NODDI models provided the following metrics: axial (AD), radial (RD) and mean diffusivity (MD), fractional anisotropy (FA) and generalized FA (GFA), neurite density index (NDI), isotropic fraction (Fiso), neurite orientation and dispersion index (ODI). FreeSurfer was used to extract whole hippocampal and subfields volumes from T1-weighted images. A linear mixed-effect model assessed the changes over time in hippocampal volumes and mean diffusion metrics, and their relationship with clinical response was analyzed with ANOVA. Bonferroni corrections were applied.Results107 MRI were obtained at V1 (n = 43), V2 (n = 34) and V3 (n = 30) from 43 patients. Mean (± SD) interval between V1-V3 was 70 ± 25 days. Diffusion metrics in the hippocampus were: at V2, a decrease in left GFA, right AD, bilateral Fiso, and a bilateral ODI increase. Additionally, at V3, we observed a left MD decrease, bilateral AD decrease, right NDI increase, and bilateral ODI increase. Notably, NDI and Fiso changes were localized to the dentate gyrus but not to the hippocampal tail. ECT-responders showed a significant right hippocampus volume increase at 2 weeks into ECT.ConclusionAfter ECT, the observed increase in hippocampal volume is accompanied by bilateral changes in NODDI parameters, consistent with hippocampal neuroplasticity.

Diffusion MRI tractography (dMRI) has fundamentally transformed our ability to investigate white matter pathways in the human brain. While long-range connections have extensively been studied, superficial white matter bundles (SWMBs) have remained a relatively underexplored aspect of brain connectivity. This study undertakes a comprehensive examination of SWMB connectivity in both the human and chimpanzee brains, employing a novel combination of empirical and geometric methodologies to classify SWMB morphology in an objective manner. Leveraging two anatomical atlases, the Ginkgo Chauvel chimpanzee atlas and the Ginkgo Chauvel human atlas, comprising respectively 844 and 1375 superficial bundles, this research focuses on sparse representations of the morphology of SWMBs to explore the little-understood superficial connectivity of the chimpanzee brain and facilitate a deeper understanding of the variability in shape of these bundles. While similar, already well-known in human U-shape fibers were observed in both species, other shapes with more complex geometry such as 6 and J shapes were encountered. The localisation of the different bundle morphologies, putatively reflecting the brain gyrification process, was different between humans and chimpanzees using an isomap-based shape analysis approach. Ultimately, the analysis aims to uncover both commonalities and disparities in SWMBs between chimpanzees and humans, shedding light on the evolution and organization of these crucial neural structures.

The structural connectivity of animal brains can be revealed using post-mortem diffusion-weighted magnetic resonance imaging (MRI). Despite the existence of several structural atlases of avian brains, few of them address the bird’s structural connectivity. In this study, a novel atlas of the structural connectivity is proposed for the male Japanese quail (Coturnix japonica), aiming at investigating two lines divergent on their emotionality trait: the short tonic immobility (STI) and the long tonic immobility (LTI) lines. The STI line presents a low emotionality trait, while the LTI line expresses a high emotionality trait. 21 male Japanese quail brains from both lines were scanned post-mortem for this study, using a preclinical Bruker 11.7 T MRI scanner. Diffusion-weighted MRI was performed using a 3D segmented echo planar imaging (EPI) pulsed gradient spin-echo (PGSE) sequence with a 200 μm isotropic resolution, 75 diffusion-encoding directions and a b-value fixed at 4500 s/mm2. Anatomical MRI was likewise performed using a 2D anatomical T2-weighted spin-echo (SE) sequence with a 150 μm isotropic resolution. This very first anatomical connectivity atlas of the male Japanese quail reveals 34 labeled fiber tracts and the existence of structural differences between the connectivity patterns characterizing the two lines. Thus, the link between the male Japanese quail’s connectivity and its underlying anatomical structures has reached a better understanding.

Mapping the chimpanzee brain connectome, and comparing it to humans, is key to our understanding of similarities and differences in primate evolution that occurred after the split from their common ancestor around 6 million years ago. In contrast with macaque species brain studies, less studies have specifically addressed the structural connectivity of the chim-panzee brain and its comparison with the human brain. Most comparative studies in the liter-ature focus on the anatomy of the cortex and deep nuclei to evaluate how their morphometry and asymmetry differs from that of the human brain, and some studies have emerged concern-ing the study of brain connectivity between primates. In this work, we established a new white matter atlas of the deep and superficial white matter structural connectivity in chimpanzees. In vivo anatomical and diffusion weighted magnetic resonance imaging (MRI) data were collected on a 3 Tesla magnetic resonance imaging (MRI) system in 39 chimpanzees. These datasets were subsequently processed using a dedicated fiber clustering pipeline adapted to the chimpanzee brain enabling us to create two novel deep and superficial white matter connectivity atlases representative of the chimpanzee brain. These atlases provide the scientific community with an important and novel set of reference data for understanding the commonalities and differ-ences of the structural connectivity between the human and chimpanzee brains, which will contribute to a better understanding of the hominin brain evolution.