Brain Structure & Function最新文献

Recent rodent studies suggest that the claustrum complex, an evolutionarily conserved structure with widespread cortical connectivity, plays a role in modulation of anxiety-like behaviour via projections to the basolateral amygdala. However, this circuitry remains poorly defined in primates. Here, we investigated structural connectivity between the claustrum complex, amygdala, and prefrontal cortex in the adult common marmoset (Callithrix jacchus) using diffusion-weighted tractography and neuroanatomical tracing. Tracer injections were performed under anaesthesia via stereotaxic surgery. One marmoset received a biotinylated dextran amine injection into the basolateral amygdala, while four others received fluorescent retrograde tracers targeting the frontopolar cortex, orbitofrontal cortex, medial prefrontal cortex, and somatosensory cortex. Brains were processed for histology and tracer visualization. Diffusion weighted imaging and MRI tractography was performed on publicly available data from 24 marmosets from the Marmoset Brain Mapping Project (MBMv4; Tian et al. 2022; www.marmosetbrainmapping.org). The dorsal endopiriform nucleus was the region of the claustrum complex with the highest structural connectivity with both the amygdala and prefrontal cortex, showing particularly strong connectivity with the lateral amygdala and posterior orbitofrontal cortex, and more moderate connectivity with the medial prefrontal cortex. Our findings demonstrate a distinct claustro-amygdalo-prefrontal subcircuit in the marmoset, providing structural foundation for future studies examining the functional relevance of this circuitry in the primate brain.

Humans possess a distinctive capacity for technical reasoning-the ability to infer and manipulate the causal structure of the physical world. Although this faculty is central to technological innovation, its neural substrates remain incompletely understood. Here, we show that grey matter volume in the left area PF, within the supramarginal gyrus of the inferior parietal lobule, may predict individual differences in technical reasoning in healthy adults (N = 75; 54 females; mean age = 20.92 ± 3.28 years). This association remains independent of demographic factors, personality traits, and total brain volume. In contrast, grey matter volume in right prefrontal regions, examined solely as control areas, correlates with broader cognitive functions, such as fluid intelligence and abstract reasoning, but not with technical reasoning. These findings suggest that the left area PF may provide essential computational resources for technical cognition. Located in a parietal area that is disproportionately expanded in humans, the left area PF may serve as a technical hub, functioning as part of a broader fronto-temporo-parietal network that supports the human ability to generate, refine, and pass on complex technologies.

In Multiple Sclerosis, inflammation and neurodegeneration disrupt structural and functional brain networks. While the association between structural connectivity and disability is rather clear, functional connectivity changes are not yet characterised as a physiological response to the disease, as functionally meaningful adaptation or as a deceptive response. We explored the topology of brain networks of 65 Multiple Sclerosis patients over up to seven years in comparison to 59 controls. Connectomes based on probabilistic tractography from diffusion weighted imaging and resting-state MRI, were analysed with graph theory. The hub disruption index estimated connectivity perturbation in relation to the network hierarchy. In controls, we observed a transient increase in functional hub connectivity in the 5th and 6th age decade as a response to a subtle diffuse loss of structural connectivity, before structural and functional connectomes show a pronounced loss of hub connectivity. In Multiple Sclerosis, structural hub disruption was present from the disease onset while the transient upregulation of functional hub connectivity in the middle age was lacking. Patients seem to transition directly into an exhausted hub connectivity configuration. However, we observed the transient functional reorganisation of hubs in the first years after disease onset. Multiple Sclerosis patients present a probable physiological response to structural connectivity loss very early in the disease, potentially leading to an accelerated hub overload with accelerated neurodegeneration. The onset of chronic progression in the 5th age decade might be partially driven by the absence of the physiological increased hub connectivity observed in healthy individuals.

The Mongolian Gerbil (Meriones unguiculatus) diverged from rats/mice around 45 million years ago and developed adaptations to extreme temperatures and water scarcity. Another feature of the Mongolian Gerbils is their social monogamy similar to that of prairie voles. These observations suggest that there are potential differences in the Mongolian Gerbil brain that are distinct from that of rats and mice. The goal of the present study is to establish the extent to which the neuromeric organization of the brain is conserved in the Mongolian Gerbil and to gain insights on how evolutionary expansion and diversification of brain regions occur across species. Our data shows that the multineuromeric origin of tyrosine hydroxylase-positive processes in the Mongolian Gerbil is similar to that in mice and rats, spanning from the diencephalon, midbrain, and the rostral hindbrain. There are also observable anatomical differences. However, most of the components characteristic of these neuromeres are identifiable in the Mongolian gerbil, closely mirroring those found in mice and rats. Together, these findings suggest that the conserved neuromeric organization likely stems from a restricted genetic toolset that began in the Muridae family 45 million years ago, and that a profound reorganization of the fundamental structural plan delineating the neuromeric segmentation is not required for the emergence of diverse functionality among species of phylogenetically related families. Future studies are needed to establish how the genetic programs within each neuromeric unit are influenced by environmental factors that ultimately impact the size of the neuromeric derivatives and their functional connectivity.

Social phobia (SP) adversely affects individual as it often drives lower positive affect (PA) in social situations. This study aims to investigate the role of Lack of Control (LC) and its neural underpinnings in this process. We recruited 268 participants who completed measurements of SP tendency, LC, and PA at baseline (T1) and after two years (T2). All underwent a resting-state fMRI scan at T1. Findings revealed bidirectional associations among LC, SP tendency and PA, and the mediating effect of LC. Specifically, the LC at T1 was associated with SP tendency (β = 0.164) and PA (β = -0.191) at T2, while SP tendency (β = 0.103) and PA (β = -0.175) at T1 were associated with LC at T2. Additionally, Functional connectivity (FC) analyses and brain-behavior models further demonstrated that: (1) SP tendency at T1 was associated with LC at T2 through the FC networks involving the bilateral angular gyrus and left middle occipital gyrus (point estimate = -0.045, 95% CI [-0.070, -0.019]), and (2) LC at T2 was associated with PA at T2 via the FC networks of the left lingual gyrus, right cuneus and fusiform gyrus (point estimate = 0.040, 95% CI [0.007, 0.058]). This elucidates the cognitive and neural correlates through which SP tendency negatively affects PA, emphasizing the crucial role of LC in this relationship. Unraveling this mechanism offers a potential path for clinical interventions aimed at improving the mental health of individuals high in SP tendency.

The corpus callosum (CC) is the major tract connecting the two hemispheres in placental mammals and diffusion-weighted (DWI) MRI has revealed the meso/macroscopic organization of human CC and its organization of connectivity with the cortex. Here, we applied longitudinal DWI probabilistic tractography to study the CC fibers of mice across the adult lifespan. Our results reveal that connections of eight cortical areas can be delineated within the CC. The mouse CC organization aligns with the human topographical organization with frontal areas occupying the genus and parieto-occipital the posterior splenium region. A further regional analysis of passage fields showed stable field sizes in many of the studied areas over time. In contrast, several areas of the mouse default mode network and motor cortical regions show a decline in size with advancing age. Our analysis also identifies sex differences in the CC with female mice showing a larger orbitofrontal commissural connection. In summary, we confirm a mammalian-like organization of the CC in mice. Furthermore, we confirm an aging-related decline in the integrity of mouse white matter that aligns with previous findings in humans, thus opening up the possibility for future developmental in vivo studies across the entire lifespan using a mouse model.

The optic tectum of the embryonic chick brain consists of 15 principal laminae arranged in a precise order and each with a unique identity. The transmembrane proteins ephrin-B1 and ephrin-B2 are both expressed during tectal neurogenesis. To investigate their role in establishing tectal lamination, we transfected RCAS-based, replication-competent retroviral expression vectors in ovo to ectopically express ephrin-Bs in the developing tectum, and analyzed the subsequent effect of ectopic domains of ephrin-B2 on tectal lamination and on the trajectories and laminar patterning of RGC axons. We found that ectopic expression of ephrin-B2 in developing tectum disrupted the uniform laminar organization in the developing tectum: e.g. tectal layers are distended coincident with domains of ephrin-B2 overexpression creating a 'roller-coaster'-like effect. The laminar disturbance was not a result of increased or sustained cell proliferation or errors in tectal cell aggregation. Further, while tectal layer-specificity was maintained in transfection domains, afferent primary retinal ganglion cell axons circumvent ectopic domains of ephrin-B2 but appear unperturbed by ephrin-B1 domains, but were able to adjust to the undulations of tectal laminae, and terminate in the appropriate retinorecipient lamina. These findings demonstrate that ephrin-B2 is a repellent for RGC axons and has a unique role in the development of tectal lamination.