Brain Structure & Function最新文献

The structural brain connectome spans multiple length scales with varying complexity, from major commissural, association, and projection pathways down to much smaller pathways within brain regions. Diffusion MRI is often acquired for whole-brain coverage with limited spatial resolution for tractography purposes. How does this 'one size fits all' approach impact tractography and diffusion quantification, and do we need to care? Here, we discuss the concept of image resolution and define the structural image resolution limit, representing the resolution threshold at which a given dMRI setup can reliably resolve anatomical structures.

The insular cortex serves as a critical hub for human cognition, but how its anatomically distinct subregions coordinate diverse cognitive, emotional, and social functions remains unclear. Using the Human Connectome Project's multi-task fMRI dataset (N = 524), we investigated how insular subregions dynamically engage during seven different cognitive tasks spanning executive function, social cognition, emotion, language, and motor control. Our findings reveal five key principles of human insular organization. First, insular subregions maintain distinct functional signatures that enable reliable differentiation based on activation and connectivity patterns across cognitive domains. Second, these subregions dynamically reconfigure their network interactions in response to specific task demands while preserving their core functional architecture. Third, clear functional specialization exists along the insula's dorsal-ventral axis: the dorsal anterior insula selectively responds to cognitive control demands through interactions with frontoparietal networks, while the ventral anterior insula preferentially processes emotional and social information via connections with limbic and default mode networks. Fourth, we observed counterintuitive connectivity patterns during demanding cognitive tasks, with the dorsal anterior insula decreasing connectivity to frontoparietal networks while increasing connectivity to default mode networks-suggesting a complex information routing mechanism rather than simple co-activation of task-relevant networks. Fifth, while a basic tripartite model captures core functional distinctions, finer-grained parcellations revealed additional cognitive-affective domain-specific advantages that are obscured by simpler parcellation approaches. Our results illuminate how the insula's organization supports its diverse functional roles through selective engagement of distinct neural networks, providing a novel framework for understanding both normal cognitive function and clinical disorders involving insular dysfunction.

Artificial selection for behavioural traits can significantly affect the anatomy of brain regions related to the behaviour under selection. The homing pigeon (Columba livia) is a prime example of how anatomical changes can arise from artificial selection. Compared with feral and other pigeon breeds, homing pigeons have a much higher density and number neurons in the hippocampal formation, a region important for spatial memory and homing. Neuron numbers and density are, however, only one component of a brain region's processing capacity and whether hippocampal formation neuron size and morphology also differ remains unknown. Using Golgi staining and virtual microscopy, we reconstructed and quantified the size and morphology of neurons within the dorsomedial and dorsolateral regions of the hippocampal formation in homing and feral pigeons. While no significant differences were found in the size or morphology of dorsolateral neurons between the two breeds, homing pigeons had significantly smaller neurons (approximately 30% reduction in total volume and soma volume) in the dorsomedial region compared to feral pigeons. These findings suggest that smaller dorsomedial neurons in homing pigeons may facilitate increased neuronal packing density. How these differences in neuron size reflect behaviour in homing and feral pigeons has yet to be determined, but our results suggest that there may be behavioural and physiological differences in spatial cognition between the two breeds.

Delay discounting refers to the tendency to devalue rewards as the delay to their receipt increases. Reward sensitivity, defined as an individual's responsiveness to rewarding stimuli, has been suggested to influence delay discounting behavior. However, the neural mechanisms underlying this association remain largely unexplored. In the present study, we investigated the neural basis of the relationship between reward sensitivity and delay discounting using voxel-based morphometry (VBM) and resting-state functional connectivity (RSFC) analyses. Behaviorally, reward sensitivity was positively correlated with delay discounting, indicating that individuals with higher reward sensitivity tend to favor immediate rewards over delayed ones. Structurally, VBM analysis revealed that reward sensitivity was positively associated with gray matter volume in the dorsal anterior cingulate cortex (dACC). Moreover, RSFC results showed a negative correlation between reward sensitivity and functional connectivity between the dACC and the precuneus. Importantly, this functional connectivity partially mediated the relationship between reward sensitivity and delay discounting. These findings suggest that the functional connectivity between the dACC and the precuneus may serve as a neural pathway through which reward sensitivity influences delay discounting, offering new insights into the neural mechanisms underlying individual differences in intertemporal decision-making.

Savings refer to faster relearning upon re-exposure to a previously experienced movement perturbation. One theory posits that the brain recognizes past errors, enabling more efficient learning from them. If this is the case, there should be a modification in the neural response to errors during re-exposure to the perturbation. To investigate this hypothesis, we used fMRI to measure brain activity as participants adapted to a visuomotor perturbation across two sessions spaced one day apart, focusing on neural responses to movement errors. The magnitude of the movement error was incorporated into different types of GLMs to study error-related activation and co-activation (or functional connectivity). We identified a cerebello-thalamo-cortical network involved in processing movement errors during adaptation. We observed strengthened connectivity within this network during re-adaptation, particularly between the cerebellar lobule VI and the ventrolateral thalamus, as well as between the primary somatosensory cortex and the rostral cingulate motor zone. Importantly, participants with the greatest increases in connectivity strength also exhibited the largest amounts of savings. These results establish a link between the brain's ability to represent errors and the phenomenon of savings.

Threatening events elicit panic responses characterized by rapid movement, sympathetic arousal, and negative emotions-critical, instantaneous reactions that can determine survival in moments of acute danger. This study elucidates the neural circuit architecture underlying these responses, focusing on projections from the anterior cingulate cortex (ACC) to the dorsolateral periaqueductal gray (dlPAG) in male mice. We demonstrate that a subpopulation of GABAergic neurons (^ACC→dlPAG neurons) in the dlPAG receives direct glutamatergic inputs from the ACC and provides feed-forward inhibition to surrounding dlPAG neurons, serving as crucial intermediaries in regulating PAG output. Optogenetic suppression of ^ACC→dlPAG neurons elicited immediate and robust flight responses and pupil dilation. Moreover, the inhibition of ^ACC→dlPAG neurons produced aversive states, as evidenced by conditioned place aversion and modified Pavlovian fear conditioning paradigms. Our findings reveal that ^ACC→dlPAG neurons function as a gate for panic-like emotional and behavioral responses. This circuit architecture might allow for fine-tuned control of defensive behaviors, balancing the need for rapid action in genuine threat scenarios with the suppression of inappropriate responses in non-threatening situations.

Modeling the structural basis of neuronal connectivity has advanced our understanding of organization and function of the nervous system. Research has focused on predicting synaptic connectivity from the geometry of intersecting axonal and dendritic trees. We extended this framework to examine how the dendritic domains of neighbouring neurons intersect, aiming to understand how shared afferences and projection system topography arise. We studied intersections in pairs of ventral tegmental area (VTA) dopaminergic neurons (n = 15; 105 pairs), as if in their actual brain locations, using intersection of their 3D convex hulls polyhedra (CHPs) as proxies of domain intersection. Proximity increased intersection probability, but substantial data spreading suggested additional factors. We hypothesized that similarities in domain volume, orientation, somatic eccentricity, and shape increase intersection too. After independently normalizing each factor based on a common value or structural principle, we found that eccentricity homogenization most strongly increased intersection and model accuracy. Combining normalization of two or more factors further enhanced both metrics, though effects were factor dependent; simultaneous normalization of eccentricity and shape produced the greatest increases. We replicated the analysis with nigral dopaminergic neurons and found eccentricity to be the strongest determinant of intersection. This result held when systematically spacing CHPs and when using α-shapes for closer representation of dendritic architecture. Interestingly, VTA CHP pairs intersected more than nigral pairs at equal distances, suggesting greater geometrical heterogeneity in the latter. These findings suggest that differences in neuronal geometry contribute to segregated connectivity in topographically arranged neural circuits.

Swine have an excellent sense of smell and highly complex olfactory brain structures, which play a crucial role in their complex social interactions. In other mammals the olfactory system is known to exhibit significant plasticity, even during adulthood. The aim of this study was to investigate postnatal plasticity in olfactory areas of juvenile swine brains by studying immature cells immunoreactive for the microtubule-associated protein doublecortin (DCX). Using immunofluorescence, we studied DCX coexpression with the cell proliferation marker Ki-67, and different neuronal markers. Our results show the existence of numerous DCX + cells throughout the olfactory pallial areas. In some of them, we found DCX+/Ki-67 + coexpressing cells, suggesting that they were proliferating. Some of these proliferating cells were grouped in tangentially-oriented migratory-like chains, forming the rostral migratory stream to anterior olfactory area and olfactory bulb. Moreover, chains of DCX + cells were found in the external capsule and white matter adjacent to the temporal horn of the ventricle. Chains of DCX + cells were observed crossing the internal layers of the piriform and entorhinal cortices. In layer II of these cortices, DCX + cells of varying maturity degrees and neuronal phenotypes (including NeuN expression) were present. This suggests the existence of multiple migratory streams along the anteroposterior axis. Most DCX + immature cells in the migratory chains and in the anterior olfactory area, piriform and entorhinal cortices expressed the transcription factor Brn2 (Pou3f2), suggesting the incorporation of new glutamatergic neurons in these areas. Together, these results highlight the interest of swine to study the role of postnatal brain plasticity and their potential for regeneration in large, gyrencephalic brains.