bioRxiv Subject Collection: Neuroscience's Journal
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Monday, June 10th, 2024
| Time |
Event |
| 4:31p |
Sex and stress interactions in fear synchrony of mouse dyads
Socially coordinated threat responses support the survival of animal groups. Given their distinct social roles, males and females must differ in such coordination. Here, we report such differences during the synchronization of auditory-conditioned freezing in mouse dyads. To study the interaction of emotional states with social cues underlying synchronization, we modulated emotional states with prior stress or modified the social cues by pairing unfamiliar or opposite-sex mice. In same-sex dyads, males exhibited more robust synchrony than females. Stress disrupted male synchrony in a prefrontal cortex-dependent manner but enhanced it in females. Unfamiliarity moderately reduced synchrony in males but not in females. In dyads with opposite-sex partners, fear synchrony was resilient to both stress and unfamiliarity. Decomposing the synchronization process in the same-sex dyads revealed sex-specific behavioral strategies correlated with synchrony magnitude: following partners' state transitions in males and retroacting synchrony-breaking actions in females. Those were altered by stress and unfamiliarity. The opposite-sex dyads exhibited no synchrony-correlated strategy. These findings reveal sex-specific adaptations of socio-emotional integration defining coordinated behavior and suggest that sex-recognition circuits confer resilience to stress and unfamiliarity in opposite-sex dyads. | | 4:31p |
Mechanisms for dysregulation of excitatory-inhibitory balance underlying allodynia in dorsal horn neural subcircuits
Chronic pain is a wide-spread condition that is debilitating and expensive to manage, costing the United States alone around $600 billion in 2010. In a common type of chronic pain called allodynia, non-painful stimuli produce painful responses with highly variable presentations across individuals. While the specific mechanisms remain unclear, allodynia is hypothesized to be caused by the dysregulation of excitatory-inhibitory (E-I) balance in pain-processing neural circuitry in the dorsal horn of the spinal cord. In this work, we analyze biophysically-motivated subcircuit structures that represent common motifs in neural circuits in layers I-II of the dorsal horn. These circuits are hypothesized to be part of the neural pathways that mediate two different types of allodynia: static and dynamic. We use neural firing rate models to describe the activity of populations of excitatory and inhibitory interneurons within each subcircuit. By accounting for experimentally-observed responses under healthy conditions, we specify model parameters defining populations of subcircuits that yield typical behavior under normal conditions. Then, we implement a sensitivity analysis approach to identify the mechanisms most likely to cause allodynia-producing dysregulation of the subcircuits E-I signaling. We find that disruption of E-I balance generally occurs either due to downregulation of inhibitory signaling so that excitatory neurons are ''released'' from inhibitory control, or due to upregulation of excitatory neuron responses so that excitatory neurons ``escape'' their inhibitory control. Which of these mechanisms is most likely to occur, the subcircuit components involved in the mechanism, and the proportion of subcircuits exhibiting the mechanism can vary depending on the subcircuit structure. These results suggest specific hypotheses about diverse mechanisms that may be most likely responsible for allodynia, thus offering predictions for the high interindividual variability observed in allodynia and identifying targets for further experimental studies on the underlying mechanisms of this chronic pain condition. | | 4:31p |
Interaction of sortilin with apolipoprotein E3 enables neurons to use long-chain fatty acids as alternative metabolic fuel
Sortilin (SORT1) is a lipoprotein receptor that shows genome-wide association with hypercholesterolemia, explained by its ability to control hepatic output of lipoproteins. Remarkably, SORT1 also shows genome-wide association with Alzheimer disease (AD) and frontotemporal lobe dementia, the most prevalent forms of age-related dementias. Yet, its contribution to human brain lipid metabolism and health remains unclear. Using humanized mouse strains and iPSC-based cell models of brain lipid homeostasis, we document that sortilin mediates neuronal uptake of polyunsaturated fatty acids carried by apoE. Internalized lipids are converted into ligands for PPARalpha, inducing transcription profiles that enable neurons to use long-chain fatty acids as metabolic fuel. This pathway works with apoE3, but is lost with the AD risk factor apoE4, which disrupts the endocytic activity of sortilin. We document a role for the lipoprotein receptor sortilin in metabolic fuel choice in neurons, possibly crucial when supply with glucose is limited, as in the aging brain. | | 7:17p |
SpaDE: Semantic Locality Preserving Biclusteringfor Neuroimaging Data
The most discriminative and revealing patterns in the neuroimaging population are often confined to smaller subdivisions of the samples and features. Especially in neuropsychiatric conditions, symptoms are expressed within micro subgroups of individuals and may only underly a subset of neurological mechanisms. As such, running a whole-population analysis yields suboptimal outcomes leading to reduced specificity and interpretability. Biclustering is a potential solution since subject heterogeneity makes one-dimensional clustering less effective in this realm. Yet, high dimensional sparse input space and semantically incoherent grouping of attributes make post hoc analysis challenging. Therefore, we propose a deep neural network called semantic locality preserving auto decoder (SpaDE), for unsupervised feature learning and biclustering. SpaDE produces coherent subgroups of subjects and neural features preserving semantic locality and enhancing neurobiological interpretability. Also, it regularizes for sparsity to improve representation learning. We employ SpaDE on human brain connectome collected from schizophrenia (SZ) and healthy control (HC) subjects. The model outperforms several state-of-the-art biclustering methods. Our method extracts modular neural communities showing significant (HC/SZ) group differences in distinct brain networks including visual, sensorimotor, and subcortical. Moreover, these bi-clustered connectivity substructures exhibit substantial relations with various cognitive measures such as attention, working memory, and visual learning. | | 7:17p |
Loss of neuronal lysosomal acid lipase drives amyloid pathology in Alzheimer's disease
Underlying drivers of late-onset Alzheimer's disease (LOAD) pathology remain unknown. However, multiple biologically diverse risk factors share a common pathological progression. To identify convergent molecular abnormalities that drive LOAD pathogenesis we compared two common midlife risk factors for LOAD, heavy alcohol use and obesity. This revealed that disrupted lipophagy is an underlying cause of LOAD pathogenesis. Both exposures reduced lysosomal flux, with a loss of neuronal lysosomal acid lipase (LAL). This resulted in neuronal lysosomal lipid (NLL) accumulation, which opposed A{beta} localization to lysosomes. Neuronal LAL loss both preceded (with aging) and promoted (targeted knockdown) A{beta} pathology and cognitive deficits in AD mice. The addition of recombinant LAL ex vivo and neuronal LAL overexpression in vivo prevented amyloid increases and improved cognition. In WT mice, neuronal LAL declined with aging and correlated negatively with entorhinal A{beta}. In healthy human brain, LAL also declined with age, suggesting this contributes to the age-related vulnerability for AD. In human LOAD LAL was further reduced, correlated negatively with A{beta}1-42, and occurred with polymerase pausing at the LAL gene. Together, this finds that the loss of neuronal LAL promotes NLL accumulation to impede degradation of A{beta} in neuronal lysosomes to drive AD amyloid pathology. | | 7:17p |
Endothelin B receptor inhibition rescues aging-dependent neuronal regenerative decline
Peripheral sensory neurons regenerate their axons after injury to regain function, but this ability declines with age. The mechanisms behind this decline are not fully understood. While excessive production of endothelin 1 (ET-1), a potent vasoconstrictor, is linked to many diseases that increase with age, the role of ET-1 and its receptors in axon regeneration is unknown. Using a single cell RNAseq approach, we reveal that in dorsal root ganglia (DRG), satellite glial cells (SGCs), which completely envelop the sensory neuron soma, express the endothelin B receptor (ETBR), while ET-1 is expressed by endothelial cells. Inhibition of ETBR ex-vivo in DRG explant cultures improves axon growth in both adult and aged conditions. In vivo, treatment with the FDA-approved compound, Bosentan, improves axon regeneration and reverses the age-dependent decrease in axonal regenerative capacity. Bosentan treatment also enhances the expression of connexin 43 in SGCs after injury in adult and aged mice. These results reveal that inhibiting ETBR function enhances axon regeneration and rescues the age-dependent decrease in axonal regenerative capacity, providing a potential avenue for future therapies. | | 8:34p |
Axon length-dependent synapse loss is mediated by neuronal cytokine-induced glial phagocytosis
Many neurodegenerative disorders (NDDs) preferentially affect neurons with long or complex axonal arbors, but our understanding of this specific vulnerability is limited. Using Drosophila larval class IV dendrite arborization (C4da) neurons, we found that neuronal activation of the integrated stress response (ISR) induces axon length-dependent degeneration (LDD). We identified the Interleukin-6 homologue unpaired 3 (upd3) as both necessary and sufficient for LDD in C4da neurons. Upd3 recruits glial cells to phagocytose presynapses preferentially on neurons with long axons, revealing an intrinsic axon length-dependent vulnerability to glia-mediated presynapse removal. Finally, we found that axon length-dependent presynapse loss in fly models of human NDDs utilized this pathway. Altogether, our studies identify inflammatory cytokine signaling from neurons to glia as a key determinant in axon length-dependent vulnerability. | | 8:34p |
Broken time reversal symmetry in visual motion detection
Our intuition suggests that when a movie is played in reverse, our perception of motion in the reversed movie will be perfectly inverted compared to the original. This intuition is also reflected in many classical theoretical and practical models of motion detection. However, here we demonstrate that this symmetry of motion perception upon time reversal is often broken in real visual systems. In this work, we designed a set of visual stimuli to investigate how stimulus symmetries affect time reversal symmetry breaking in the fruit fly Drosophila's well-studied optomotor rotation behavior. We discovered a suite of new stimuli with a wide variety of different properties that can lead to broken time reversal symmetries in fly behavioral responses. We then trained neural network models to predict the velocity of scenes with both natural and artificial contrast distributions. Training with naturalistic contrast distributions yielded models that break time reversal symmetry, even when the training data was time reversal symmetric. We show analytically and numerically that the breaking of time reversal symmetry in the model responses can arise from contrast asymmetry in the training data, but can also arise from other features of the contrast distribution. Furthermore, shallower neural network models can exhibit stronger symmetry breaking than deeper ones, suggesting that less flexible neural networks promote some forms of time reversal symmetry breaking. Overall, these results reveal a surprising feature of biological motion detectors and suggest that it could arise from constrained optimization in natural environments. |
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