bioRxiv Subject Collection: Neuroscience's Journal
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Wednesday, April 3rd, 2024
| Time |
Event |
| 12:46a |
Sex-specific brain effective connectivity patterns associated with negative emotions
Sex differences in effective brain connectivity in emotional intelligence, emotional regulation, and stimuli-induced negative emotions have been highlighted in previous research. However, to our knowledge, no research has yet investigated the sex-specific effective connectivity related to negative emotions in healthy population during resting-state. The goal of this study is to find the association between sex-specific resting-state effective brain connectivity and basic negative emotions. For this, we have employed the NIH emotion battery of the three self-reported, basic negative emotions: anger-affect, fear-affect, and sadness which we divided into high, moderate, and low emotion scores in each. The dataset comprises 1079 subjects (584 females) from HCP Young Adults. We selected large-scale resting-state brain networks important for emotional processing namely default mode, executive, and salience networks. We employed subject-level analysis using spectral dynamic causal modelling and group-level association analyses using parametric empirical Bayes. We report association of the self-connection of left hippocampus in females in high anger-affect, fear-affect, and sadness, whereas in males we found involvement of dorsal anterior cingulate cortex (dACC) in all three negative emotions - association of right amygdala to dACC in high anger-affect, association of the self-connection of dACC in high fear-affect, and association of dACC to left hippocampus in high sadness. Our findings primarily revealed the effective brain connectivity that is related to the higher levels of negative emotions that may lead to psychiatric disorders if not regulated. Sex-specific therapies and interventions that target psychopathology can be more beneficial when informed by the sex-specific resting-state effective connectivity. | | 2:46a |
APOE regulates the transport of GM1
Apolipoprotein E (APOE) is responsible for lipid transport, including cholesterol transport and clearance. While the epsilon 4 allele of APOE (APOE4) is associated with a significant genetic risk factor for late-onset Alzheimer's disease (AD), no mechanistic understanding of its contribution to AD etiology has been established yet. In addition to cholesterol, monosialotetrahexosylganglioside (GM1) is a crucial lipid component in cell membranes and has been implicated in promoting the aggregation of amyloid beta protein, a key protein associated with AD. Here, we ask whether there are direct interactions between APOE and GM1 that further impact AD pathology. We find that both APOE3 and APOE4 exhibit superior binding affinity to GM1 compared to cholesterol and have an enhanced cellular uptake to GM1 lipid structures than cholesterol lipid structures. APOE regulates the transport process of GM1 depending on the cell type, which is influenced by the expression of APOE receptors in different cell lines and alters GM1 contents in cell membranes. We also find that the presence of GM1 alters the secondary structure of APOE3 and APOE4 and enhances the binding affinity between APOE and its receptor low-density lipoprotein receptor (LDLR), consequently promoting the cellular uptake of lipid structures in the presence of APOE. To understand the enhanced cellular uptake observed in lipid structures containing 20% GM1, we determined the distribution of GM1 on the membrane and found that GM1 clustering in lipid rafts, thereby supporting the physiological interaction between APOE and GM1. Overall, we find that APOE plays a regulatory role in GM1 transport, and the presence of GM1 on the lipid structures influences this transport process. Our studies introduce a plausible direct link between APOE and AD etiology, wherein APOE regulates GM1, which, in turn, promotes amyloid beta protein oligomerization and aggregation. | | 2:46a |
Rat Anterior Insula Symmetrically Represents Tickling-Induced Playful Emotions
Social play, an integral aspect of animal behavior, is inherently associated with positive emotions, yet the neuronal underpinnings of these playful states remain inadequately explored. We examined the anterior insula's involvement in processing tickle-induced playful emotions in rats. Our findings revealed diverse patterns of insular activity during tickling, with 20% of the recorded units displaying strong activation, and another 20% exhibiting inhibition. These units responded similarly to other playful contexts, such as gentle touch and hand chase, but not to neutral locomotion. Tickle-activated units demonstrated a positive correlation of firing rates with appetitive vocalization rates, whereas tickle-inhibited units showed a negative correlation. Distinct spike waveforms were associated with the tickle response patterns, suggesting potential cell-type dependencies. However, pharmacological manipulation of the global anterior insula did not yield observable effects on play behavior in rats. Anterograde tracing revealed extensive insular projections to areas including the amygdala and nucleus accumbens. Taken together, our findings suggest that the anterior insula symmetrically represents tickle-induced playful emotional states. | | 2:46a |
Orbitofrontal high-gamma reflects spike-dissociable value and decision mechanisms
The orbitofrontal cortex (OFC) plays a crucial role in value-based decision-making. While previous research has focused on spiking activity in OFC neurons, the role of OFC local field potentials (LFPs) in decision-making remains unclear. LFPs are important because they can reflect synaptic and subthreshold activity not directly coupled to spiking, and because they are potential targets for less invasive forms of brain-machine interface (BMI). We recorded LFPs and spiking activity using multi-channel vertical probes while monkeys performed a two-option value-based decision-making task. We compared the value- and decision-coding properties of high-gamma range LFPs (HG, 50-150 Hz) to the coding properties of spiking multi-unit activity (MUA) recorded concurrently on the same electrodes. Results show that HG and MUA both represent the values of decision targets, and that their representations have similar temporal profiles in a trial. However, we also identified value-coding properties of HG that were dissociable from the concurrently-measured MUA. On average across channels, HG amplitude increased monotonically with value, whereas the average value encoding in MUA was net neutral. HG also encoded a signal consistent with a comparison between the values of the two targets, a signal which was much weaker in MUA. In individual channels, HG was better able to predict choice outcomes than MUA; however, when simultaneously recorded channels were combined in population-based decoder, MUA provided more accurate predictions than HG. Interestingly, HG value representations were accentuated in channels in or near shallow cortical layers, suggesting a dissociation between neuronal sources of HG and MUA. In summary, we find that HG signals are dissociable from MUA with respect to cognitive variables encoded in prefrontal cortex, evident in the monotonic encoding of value, stronger encoding of value comparisons, and more accurate predictions about behavior. High-frequency LFPs may therefore be a viable - or even preferable - target for BMIs to assist cognitive function, opening the possibility for less invasive access to mental contents that would otherwise be observable only with spike-based measures. | | 2:46a |
Biomaterial Scaffold Stiffness Influences the Foreign Body Reaction, Tissue Stiffness, Angiogenesis and Neuroregeneration in Spinal Cord Injury
Biomaterial scaffold engineering presents great potential in promoting axonal regrowth after spinal cord injury (SCI), yet persistent challenges remain, including the surrounding host foreign body reaction and improper host-implant integration. Recent advances in mechanobiology spark interest in optimizing the mechanical properties of biomaterial scaffolds to alleviate the foreign body reaction and facilitate seamless integration. The impact of scaffold stiffness on injured spinal cords has not been thoroughly investigated. Herein, we introduce stiffness-varied alginate anisotropic capillary hydrogel scaffolds implanted into adult rat C5 spinal cords post-lateral hemisection. Four weeks post-implantation, scaffolds with a stiffness approaching that of the spinal cord effectively minimize the host foreign body reaction via yes-associated protein (YAP) nuclear translocation. Concurrently, the softest scaffolds maximize cell infiltration and angiogenesis, fostering significant axonal regrowth but limiting the rostral-caudal linear growth. Furthermore, as measured by atomic force microscopy (AFM), the surrounding spinal cord softens when in contact with the stiffest scaffold while maintaining a natural level in contact with the softest one. In conclusion, our findings underscore the pivotal role of stiffness in scaffold engineering for SCI in vivo, paving the way for the optimal development of efficacious biomaterial scaffolds for tissue engineering in the central nervous system. | | 3:17a |
Text-related functionality of visual human pre-frontal activations revealed through neural network convergence
The functional role of visual activations of human pre-frontal cortex remains a deeply debated question. Its significance extends to fundamental issues of functional localization and global theories of consciousness. Here we addressed this question by comparing potential parallels between the relational structure of prefrontal visual activations and visual and textual-trained deep neural networks (DNNs). The frontal visual relational structures were revealed in intra-cranial recordings of human patients, conducted for clinical purposes, while the patients viewed familiar images of faces and places. Our results reveal that visual relational structures in frontal cortex were, surprisingly, predicted by text and not visual DNNs. Importantly, the temporal dynamics of these correlations showed striking differences, with a rapid decline over time for the visual component, but persistent dynamics including a significant image offset response for the text component. The results point to a dynamic text-related function of visual prefrontal responses in the human brain. | | 3:17a |
Mid-infrared photoacoustic brain imaging enabled by cascaded gas-filled hollow-core fiber lasers
SignificanceExtending the photoacoustic microscopy (PAM) into the mid-infrared (MIR) molecular fingerprint region constitutes a promising route towards label-free imaging of biological molecular structures. Realizing this objective requires a high-energy nano-second MIR laser source. However, existing MIR laser technologies are limited to either low pulse energy or free-space structure which is sensitive to environmental conditions. Fiber lasers are promising technologies for PAM for their potential of offering both high pulse energy and robust performance against environmental conditions. However, MIR high energy fiber laser has not yet been used for PAM because it is still at the infant research stage.
AimWe aim to employ the emerging gas-filled anti-resonant hollow-core fiber (ARHCF) laser technology for MIR-PAM for the purpose of imaging myelin-rich regions in a mouse brain.
ApproachThis laser source is developed with a [~]2.75 J high-pulse-energy nano-second laser at 3.4 m, targeting the main absorption band of myelin sheaths, the primary chemical component of axons in the central nervous system. The laser mechanism relies on two-orders gas-induced vibrational stimulated Raman scattering (SRS) for nonlinear wavelength conversion, starting from a 1060 nm pump laser to 1409 nm through the 1st order Stokes generation in the nitrogen-filled 1st stage ARHCF, then, from 1409 nm to 3.4 m through the 2nd stage hydrogen-filled ARHCF.
ResultsThe developed Raman laser was used for the first time for transmission-mode MIR-PAM of mouse brain regions containing rich myelin structures.
ConclusionsThis work pioneers the potential use of high-energy and nano-second gas-filled ARHCF laser source to MIR-PAM, with a first attempt to report this kind of fiber laser source for PAM of lipid-rich myelin regions in a mouse brain. The proposed ARHCF laser technology is also expected to generate high-energy pulses at the ultraviolet (UV) region, which can significantly improve the lateral resolution of the PAM. | | 3:17a |
Experience-induced drift in the neural coding of individual differences in perception
Like humans, no two rodents like precisely the same tastes. Here, we ask whether these individual differences determine cortical taste responses, late epochs of which "code" palatability. We show that rats individual preferences match late-epoch responses with a fidelity significantly higher than that expected on the basis of canonical palatability rankings. A single tasting session, however, induces "neural drift," such that previously-assessed preferences are no longer reflected in cortical activity. | | 3:17a |
Elevating levels of the endocannabinoid 2-arachidonoylglycerol blunts opioid reward but not analgesia
Converging findings have established that the endocannabinoid (eCB) system serves as a possible target for the development of new treatments for pain as a complement to opioid-based treatments. Here we show in male and female mice that enhancing levels of the eCB, 2-arachidonoylglycerol (2-AG), through pharmacological inhibition of its catabolic enzyme, monoacylglycerol lipase (MAGL), either systemically or in the ventral tegmental area (VTA) with JZL184, leads to a substantial attenuation of the rewarding effects of opioids in male and female mice using conditioned place preference and self-administration paradigms, without altering their analgesic properties. These effects are driven by CB1 receptors (CB1Rs) within the VTA as VTA CB1R conditional knockout, counteracts the effects of JZL184 Conversely, pharmacologically enhancing the levels of the other eCB, anandamide (AEA), by inhibition of fatty acid amide hydrolase (FAAH) has no effect on opioid reward or analgesia. Using fiber photometry with fluorescent sensors for calcium and dopamine (DA), we find that enhancing 2-AG levels diminishes opioid reward-related nucleus accumbens (NAc) activity and DA neurotransmission. Together these findings reveal that 2-AG counteracts the rewarding properties of opioids and provides a potential adjunctive therapeutic strategy for opioid-related analgesic treatments. | | 3:17a |
Functional activation of dorsal striatum astrocytes improves movement deficits in hemi-parkinsonian mice
Parkinson's disease (PD) is characterized by the degeneration of dopaminergic nigrostriatal inputs, which causes striatal network dysfunction and leads to pronounced motor deficits. Recent evidence highlights astrocytes as a potential local source of striatal network modulation. However, it remains unknown how dopamine loss affects striatal astrocyte activity and whether astrocyte activity regulates behavioral deficits in PD. We addressed these questions by performing astrocyte-specific calcium recordings and manipulations using in vivo fiber photometry and chemogenetics. We find that locomotion elicits astrocyte calcium activity over a slower timescale than neurons. Unilateral dopamine depletion reduced locomotion-related astrocyte responses. Chemogenetic activation facilitated astrocyte activity, and improved asymmetrical motor deficits and open field exploratory behavior in dopamine lesioned mice. Together, our results establish a novel role for functional striatal astrocyte signaling in modulating motor function in PD and highlight non-neuronal targets for potential PD therapeutics. | | 10:48a |
Functional recruitment and connectivity of the cerebellum supports the emergence of Theory of Mind in early childhood
There is accumulating evidence that the human cerebellum is heavily implicated in adult social cognition. Yet, its involvement in the development of Theory of Mind (ToM), a hallmark of social cognition, remains elusive. In a functional MRI study involving children with emerging ToM abilities (N=41, age range: 3-12 years) and adults (N=78), we showed that children with ToM abilities activated cerebellar Crus I-II in response to ToM events during a movie-watching task, similar to adults. This activation was absent in children lacking ToM abilities. Functional connectivity profiles between cerebellar and cerebral ToM regions differed as a function of childrens ToM abilities. Notably, task-driven connectivity shifted from upstream to downstream connections between cerebellar and cerebral ToM regions from childhood to adulthood. Greater dependence on connections emerging from the cerebellum early in life suggests an important role of the cerebellum in establishing the cognitive processes underlying ToM in childhood and thus for the undisrupted development of social cognition. | | 8:15p |
Genetic editing of primary human dorsal root ganglion neurons using CRISPR-Cas9 with functional confirmation
CRISPR-Cas9 editing is now the leading method for genome editing and is being advanced for the treatment of human disease. CRIPSR editing could have many applications for treatment of neurological diseases, including pain but traditional viral vector delivery approaches have neurotoxicity limiting their use. Overcoming these issues could open the door for genome editing treatments for diseases like intractable pain where the dorsal root ganglia (DRG) would be the desired target. To this end, we describe a simple method for viral-vector-independent transfection of primary human DRG (hDRG) neurons for CRISPR-Cas9 editing. As proof of principle, we edited TRPV1, NTSR2, and CACNA1E using a lipofection method with CRISPR-Cas9 plasmids containing reporter tags (GFP or mCherry). Transfection was successful as demonstrated by the expression of the reporters as early as two days in vitro. CRISPR-Cas9 editing was confirmed at the genome level with insertion and deletion detection system T7-endonuclease-I assay; protein level with immunocytochemistry and Western blot; and functional level through capsaicin-induced Ca2+ accumulation in a high-throughput compatible fluorescent imaging plate reader (FLIPR) system. This work establishes a reliable, target specific, non-viral CRISPR-Cas9-mediated genetic editing in primary human neurons with potential for future clinical application for intractable pain.
TeaserWe describe a non-viral transfection method for CRISPR-Cas9 gene editing in human dorsal root ganglion neurons. | | 10:18p |
GLP1R agonists activate human POMC neurons
Drugs like Semaglutide (a.k.a. Ozempic/Wegovy) that activate the glucagon-like peptide-1 receptor (GLP1R) are a promising therapy for obesity and type 2 diabetes (T2D). Animal studies suggest that appetite-suppressing proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus are a likely target of these drugs, but the mechanisms by which they reduce food intake in humans are still unclear. We therefore generated POMC neurons from human pluripotent stem cells (hPSCs) to study their acute responses to GLP1R agonists by calcium imaging and electrophysiology. We found that hPSC-derived POMC neurons expressed GLP1R and many of them robustly responded to GLP1R agonists by membrane depolarization, increased action potential firing rate, and extracellular calcium influx that persisted long after agonist withdrawal and was likely mediated by L-type calcium channels. Prolonged administration of Semaglutide upregulated transcriptional pathways associated with cell survival in POMC neurons, and downregulated pathways associated with oxidative stress and neurodegeneration. These findings suggest that POMC neurons contribute to the long-term appetite-suppressive effects of GLP1R agonists in humans. |
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