Glycoprotein-deleted (ΔG) rabies virus is a powerful tool for studies of neural circuit structure. Here, we describe the development and demonstrate the utility of new resources that allow ...experiments directly investigating relationships between the structure and function of neural circuits. New methods and reagents allowed efficient production of 12 novel ΔG rabies variants from plasmid DNA. These new rabies viruses express useful neuroscience tools, including the Ca2+ indicator GCaMP3 for monitoring activity; Channelrhodopsin-2 for photoactivation; allatostatin receptor for inactivation by ligand application; and rtTA, ERT2CreERT2, or FLPo, for control of gene expression. These new tools allow neurons targeted on the basis of their connectivity to have their function assayed or their activity or gene expression manipulated. Combining these tools with in vivo imaging and optogenetic methods and/or inducible gene expression in transgenic mice will facilitate experiments investigating neural circuit development, plasticity, and function that have not been possible with existing reagents.
► New methods allowed efficient production of ΔG rabies viruses from plasmid DNA ► Twelve new rabies variants express useful genetically-encoded neuroscience tools ► Encoded genes monitor or control activity or gene expression in defined circuits ► These reagents facilitate studies directly linking circuit structure to function
The hypothalamic neuropeptide oxytocin (OT), which controls childbirth and lactation, receives increasing attention for its effects on social behaviors, but how it reaches central brain regions is ...still unclear. Here we gained by recombinant viruses selective genetic access to hypothalamic OT neurons to study their connectivity and control their activity by optogenetic means. We found axons of hypothalamic OT neurons in the majority of forebrain regions, including the central amygdala (CeA), a structure critically involved in OT-mediated fear suppression. In vitro, exposure to blue light of channelrhodopsin-2-expressing OT axons activated a local GABAergic circuit that inhibited neurons in the output region of the CeA. Remarkably, in vivo, local blue-light-induced endogenous OT release robustly decreased freezing responses in fear-conditioned rats. Our results thus show widespread central projections of hypothalamic OT neurons and demonstrate that OT release from local axonal endings can specifically control region-associated behaviors.
► We constructed a virus to express any protein, e.g., ChR2, only in oxytocin neurons ► Fluorescent oxytocin neurons project simultaneously to the forebrain and pituitary ► Blue-light exposure of oxytocin axons in vitro affects amygdala neuronal activity ► Blue-light amygdala exposure in vivo evokes oxytocin-mediated decreases in fear
To address the role of the hypothalamic oxytocin (OT)-expressing neurons, Knobloch et al. expressed channelrhodopsin-2 in these neurons. OT neurons project to the central amygdala, as well as other forebrain regions, and activation of these neurons induced oxytocin release and freezing responses in fear-conditioned rats.
Normalization has been proposed as a canonical computation that accounts for a variety of nonlinear neuronal response properties associated with sensory processing and higher cognitive functions. A ...key premise of normalization is that the excitability of a neuron is inversely proportional to the overall activity level of the network. We tested this by optogenetically activating excitatory neurons in alert macaque primary visual cortex and measuring changes in neuronal activity as a function of stimulation intensity, with or without variable-contrast visual stimulation. Optogenetic depolarization of excitatory neurons either facilitated or suppressed baseline activity, consistent with indirect recruitment of inhibitory networks. As predicted by the normalization model, neurons exhibited sub-additive responses to optogenetic and visual stimulation, which depended lawfully on stimulation intensity and luminance contrast. We conclude that the normalization computation persists even under the artificial conditions of optogenetic stimulation, underscoring the canonical nature of this form of neural computation.
•Optogenetic depolarization of excitatory neurons activates normalization in V1•Activated circuits mediate competition between optogenetic and visual stimulation•This competition can be biased by elevating the intensity of each stimulus•The normalization model provides excellent fits to these stimulus interactions
The Normalization Model can account for a wide variety of neural computations, ranging from contrast gain control to attentional selection. Here, Nassi et al. find strong support for the model by combining optogenetic and visual stimulation in primate visual cortex.
The effects of crystallization time and amount of Zeolitic Imidazolate Framework-8 (ZIF-8) on the photocatalytic activity of ZIF-8 decorated copper (Cu) doped titania (TiO2) (ZIF-8/Cu-TiO2) powders ...were investigated in this study. The formation of nanocomposite structure of ZIF-8 crystals grown over the surface of core Cu-TiO2 particles containing heterojunction sites was observed at low ZIF-8 level. Powders containing ZIF-8 in the 5–46% range (weight basis) were synthesized and their activities in the photocatalytic degradation of an organic dye molecule were evaluated. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (ATR-FTIR), thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HR-TEM) analyses indicated that ZIF-8/Cu-TiO2 nanocomposite can be prepared at low levels of ZIF-8. HR-TEM images of 46% ZIF-8/Cu-TiO2 showed that Cu-TiO2 particles act as a core and ZIF-8 crystals grow over the surface of Cu-TiO2 particles during crystal growth and Cu-TiO2 particles were almost completely covered with ZIF-8 crystals. Photocatalytic activity increased with decreasing ZIF-8 level which was attributed to the formation of heterojunctions due to partial coverage of TiO2 surface. The 1st order reaction rate constant of ZIF-8/Cu-TiO2 nanocomposite containing 5% ZIF-8 was found to be 4 and 1.4 times that of bare ZIF-8 and Cu-TiO2, respectively. Partial coverage of TiO2 surface with ZIF-8 crystals lead to the formation of light exposed ZIF-8/Cu-TiO2 heterojunction sites for the enhanced degradation of the dye molecule. The presence of ZIF-8 in the nanocomposite also increased the adsorption of the organic dye by the interaction with open Zn2+ metal sites of ZIF-8 on the nanocomposite surface. This study revealed that ZIF-8/Cu-TiO2 nanocomposites could be prepared at low ZIF-8 levels and short growth times with higher photocatalytic activities than their constituents and nanocomposites prepared at higher ZIF-8 levels and longer growth times.
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•ZIF-8/Cu-TiO2 heterojunction occurred at low ZIF-8 levels.•ZIF-8 in the ZIF-8/Cu-TiO2 nanocomposite increased dye adsorption capacity.•ZIF-8/Cu-TiO2 heterojunction enhanced charge carrier separation.•ZIF-8/Cu-TiO2 showed higher photocatalytic activity than Cu-TiO2 and ZIF-8.
The k-nearest neighbors (k-NN) algorithm, a fundamental machine learning technique, typically employs the Euclidean distance metric for proximity-based data classification. This research focuses on ...the feature importance infused k-NN model, an advanced form of k-NN. Diverging from traditional algorithm uniform weighted Euclidean distance, feature importance infused k-NN introduces a specialized distance weighting system. This system emphasizes critical features while reducing the impact of lesser ones, thereby enhancing classification accuracy. Empirical studies indicate a 1.7% average accuracy improvement with proposed model over conventional model, attributed to its effective handling of feature importance in distance calculations. Notably, a significant positive correlation was observed between the disparity in feature importance levels and the model's accuracy, highlighting proposed model?s proficiency in handling variables with limited explanatory power. These findings suggest proposed model?s potential and open avenues for future research, particularly in refining its feature importance weighting mechanism, broadening dataset applicability, and examining its compatibility with different distance metrics.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Rapid cell type identification by new genomic single-cell analysis methods has not been met with efficient experimental access to these cell types. To facilitate access to specific neural populations ...in mouse cortex, we collected chromatin accessibility data from individual cells and identified enhancers specific for cell subclasses and types. When cloned into recombinant adeno-associated viruses (AAVs) and delivered to the brain, these enhancers drive transgene expression in specific cortical cell subclasses. We extensively characterized several enhancer AAVs to show that they label different projection neuron subclasses as well as a homologous neuron subclass in human cortical slices. We also show how coupling enhancer viruses expressing recombinases to a newly generated transgenic mouse, Ai213, enables strong labeling of three different neuronal classes/subclasses in the brain of a single transgenic animal. This approach combines unprecedented flexibility with specificity for investigation of cell types in the mouse brain and beyond.
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•High-quality single-cell ATAC-seq dataset for adult mouse visual cortex•Enhancer AAVs targeting distinct subclasses of excitatory projection neurons•New TIGRE-based transgenic reporter line with three-color readout•Combined enhancer AAVs label up to three distinct cell populations in one brain
Graybuck et al. generated a single-cell chromatin accessibility dataset for adult mouse cortex and identified functional enhancer elements. They created a suite of enhancer-containing adeno-associated viruses to label genetically defined cell populations in the mouse brain.
Type 1 estrogen receptor-expressing neurons in the ventrolateral subdivision of the ventromedial hypothalamus (VMHvlEsr1) play a causal role in the control of social behaviors, including aggression. ...Here we use six different viral-genetic tracing methods to systematically map the connectional architecture of VMHvlEsr1 neurons. These data reveal a high level of input convergence and output divergence (“fan-in/fan-out”) from and to over 30 distinct brain regions, with a high degree (∼90%) of bidirectionality, including both direct as well as indirect feedback. Unbiased collateralization mapping experiments indicate that VMHvlEsr1 neurons project to multiple targets. However, we identify two anatomically distinct subpopulations with anterior vs. posterior biases in their collateralization targets. Nevertheless, these two subpopulations receive indistinguishable inputs. These studies suggest an overall system architecture in which an anatomically feed-forward sensory-to-motor processing stream is integrated with a dense, highly recurrent central processing circuit. This architecture differs from the “brain-inspired,” hierarchical feed-forward circuits used in certain types of artificial intelligence networks.
Background: Spontaneous pneumomediastinum (SPM) is a rare and benign self-limiting condition characterized by the presence of air in the mediastinum without an apparent cause. Boerhaave syndrome, on ...the other hand, is a rare condition caused by spontaneous esophageal perforation due to severe vomiting. The mediastinum is a complex anatomical region housing vital organs, making clinical comprehension challenging. Objectives: There is no established approach to diagnosing and treating children with SPM. Despite similarities in the presence of air in the mediastinum, SPM and Boerhaave syndrome are distinct entities. However, the primary challenge for patients is ruling out esophageal perforation. We aimed to highlight this rare issue by presenting the results of our patient series to guide further examination in pediatric patients with mediastinal air. Methods: We included twenty-four pediatric patients diagnosed with SPM between 2014 and 2022. Demographic and clinical characteristics, diagnostic procedures, treatments, and follow-up details were retrospectively recorded. Results: The mean age of the twenty male and four female patients was 14 years. Common triggers included coughing (45%), increased physical exertion (33%), and retching/vomiting (8%). All patients experienced chest pain, with additional symptoms such as dyspnea (50%), neck pain (30%), and dysphagia (12%). Symptoms resolved within two days of hospitalization. Patients were often misdiagnosed and received inappropriate treatment at other centers before being transferred to our hospital. A fluoroscopic esophagogram conducted within an average of 22 hours from admission revealed no abnormalities. Oral feeding was withheld for an average of 28 hours. The mean duration of symptom-free hospitalization without treatment was 32 hours. Conclusions: It appears that emergency department physicians may lack familiarity with pneumomediastinum. Surgeons' concerns about missing Boerhaave's syndrome may lead to unnecessary tests, prolonged fasting, and hospital stays for patients with SPM.
Background: Cortical inhibition plays a critical role in controlling and modulating cortical excitation, and a more detailed understanding of the neuronal circuits contributing to each will provide ...more insight into their roles in complex cortical computations. Traditional neuronal tracers lack a means for easily distinguishing between circuits of inhibitory and excitatory neurons. To overcome this limitation, we have developed a technique for retrogradely labeling inputs to local clusters of inhibitory or excitatory neurons, but not both, using neurotropic adenoassociated and lentiviral vectors, cell-type-specific promoters, and a modified rabies virus.
Results: Applied to primary visual cortex (V1) in mouse, the cell-type-specific tracing technique labeled thousands of presynaptically connected neurons and revealed that the dominant source of input to inhibitory and excitatory neurons is local in origin. Neurons in other visual areas are also labeled; the percentage of these intercortical inputs to excitatory neurons is somewhat higher (∼20%) than to inhibitory neurons (<10%), suggesting that intercortical connections have less direct control over inhibition. The inputs to inhibitory neurons were also traced in cat V1, and when aligned with the orientation preference map revealed for the first time that long-range inputs to inhibitory neurons are well tuned to orientation.
Conclusions: These novel findings for inhibitory and excitatory circuits in the visual cortex demonstrate the efficacy of our new technique and its ability to work across species, including larger-brained mammals such as the cat. This paves the way for a better understanding of the roles of specific cell types in higher-order perceptual and cognitive processes.
•Cell-type-specific gene delivery is achieved through viral vector/promoter design•Gene expression targets rabies to trace inputs to inhibitory or excitatory neurons•Inhibitory neurons in V1 receive fewer feedback inputs than excitatory neurons•Intrinsic inputs to inhibitory V1 neurons are tuned to orientation preference
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