scholarly journals Predicting how and when hidden neurons skew measured synaptic interactions

2017 ◽  
Author(s):  
Braden A. W. Brinkman ◽  
Fred Rieke ◽  
Eric Shea-Brown ◽  
Michael A. Buice
Keyword(s):  
Neural Coding ◽  
Neural Circuit ◽  
Quantitative Relationship ◽  
Network Size ◽  
Effective Interactions ◽  
Synaptic Interactions ◽  
Neural Computations ◽  
Hidden Neurons ◽  
Circuit Function ◽  
The Impact

AbstractA major obstacle to understanding neural coding and computation is the fact that experimental recordings typically sample only a small fraction of the neurons in a circuit. Measured neural properties are skewed by interactions between recorded neurons and the “hidden” portion of the network. To properly interpret neural data and determine how biological structure gives rise to neural circuit function, we thus need a better understanding of the relationships between measured effective neural properties and the true underlying physiological properties. Here, we focus on how the effective spatiotemporal dynamics of the synaptic interactions between neurons are reshaped by coupling to unobserved neurons. We find that the effective interactions from a pre-synaptic neuronr′to a post-synaptic neuronrcan be decomposed into a sum of the true interaction fromr′torplus corrections from every directed path fromr′torthrough unobserved neurons. Importantly, the resulting formula reveals when the hidden units have—or do not have—major effects on reshaping the interactions among observed neurons. As a particular example of interest, we derive a formula for the impact of hidden units in random networks with “strong” coupling—connection weights that scale with, whereNis the network size, precisely the scaling observed in recent experiments. With this quantitative relationship between measured and true interactions, we can study how network properties shape effective interactions, which properties are relevant for neural computations, and how to manipulate effective interactions.

scholarly journals Neural architecture: from cells to circuits

2018 ◽  
Vol 120 (2) ◽  
pp. 854-866 ◽  
Author(s):  
Sarah E. V. Richards ◽  
Stephen D. Van Hooser
Keyword(s):  
Nervous System ◽  
Cerebral Cortex ◽  
Structure Function ◽  
Neural Circuits ◽  
Neural Circuit ◽  
Neuronal Morphology ◽  
Neural Architecture ◽  
Synaptic Interactions ◽  
Branching Patterns ◽  
Circuit Function

Circuit operations are determined jointly by the properties of the circuit elements and the properties of the connections among these elements. In the nervous system, neurons exhibit diverse morphologies and branching patterns, allowing rich compartmentalization within individual cells and complex synaptic interactions among groups of cells. In this review, we summarize work detailing how neuronal morphology impacts neural circuit function. In particular, we consider example neurons in the retina, cerebral cortex, and the stomatogastric ganglion of crustaceans. We also explore molecular coregulators of morphology and circuit function to begin bridging the gap between molecular and systems approaches. By identifying motifs in different systems, we move closer to understanding the structure-function relationships that are present in neural circuits.

scholarly journals Neural circuit function redundancy in brain disorders

2021 ◽  
Vol 70 ◽  
pp. 74-80
Author(s):  
Beatriz E.P. Mizusaki ◽  
Cian O'Donnell
Keyword(s):  
Neural Circuit ◽  
Brain Disorders ◽  
Circuit Function

scholarly journals A visual circuit uses complementary mechanisms to support transient and sustained pupil constriction

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
William Thomas Keenan ◽  
Alan C Rupp ◽  
Rachel A Ross ◽  
Preethi Somasundaram ◽  
Suja Hiriyanna ◽  
...  
Keyword(s):  
Neural Coding ◽  
Pupil Size ◽  
Neural Circuit ◽  
Ganglion Cells ◽  
Retinal Ganglion ◽  
Neural Basis ◽  
Behavioral Dynamics ◽  
Pupil Constriction ◽  
Sustained Responses ◽  
Stable Control

Rapid and stable control of pupil size in response to light is critical for vision, but the neural coding mechanisms remain unclear. Here, we investigated the neural basis of pupil control by monitoring pupil size across time while manipulating each photoreceptor input or neurotransmitter output of intrinsically photosensitive retinal ganglion cells (ipRGCs), a critical relay in the control of pupil size. We show that transient and sustained pupil responses are mediated by distinct photoreceptors and neurotransmitters. Transient responses utilize input from rod photoreceptors and output by the classical neurotransmitter glutamate, but adapt within minutes. In contrast, sustained responses are dominated by non-conventional signaling mechanisms: melanopsin phototransduction in ipRGCs and output by the neuropeptide PACAP, which provide stable pupil maintenance across the day. These results highlight a temporal switch in the coding mechanisms of a neural circuit to support proper behavioral dynamics.

scholarly journals Zebrafish Dscaml1 is Essential for Retinal Patterning and Function of Oculomotor Subcircuits

2019 ◽  
Author(s):  
Manxiu Ma ◽  
Alexandro D. Ramirez ◽  
Tong Wang ◽  
Rachel L. Roberts ◽  
Katherine E. Harmon ◽  
...  
Keyword(s):  
Animal Model ◽  
Light Adaptation ◽  
Neural Circuit ◽  
Oculomotor System ◽  
Gaze Stabilization ◽  
Ocular Disorders ◽  
Motor Apraxia ◽  
Premotor Pathways ◽  
And Function ◽  
Circuit Function

AbstractDown Syndrome Cell Adhesion Molecules (dscam and dscaml1) are essential regulators of neural circuit assembly, but their roles in vertebrate neural circuit function are still mostly unexplored. We investigated the role of dscaml1 in the zebrafish oculomotor system, where behavior, circuit function, and neuronal activity can be precisely quantified. Loss of zebrafish dscaml1 resulted in deficits in retinal patterning and light adaptation, consistent with its known roles in mammals. Oculomotor analyses showed that mutants have abnormal gaze stabilization, impaired fixation, disconjugation, and faster fatigue. Notably, the saccade and fatigue phenotypes in dscaml1 mutants are reminiscent of human ocular motor apraxia, for which no animal model exists. Two-photon calcium imaging showed that loss of dscaml1 leads to impairment in the saccadic premotor pathway but not the pretectum-vestibular premotor pathway, indicating a subcircuit requirement for dscaml1. Together, we show that dscaml1 has both broad and specific roles in oculomotor circuit function, providing a new animal model to investigate the development of premotor pathways and their associated human ocular disorders.

scholarly journals Kappa-opioid receptor-dependent changes in dopamine and affective behavior occur differentially across the nucleus accumbens shell rostro-caudal axis

2020 ◽  
Author(s):  
Breanne E. Pirino ◽  
Mary B. Spodnick ◽  
Andrew T. Gargiulo ◽  
Genevieve R. Curtis ◽  
Jessica R. Barson ◽  
...  
Keyword(s):  
Nucleus Accumbens ◽  
Opioid Receptor ◽  
Dopamine Release ◽  
Neural Circuit ◽  
Ex Vivo ◽  
Kappa Opioid Receptor ◽  
Affective Behavior ◽  
Kappa Opioid ◽  
Affective Behaviors ◽  
The Impact

ABSTRACTNeural circuit engagement within the nucleus accumbens (NAc) shell is implicated in the regulation of both negative and positive affect. Classically, the dynorphin/kappa opioid receptor (KOR) system in the NAc was believed to promote dysphoric behavior, while dopamine was viewed as interacting with reward behavior, and KOR activation was known to inhibit dopamine release. Recently, however, both the KOR and dopamine systems have, separately, been shown to have differential effects across the rostro-caudal axis of the NAc shell on hedonic responses. Whether or not this is due to interactions between KORs and dopamine, and if it extends to other affective behaviors, remains to be determined. In this study, we examined in rats the relationship between the KOR and dopamine systems in both the rostral and caudal NAc shell using ex vivo fast scan cyclic voltammetry and the impact of KOR activation on affective behavior using approach-avoidance assays. We report here that activation of KORs in the caudal NAc shell significantly inhibits dopamine release, stimulates novelty-induced rearing behavior, increases avoidance behavior, and reduces locomotor activity. In contrast, activation of KORs in the rostral NAc shell inhibits dopamine release to a lesser extent and instead increases approach behavior. Taken together, these results indicate that there is heterogeneity across the rostro-caudal axis of the NAc shell in the effects of KOR stimulation on affective behaviors, and they suggest that this might be due to differences in KOR control over dopamine release.

scholarly journals Quantitative synapse analysis for cell-type specific connectomics

2018 ◽  
Author(s):  
Dika A. Kuljis ◽  
Khaled Zemoura ◽  
Cheryl A. Telmer ◽  
Jiseok Lee ◽  
Eunsol Park ◽  
...  
Keyword(s):  
Large Scale ◽  
Neural Circuit ◽  
Apical Dendrite ◽  
Automated Detection ◽  
Cell Type ◽  
Disease States ◽  
Specific Localization ◽  
Cell Type Specific ◽  
Dendritic Branches ◽  
Circuit Function

AbstractAnatomical methods for determining cell-type specific connectivity are essential to inspire and constrain our understanding of neural circuit function. We developed new genetically-encoded reagents for fluorescence-synapse labeling and connectivity analysis in brain tissue, using a fluorogen-activating protein (FAP)-or YFP-coupled, postsynaptically-localized neuroligin-1 targeting sequence (FAP/YFPpost). Sparse viral expression of FAP/YFPpost with the cell-filling, red fluorophore dTomato (dTom) enabled high-throughput, compartment-specific localization of synapses across diverse neuron types in mouse somatosensory cortex. High-resolution confocal image stacks of virally-transduced neurons were used for 3D reconstructions of postsynaptic cells and automated detection of synaptic puncta. We took advantage of the bright, far-red emission of FAPpost puncta for multichannel fluorescence alignment of dendrites, synapses, and presynaptic neurites to assess subtype-specific inhibitory connectivity onto L2 neocortical pyramidal (Pyr) neurons. Quantitative and compartment-specific comparisons show that PV inputs are the dominant source of inhibition at both the soma and across all dendritic branches examined and were particularly concentrated at the primary apical dendrite, a previously unrecognized compartment of L2 Pyr neurons. Our fluorescence-based synapse labeling reagents will facilitate large-scale and cell-type specific quantitation of changes in synaptic connectivity across development, learning, and disease states.

Strain and electric field tunable photoelectric properties of multilayer Sb2Se3

2021 ◽  
Author(s):  
Wanxin Ding ◽  
Longhua Li
Keyword(s):  
Electric Field ◽  
Band Gap ◽  
Quantitative Relationship ◽  
Uniaxial Strain ◽  
Strain Property ◽  
Photovoltaic Properties ◽  
Electric Field Sensors ◽  
Photoelectric Properties ◽  
Photovoltaic Parameters ◽  
The Impact

Abstract Antimony selenide, Sb2Se3, has been attracted widespread attention in photovoltaic applications due to its high absorption coefficient and suitable band gap. However, the influence of uniaxial strain and electric field on the electronic and photovoltaic properties of multilayer Sb2Se3 is still unknown. Here, the quantitative relationship, such as strain-property, electric field-property, as well as thickness-property, is explored via first-principles calculations. Our results demonstrate that the band gap and photovoltaic parameters (Jsc, Voc, FF and PCE) of multilayer Sb2Se3 are not only affected by the uniaxial strain and electric field, but can also be tuned via the coupling of thickness with strain and electric field. The band-gap of multilayer Sb2Se3 is linear dependent on uniaxial strain and external electric field. We found that the effect of strain on the photovoltaic parameters could be negligible as compared with the effect of thickness. However, the effect of electric field is thickness dependent, 1 ‒ 2 layer(s) thin films are not affected while the impact of electric field increases with the increasing thickness. The quantitative strain (electric field)-properties relation of multilayer Sb2Se3 suggesting that Sb2Se3 films have a potential application in the field of strain and electric field sensors.

Test Bench for Characterization and Design Against Steam Turbine Fouling

2021 ◽  
Author(s):  
Gabriele Girezzi ◽  
Damaso Checcacci ◽  
Lorenzo Cosi ◽  
Andrea Maggi ◽  
Alessandro Sani ◽  
...  
Keyword(s):  
Test Bench ◽  
Quantitative Relationship ◽  
Industrial Applications ◽  
Inlet Section ◽  
Steam Turbines ◽  
Steam Quality ◽  
Power Utility ◽  
Large Power ◽  
Thermodynamic Conditions ◽  
The Impact

Abstract The fouling phenomenon addressed in this paper is related to the deposition within steam turbines of steam impurities and to the presence of solid debris, coming from upstream plant sections, that can create solid build-ups in stationary and moving parts inside the turbine. As a consequence, fouling causes unit efficiency decline but, in severe cases, it may also lead to sticking of moving components, such as valves, that may be critical in machine control and/or safety. Despite well-studied and well-considered in design and operation of large power utility plants, where steam quality is of primary importance for boilers, super-heaters, turbines and condensers, this subject is often overlooked in small power generation or industrial applications, where efficiency may be less critical but turbine availability is of paramount importance for plant operation (e.g. LNG plants). The steam fouling is a subject that, despite widely studied in the past, has been quite neglected in more recent years. This paper, with the aim of underlining the importance of fouling in the operation of turbines for industrial applications, starts with examples of field evidences of severe fouling. Then the design of a test bench for the experimental characterization of fouling rates and validation of turbine components, exposed to fouling conditions, is presented along with the description of the deposition models that were developed on the basis of the physical phenomena involved in the fouling process. This study addresses the main deposition physical principles and their implications in the thermodynamic design of the test bench, on the basis of the specific physical properties of the impurities of interest. To better match plant real cases, the contaminants tested included those which have been usually identified within the units during maintenance activities and for which specific limits are prescribed by OEMs. In the following section, details relevant to the main deposition mechanisms due to different geometries and flow-fields are discussed. The results obtained are qualitatively in line with literature and internal practices, yet, through the test activities, it has been possible to establish a quantitative relationship between the concentrations of each contaminant at inlet section and the different thermodynamic conditions along the test bench, so capturing the impact of solubility changes along with the steam expansion.

scholarly journals Rapid and sustained homeostatic control of presynaptic exocytosis at a central synapse

2019 ◽  
Vol 116 (47) ◽  
pp. 23783-23789 ◽  
Author(s):  
Igor Delvendahl ◽  
Katarzyna Kita ◽  
Martin Müller
Keyword(s):  
Time Scales ◽  
Neural Circuit ◽  
Mossy Fiber ◽  
Pool Size ◽  
Homeostatic Plasticity ◽  
Experimental Conditions ◽  
Central Synapse ◽  
Circuit Function ◽  
Vesicle Pool ◽  
Activity Dependent

Animal behavior is remarkably robust despite constant changes in neural activity. Homeostatic plasticity stabilizes central nervous system (CNS) function on time scales of hours to days. If and how CNS function is stabilized on more rapid time scales remains unknown. Here, we discovered that mossy fiber synapses in the mouse cerebellum homeostatically control synaptic efficacy within minutes after pharmacological glutamate receptor impairment. This rapid form of homeostatic plasticity is expressed presynaptically. We show that modulations of readily releasable vesicle pool size and release probability normalize synaptic strength in a hierarchical fashion upon acute pharmacological and prolonged genetic receptor perturbation. Presynaptic membrane capacitance measurements directly demonstrate regulation of vesicle pool size upon receptor impairment. Moreover, presynaptic voltage-clamp analysis revealed increased Ca2+-current density under specific experimental conditions. Thus, homeostatic modulation of presynaptic exocytosis through specific mechanisms stabilizes synaptic transmission in a CNS circuit on time scales ranging from minutes to months. Rapid presynaptic homeostatic plasticity may ensure stable neural circuit function in light of rapid activity-dependent plasticity.

scholarly journals Dam Effects on Downstream Riparian Wetlands: The Nenjiang River, Northeast China

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2038 ◽  
Author(s):  
Yuexin Zheng ◽  
Guangxin Zhang ◽  
Yanfeng Wu ◽  
Y. Jun Xu ◽  
Changlei Dai
Keyword(s):  
Northeast China ◽  
Quantitative Relationship ◽  
Flood Frequency ◽  
Stepwise Multiple Regression ◽  
Distribution Data ◽  
Dam Construction ◽  
Riparian Wetlands ◽  
Transport Channel ◽  
Riparian Wetland ◽  
The Impact

Many studies have found that damming a river can change downstream hydrology, sediment transport, channel morphology, and fish habitat. However, little is known about river dam effects on downstream riparian wetland dynamics and their quantitative relationship with hydrological alterations. In this study, hydrological time series and wetland distribution data spanning nearly 40 years (1978–2016) before and after the construction of a large dam in 2005 across the Nenjiang River in Northeast China were used to reveal the impact of dam on the downstream discharge regime and wetland degradation. Hydro-statistical and stepwise multiple regression analyses were performed to quantify the relationship of riparian wetland area with a metrics of 33 hydrological indicators. Dam construction caused decline in peak discharge, flood frequency, and magnitude. Moreover, 150 km riparian wetlands along the downstream of the dam was largely reduced. The count and duration of high flow pulses, 1-day maximum, and date of maximum discharge changed significantly after the dam construction. The hydrological changes have made a significant contribution to the 44% reduction in riparian wetlands following the dam construction. Our results indicated that hydrological alterations caused by dam regulation led to the area reduction of downstream riparian wetlands. The findings provide relevant information for developing best dam operation practices to protect and restore downstream wetland ecosystems.

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