scholarly journals Transient inhibition to light explains stronger V1 responses to dark stimuli

2021 ◽  
Author(s):  
David St-Amand ◽  
Curtis L Baker
Keyword(s):  
Cortical Neurons ◽  
Natural Image ◽  
Simple Type ◽  
Neuronal Responses ◽  
Biologically Inspired ◽  
V1 Neurons ◽  
Novel Approach ◽  
Electrophysiological Responses ◽  
Light Stimuli ◽  
Insight Into

Neurons in the primary visual cortex (V1) receive excitation and inhibition from two different pathways processing lightness (ON) and darkness (OFF). V1 neurons overall respond more strongly to dark than light stimuli (Yeh, Xing and Shapley, 2010; Kremkow et al., 2014), consistent with a preponderance of darker regions in natural images (Ratliff et al., 2010), as well as human psychophysics (Buchner & Baumgartner, 2007). However, it has been unclear whether this "dark-dominance" is due to more excitation from the OFF pathway (Jin et al., 2008) or more inhibition from the ON pathway (Taylor et al., 2018). To understand the mechanisms behind dark-dominance, we record electrophysiological responses of individual simple-type V1 neurons to natural image stimuli and then train biologically inspired convolutional neural networks to predict the neuronal responses. Analyzing a sample of 74 neurons (in anesthetized, paralyzed cats) has revealed their responses to be more driven by dark than light stimuli, consistent with previous investigations (Yeh et al., 2010; Kremkow et al., 2013). We show this asymmetry to be predominantly due to slower inhibition to dark stimuli rather than by stronger excitation from the thalamocortical OFF pathway. Consistent with dark-dominant neurons having faster responses than light-dominant neurons (Komban et al., 2014), we find dark-dominance to solely occur in the early latencies of neuronal responses. Neurons that are strongly dark-dominated also tend to be less orientation selective. This novel approach gives us new insight into the dark-dominance phenomenon and provides an avenue to address new questions about excitatory and inhibitory integration in cortical neurons.

scholarly journals Current models cannot account for V1's specialisation for binocular natural image statistics

2018 ◽  
Author(s):  
Sid Henriksen ◽  
Daniel A Butts ◽  
Jenny C. A. Read ◽  
Bruce G Cumming
Keyword(s):  
Nonlinear Models ◽  
General Linear ◽  
Natural Image ◽  
Natural Image Statistics ◽  
Neuronal Responses ◽  
Strong Response ◽  
Image Statistics ◽  
Systems Neuroscience ◽  
V1 Neurons ◽  
Optimisation Techniques

A long-standing observation about primary visual cortex (V1) is that the stimulus selectivity of neurons can be well explained with a cascade of linear computations followed by a nonlinear rectification stage. This framework remains highly influential in systems neuroscience and has also inspired recent efforts in artificial intelligence. The success of these models include describing the disparity-selectivity of binocular neurons in V1. Some aspects of real neuronal disparity responses are hard to explain with simple linear-nonlinear models, notably the attenuated response of real cells to "anticorrelated" stimuli which violate natural binocular image statistics. General linear-nonlinear models can account for this attenuation, but no one has yet tested whether they quantitatively match the response of real neurons. Here, we exhaustively test this framework using recently developed optimisation techniques. We show that many cells are very poorly characterised by even general linear-nonlinear models. Strikingly, the models can account for neuronal responses to unnatural anticorrelated stimuli as well as to most natural, correlated stimuli. However, the models fail to capture the particularly strong response to binocularly correlated stimuli at the preferred disparity of the cell. Thus, V1 neurons perform an amplification of responses to correlated stimuli which cannot be accounted for by a linear-nonlinear cascade. The implication is that even simple stimulus selectivity in V1 requires more complex computations than previously envisaged.

Anodic stripping voltammetry of anti-Vi antibody functionalized CdTe quantum dots for the specific monitoring of Salmonella enterica serovar Typhi

RSC Advances ◽  
2015 ◽  
Vol 5 (107) ◽  
pp. 88234-88240 ◽  
Author(s):  
Satish K. Pandey ◽  
Praveen Rishi ◽  
C. Raman Suri ◽  
Aaydha C. Vinayaka
Keyword(s):  
Quantum Dots ◽  
Capsular Polysaccharide ◽  
Anodic Stripping Voltammetry ◽  
Stripping Voltammetry ◽  
Cdte Quantum Dots ◽  
Salmonella Enterica Serovar Typhi ◽  
Novel Approach ◽  
Anodic Stripping ◽  
Vi Capsular Polysaccharide ◽  
Insight Into

CdTe QD based stripping voltammetry for Vi capsular polysaccharide detection. The technique has provided an insight into the competence of CdTe QD and GNP immuno-conjugates. This is a novel approach to characterize the efficiency of immuno-conjugates of QDs and GNPs.

scholarly journals Attention operates uniformly throughout the classical receptive field and the surround

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Bram-Ernst Verhoef ◽  
John HR Maunsell
Keyword(s):  
Receptive Field ◽  
Cortical Neurons ◽  
Receptive Fields ◽  
Spatial Summation ◽  
Field Structure ◽  
Neuronal Responses ◽  
Large Variability ◽  
Area V4 ◽  
Classical Receptive Field ◽  
Spatially Varying

Shifting attention among visual stimuli at different locations modulates neuronal responses in heterogeneous ways, depending on where those stimuli lie within the receptive fields of neurons. Yet how attention interacts with the receptive-field structure of cortical neurons remains unclear. We measured neuronal responses in area V4 while monkeys shifted their attention among stimuli placed in different locations within and around neuronal receptive fields. We found that attention interacts uniformly with the spatially-varying excitation and suppression associated with the receptive field. This interaction explained the large variability in attention modulation across neurons, and a non-additive relationship among stimulus selectivity, stimulus-induced suppression and attention modulation that has not been previously described. A spatially-tuned normalization model precisely accounted for all observed attention modulations and for the spatial summation properties of neurons. These results provide a unified account of spatial summation and attention-related modulation across both the classical receptive field and the surround.

Envelope wages as a new normal? An insight into a pool of prospective quasi-formal workers in the European Union (EU)

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Josip Franic ◽  
Stanislaw Cichocki
Keyword(s):  
European Union ◽  
Pension System ◽  
Older Individuals ◽  
The European Union ◽  
Content Type ◽  
Random Intercept ◽  
Novel Approach ◽  
Wage Earners ◽  
Insight Into

PurposeIn spite of millions of quasi-formal workers in the European Union (EU), there is still limited understanding of what motivates workers to participate in these detrimental employment schemes, and why certain groups of workers exhibit higher inclination towards it. This article takes a novel approach by putting prospective envelope wage earners in the centre of this analysis.Design/methodology/approachData from the 2019 Special Eurobarometer on undeclared work are used, and two-level random intercept cumulative logit modelling is applied.FindingsOne in seven fully declared EU workers would have nothing against receiving one part of their wages off-the-books. Manual workers and individuals whose job assumes travelling are the most willing to accept such kind of remuneration, and the same applies to workers with low tax morale and those who perceive the risk of being detected and persecuted as very small. On the other hand, women, older individuals, married persons and employees from large enterprises express the smallest inclination towards envelope wages. The environment in which an individual operates also plays a non-negligible role as the quality of the pension system and the strength of social contract were also identified as significant determinants of workers' readiness to accept envelope wages.Originality/valueThis article fills in the gap in the literature by analysing what workers think about wage under-reporting and what factors drive their willingness to accept envelope wages.

scholarly journals Dysregulated Pyrimidine Biosynthesis Contributes to 5-FU Resistance in SCLC Patient-Derived Organoids but Response to a Novel Polymeric Fluoropyrimidine, CF10

Cancers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 788 ◽  
Author(s):  
William H. Gmeiner ◽  
Lance D. Miller ◽  
Jeff W. Chou ◽  
Anthony Dominijanni ◽  
Lysette Mutkus ◽  
...  
Keyword(s):  
Drug Target ◽  
Pyrimidine Biosynthesis ◽  
Cancer Drug ◽  
Rna Seq ◽  
Novel Approach ◽  
Anti Cancer ◽  
New Treatments ◽  
Insight Into ◽  
Sclc Patient ◽  
Identify Gene Expression

Chemo-immunotherapy is central to the treatment of small cell lung cancer (SCLC). Despite modest progress made with the addition of immunotherapy, current cytotoxic regimens display minimal survival benefit and new treatments are needed. Thymidylate synthase (TS) is a well-validated anti-cancer drug target, but conventional TS inhibitors display limited clinical efficacy in refractory or recurrent SCLC. We performed RNA-Seq analysis to identify gene expression changes in SCLC biopsy samples to provide mechanistic insight into the potential utility of targeting pyrimidine biosynthesis to treat SCLC. We identified systematic dysregulation of pyrimidine biosynthesis, including elevated TYMS expression that likely contributes to the lack of efficacy for current TS inhibitors in SCLC. We also identified E2F1-3 upregulation in SCLC as a potential driver of TYMS expression that may contribute to tumor aggressiveness. To test if TS inhibition could be a viable strategy for SCLC treatment, we developed patient-derived organoids (PDOs) from human SCLC biopsy samples and used these to evaluate both conventional fluoropyrimidine drugs (e.g., 5-fluorouracil), platinum-based drugs, and CF10, a novel fluoropyrimidine polymer with enhanced TS inhibition activity. PDOs were relatively resistant to 5-FU and while moderately sensitive to the front-line agent cisplatin, were relatively more sensitive to CF10. Our studies demonstrate dysregulated pyrimidine biosynthesis contributes to drug resistance in SCLC and indicate that a novel approach to target these pathways may improve outcomes.

Adaptation and Temporal Decorrelation by Single Neurons in the Primary Visual Cortex

2003 ◽  
Vol 89 (6) ◽  
pp. 3279-3293 ◽  
Author(s):  
Xiao-Jing Wang ◽  
Yinghui Liu ◽  
Maria V. Sanchez-Vives ◽  
David A. McCormick
Keyword(s):  
Cortical Neurons ◽  
Neural Coding ◽  
Model Neuron ◽  
Ionic Currents ◽  
Cellular Mechanism ◽  
Membrane Properties ◽  
Sensory Inputs ◽  
V1 Neurons ◽  
Temporal Correlations ◽  
Temporal Decorrelation

Limiting redundancy in the real-world sensory inputs is of obvious benefit for efficient neural coding, but little is known about how this may be accomplished by biophysical neural mechanisms. One possible cellular mechanism is through adaptation to relatively constant inputs. Recent investigations in primary visual (V1) cortical neurons have demonstrated that adaptation to prolonged changes in stimulus contrast is mediated in part through intrinsic ionic currents, a Ca2+-activated K+ current ( IKCa) and especially a Na+-activated K+ current ( IKNa). The present study was designed to test the hypothesis that the activation of adaptation ionic currents may provide a cellular mechanism for temporal decorrelation in V1. A conductance-based neuron model was simulated, which included an IKCa and an IKNa. We show that the model neuron reproduces the adaptive behavior of V1 neurons in response to high contrast inputs. When the stimulus is stochastic with 1/ f 2 or 1/ f-type temporal correlations, these autocorrelations are greatly reduced in the output spike train of the model neuron. The IKCa is effective at reducing positive temporal correlations at approximately 100-ms time scale, while a slower adaptation mediated by IKNa is effective in reducing temporal correlations over the range of 1–20 s. Intracellular injection of stochastic currents into layer 2/3 and 4 (pyramidal and stellate) neurons in ferret primary visual cortical slices revealed neuronal responses that exhibited temporal decorrelation in similarity with the model. Enhancing the slow afterhyperpolarization resulted in a strengthening of the decorrelation effect. These results demonstrate the intrinsic membrane properties of neocortical neurons provide a mechanism for decorrelation of sensory inputs.

scholarly journals Poly-arginine-18 (R18) Confers Neuroprotection through Glutamate Receptor Modulation, Intracellular Calcium Reduction, and Preservation of Mitochondrial Function

Molecules ◽  
2020 ◽  
Vol 25 (13) ◽  
pp. 2977
Author(s):  
Gabriella MacDougall ◽  
Ryan S. Anderton ◽  
Amy Trimble ◽  
Frank L. Mastaglia ◽  
Neville W. Knuckey ◽  
...  
Keyword(s):  
Intracellular Calcium ◽  
Glutamate Receptor ◽  
Cortical Neurons ◽  
Calcium Influx ◽  
Ros Generation ◽  
Neuronal Cultures ◽  
Atp Production ◽  
Endoplasmic Reticulum Calcium ◽  
Receptor Modulation ◽  
Insight Into

Recent studies have highlighted that a novel class of neuroprotective peptide, known as cationic arginine-rich peptides (CARPs), have intrinsic neuroprotective properties and are particularly effective anti-excitotoxic agents. As such, the present study investigated the mechanisms underlying the anti-excitotoxic properties of CARPs, using poly-arginine-18 (R18; 18-mer of arginine) as a representative peptide. Cortical neuronal cultures subjected to glutamic acid excitotoxicity were used to assess the effects of R18 on ionotropic glutamate receptor (iGluR)-mediated intracellular calcium influx, and its ability to reduce neuronal injury from raised intracellular calcium levels after inhibition of endoplasmic reticulum calcium uptake by thapsigargin. The results indicate that R18 significantly reduces calcium influx by suppressing iGluR overactivation, and results in preservation of mitochondrial membrane potential (ΔΨm) and ATP production, and reduced ROS generation. R18 also protected cortical neurons against thapsigargin-induced neurotoxicity, which indicates that the peptide helps maintain neuronal survival when intracellular calcium levels are elevated. Taken together, these findings provide important insight into the mechanisms of action of R18, supporting its potential application as a neuroprotective therapeutic for acute and chronic neurological disorders.

scholarly journals Application Search in Solution-Driven Biologically Inspired Design

2019 ◽  
Vol 1 (1) ◽  
pp. 269-278
Author(s):  
Torben Anker Lenau
Keyword(s):  
Design Methodology ◽  
The Self ◽  
Specific Production ◽  
Biologically Inspired ◽  
Technical Application ◽  
Coating Methods ◽  
Biologically Inspired Design ◽  
New Applications ◽  
A Company ◽  
Insight Into

AbstractIn solution-driven BID (sol-BID) a challenge is to identify suited applications that will benefit from the solutions principles found in nature. A well-known example of sol-BID is the self-cleaning lotus plant, that has inspired lotus paint and other coating methods. However, sol-BID is often performed by biologists with insight into the biological strategy and organism and typically only little knowledge of technical applications and design methodology. Searching for applications is therefore a challenge to many. Sol-BID has many things in common with technical application search where new applications are sought for a specific production technology or another competence characterizing a company. Experiences from technical application search could therefore form a valuable input for how to perform sol-BID. The paper presents two case studies of application search and proposes a procedure to be used in solution driven BID.

scholarly journals Spatial Distribution of Contextual Interactions in Primary Visual Cortex and in Visual Perception

2000 ◽  
Vol 84 (4) ◽  
pp. 2048-2062 ◽  
Author(s):  
Mitesh K. Kapadia ◽  
Gerald Westheimer ◽  
Charles D. Gilbert
Keyword(s):  
Spatial Distribution ◽  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Cortical Neurons ◽  
Receptive Fields ◽  
Human Perception ◽  
Spatial Arrangement ◽  
Orthogonal Axis ◽  
V1 Neurons ◽  
Contextual Interactions

To examine the role of primary visual cortex in visuospatial integration, we studied the spatial arrangement of contextual interactions in the response properties of neurons in primary visual cortex of alert monkeys and in human perception. We found a spatial segregation of opposing contextual interactions. At the level of cortical neurons, excitatory interactions were located along the ends of receptive fields, while inhibitory interactions were strongest along the orthogonal axis. Parallel psychophysical studies in human observers showed opposing contextual interactions surrounding a target line with a similar spatial distribution. The results suggest that V1 neurons can participate in multiple perceptual processes via spatially segregated and functionally distinct components of their receptive fields.

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