scholarly journals Chemotaxis overrides Barotaxis during Directional Decision-Making in Dictyostelium discoideum

2020 ◽  
Author(s):  
Yuri Belotti ◽  
David McGloin ◽  
Cornelis J. Weijer
Keyword(s):  
Decision Making ◽  
Dendritic Cells ◽  
Hydraulic Resistance ◽  
Dictyostelium Discoideum ◽  
Average Velocity ◽  
Leading Edge ◽  
Decision Threshold ◽  
Chemical Gradient ◽  
Critical Tension ◽  
Micro Channels

AbstractNeutrophils and dendritic cells have, besides their well characterised chemotactic movement responses, been shown to be able to detect and respond to local differences in hydraulic resistance (barotaxis). Furthermore, for neutrophils, it has been suggested that barotaxis overrides chemotaxis. Here, we investigate whether Dictyostelium cells also respond to hydraulic resistance or primarily to chemical gradients using an asymmetric bifurcating micro-channel. This channel design allows us to decouple hydraulic and chemical stimuli, by providing a choice between moving up a chemical gradient or down a chemical gradient into a channel with 100 times lower hydraulic resistance. Under these conditions chemotaxis always overrides barotaxis. Cells confronted by a microchannel bifurcation are observed to often partially split their leading edge and to start moving into both channels. Cells in steeper cAMP gradients, that move faster, split more readily. The decision to retract the pseudopod moving away from the cAMP source is made when the average velocity of the pseudopod moving up the cAMP gradient is 20% higher than the average velocity of the pseudopod moving down the gradient. Surprisingly, this decision threshold is independent of the steepness of the cAMP gradient and speed of movement. It indicates that a critical force imbalance threshold underlies the repolarisation decision.Significance StatementWe investigate the directional ‘decision-making’ of Dictyostelium discoideum cells migrating within engineered micro-channels harbouring asymmetric bifurcations. Unlike neutrophils and immature dendritic cells, Dictyostelium cells strongly prioritise chemical over barotactic guidance cues. Cells in steeper cAMP gradients migrate at higher speeds, split their leading edges more readily when confronted with a bifurcation in the channel. The decision to retract a pseudopod pointing in an unfavourable direction occurs when a critical tension gradient between two competing pseudopods is surpassed. These experiments show that although barotaxis is not a major guidance cue, cellular mechanics plays a major role in leading edge dynamics, including front splitting and polarisation and retraction.

scholarly journals Same model, different conclusions: An identifiability issue in the linear ballistic accumulator model of decision-making

2020 ◽  
Author(s):  
Nathan J. Evans
Keyword(s):  
Decision Making ◽  
Diffusion Model ◽  
Large Scale ◽  
Drift Rate ◽  
Decision Time ◽  
Measurement Properties ◽  
Decision Threshold ◽  
Experimental Conditions ◽  
Model Application ◽  
Linear Ballistic Accumulator

Evidence accumulation models (EAMs) – the dominant modelling framework for speeded decision-making – have become an important tool for model application. Model application involves using specific model to estimate parameter values that relate to different components of the cognitive process, and how these values differ over experimental conditions and/or between groups of participants. In this context, researchers are often agnostic to the specific theoretical assumptions made by different EAM variants, and simply desire a model that will provide them with an accurate measurement of the parameters that they are interested in. However, recent research has suggested that the two most commonly applied EAMs – the diffusion model and the linear ballistic accumulator (LBA) – come to fundamentally different conclusions when applied to the same empirical data. The current study provides an in-depth assessment of the measurement properties of the two models, as well as the mapping between, using two large scale simulation studies and a reanalysis of Evans (2020a). Importantly, the findings indicate that there is a major identifiability issue within the standard LBA, where differences in decision threshold between conditions are practically unidentifiable, which appears to be caused by a tradeoff between the threshold parameter and the overall drift rate across the different accumulators. While this issue can be remedied by placing some constraint on the overall drift rate across the different accumulators – such as constraining the average drift rate or the drift rate of one accumulator to have the same value in each condition – these constraints can qualitatively change the conclusions of the LBA regarding other constructs, such as non-decision time. Furthermore, all LBA variants considered in the current study still provide qualitatively different conclusions to the diffusion model. Importantly, the current findings suggest that researchers should not use the unconstrained version of the LBA for model application, and bring into question the conclusions of previous studies using the unconstrained LBA.

scholarly journals Directed migration: Cells navigate by extracellular vesicles

2018 ◽  
Vol 217 (8) ◽  
pp. 2613-2614 ◽  
Author(s):  
Bong Hwan Sung ◽  
Alissa M. Weaver
Keyword(s):  
Cell Motility ◽  
Dictyostelium Discoideum ◽  
Extracellular Vesicles ◽  
Cancer Metastasis ◽  
Chemical Gradient ◽  
Directed Migration ◽  
Cell Biol

Directional cell motility toward a chemical gradient, chemotaxis, is critical during inflammation, embryogenesis, and cancer metastasis. In this issue, Kriebel et al. (2018. J. Cell Biol. https://doi.org/10.1083/jcb.201710170) demonstrate that the key cAMP chemoattractant for Dictyostelium discoideum amoebas is synthesized within and released from extracellular vesicles to promote chemotaxis.

scholarly journals Analysis of barotactic and chemotactic guidance cues on directional decision-making ofDictyostelium discoideumcells in confined environments

2020 ◽  
Vol 117 (41) ◽  
pp. 25553-25559 ◽  
Author(s):  
Yuri Belotti ◽  
David McGloin ◽  
Cornelis J. Weijer
Keyword(s):  
Decision Making ◽  
Single Cells ◽  
Model Organism ◽  
Leading Edge ◽  
Decision Making Process ◽  
Chip Design ◽  
Cortical Tension ◽  
Channel Analysis ◽  
Chemical Stimuli ◽  
Total Velocity

Neutrophils and dendritic cells when migrating in confined environments have been shown to actuate a directional choice toward paths of least hydraulic resistance (barotaxis), in some cases overriding chemotactic responses. Here, we investigate whether this barotactic response is conserved in the more primitive model organismDictyostelium discoideumusing a microfluidic chip design. This design allowed us to monitor the behavior of single cells via live imaging when confronted with bifurcating microchannels, presenting different combinations of hydraulic and chemical stimuli. Under the conditions employed we find no evidence in support of a barotactic response; the cells base their directional choices on the chemotactic cues. When the cells are confronted by a microchannel bifurcation, they often split their leading edge and start moving into both channels, before a decision is made to move into one and retract from the other channel. Analysis of this decision-making process has shown that cells in steeper nonhydrolyzable adenosine- 3', 5'- cyclic monophosphorothioate, Sp- isomer (cAMPS) gradients move faster and split more readily. Furthermore, there exists a highly significant strong correlation between the velocity of the pseudopod moving up the cAMPS gradient to the total velocity of the pseudopods moving up and down the gradient over a large range of velocities. This suggests a role for a critical cortical tension gradient in the directional decision-making process.

Contractor and supplier management: mitigating risk by better decision making

2012 ◽  
Vol 52 (2) ◽  
pp. 642
Author(s):  
Dag Yemenu ◽  
Richard Cerenzio
Keyword(s):  
Decision Making ◽  
Oil And Gas ◽  
Safety Management ◽  
Safety Data ◽  
Health And Safety ◽  
Leading Edge ◽  
Third Party ◽  
Driving Safety ◽  
Comprehensive Management ◽  
And Performance

Global industry trends show increased outsourcing of non-core business activities (i.e. construction, maintenance, engineering, etc.) to third-party contractors. Data from several industries show that contractors face 1.5–3 times higher incident rates than in-house employees. This extended abstract covers leading-edge approaches for managing contractor risk, presently implemented by organisations in the oil and gas, mining and manufacturing industries. Using a database of more than 35,000 contracting companies and 220 owner/operator companies, this extended abstract accumulates more than six years of extensive health and safety data to show trends associated with health and safety management and performance improvement. Using statistical analysis methods, actionable leading indicators and insightful trends are discussed. Best practices of contractor management and decision-making tools based on a comprehensive management-system approach to contractor-risk management are also examined. Discussed is a practical model to address the following key elements: Gathering, reviewing and verifying contractor information as part of the due-diligence process. Analysing leading and lagging performance indicators. Driving safety through feedback, benchmarking, and continual improvement.

Decision making under uncertainty and mood induction: further evidence for liberal acceptance in schizophrenia

2009 ◽  
Vol 39 (11) ◽  
pp. 1821-1829 ◽  
Author(s):  
S. Moritz ◽  
R. Veckenstedt ◽  
S. Randjbar ◽  
B. Hottenrott ◽  
T. S. Woodward ◽  
...  
Keyword(s):  
Decision Making ◽  
Healthy Subjects ◽  
Mood Induction ◽  
Cognitive Biases ◽  
Random Order ◽  
Vital Role ◽  
Decision Making Under Uncertainty ◽  
Decision Threshold ◽  
Healthy Controls ◽  
Second Best

BackgroundCognitive biases, especially jumping to conclusions (JTC), are ascribed a vital role in the pathogenesis of schizophrenia. This study set out to explore motivational factors for JTC using a newly developed paradigm.MethodTwenty-seven schizophrenia patients and 32 healthy controls were shown 15 classical paintings, divided into three blocks. Four alternative titles (one correct and three lure titles) had to be appraised according to plausibility (0–10). Optionally, participants could decide for one option and reject one or more alternatives. In random order across blocks, anxiety-evoking music, happy music or no music was played in the background.ResultsPatients with schizophrenia, particularly those with delusions, made more decisions than healthy subjects. In line with the liberal acceptance (LA) account of schizophrenia, the decision threshold was significantly lowered in patients relative to controls. Patients were also more prone than healthy controls to making a decision when the distance between the first and second best alternative was close. Furthermore, implausible alternatives were judged as significantly more plausible by patients. Anxiety-evoking music resulted in more decisions in currently deluded patients relative to non-deluded patients and healthy controls.ConclusionsThe results confirm predictions derived from the LA account and assert that schizophrenia patients decide hastily under conditions of continued uncertainty. The fact that mood induction did not exert an overall effect could be due to the explicit nature of the manipulation, which might have evoked strategies to counteract their influence.

scholarly journals Foraging as an evidence accumulation process

2018 ◽  
Author(s):  
Jacob D. Davidson ◽  
Ahmed El Hady
Keyword(s):  
Decision Making ◽  
Diffusion Processes ◽  
Optimal Strategies ◽  
Theoretical Work ◽  
Decision Threshold ◽  
Residence Times ◽  
Marginal Value ◽  
Evidence Accumulation ◽  
Current Resource ◽  
Noisy Measurements

AbstractA canonical foraging task is the patch-leaving problem, in which a forager must decide to leave a current resource in search for another. Theoretical work has derived optimal strategies for when to leave a patch, and experiments have tested for conditions where animals do or do not follow an optimal strategy. Nevertheless, models of patch-leaving decisions do not consider the imperfect and noisy sampling process through which an animal gathers information, and how this process is constrained by neurobiological mechanisms. In this theoretical study, we formulate an evidence accumulation model of patch-leaving decisions where the animal averages over noisy measurements to estimate the state of the current patch and the overall environment. Evidence accumulation models belong to the class of drift diffusion processes and have been used to model decision making in different contexts especially in cognitive and systems neuroscience. We solve the model for conditions where foraging decisions are optimal and equivalent to the marginal value theorem, and perform simulations to analyze deviations from optimal when these conditions are not met. By adjusting the drift rate and decision threshold, the model can represent different “strategies”, for example an increment-decrement or counting strategy. These strategies yield identical decisions in the limiting case but differ in how patch residence times adapt when the foraging environment is uncertain. To account for sub-optimal decisions, we introduce an energy-dependent utility function that predicts longer than optimal patch residence times when food is plentiful. Our model provides a quantitative connection between ecological models of foraging behavior and evidence accumulation models of decision making. Moreover, it provides a theoretical framework for potential experiments which seek to identify neural circuits underlying patch leaving decisions.

scholarly journals Inhibition of Pre–Supplementary Motor Area by Continuous Theta Burst Stimulation Leads to More Cautious Decision-making and More Efficient Sensory Evidence Integration

2017 ◽  
Vol 29 (8) ◽  
pp. 1433-1444 ◽  
Author(s):  
Tuğçe Tosun ◽  
Dilara Berkay ◽  
Alexander T. Sack ◽  
Yusuf Ö. Çakmak ◽  
Fuat Balcı
Keyword(s):  
Decision Making ◽  
Decision Threshold ◽  
Theta Burst Stimulation ◽  
Burst Stimulation ◽  
Sensory Evidence ◽  
Speed Accuracy ◽  
Theta Burst ◽  
Continuous Theta Burst Stimulation ◽  
Accuracy Tradeoff ◽  
Evidence Integration

Decisions are made based on the integration of available evidence. The noise in evidence accumulation leads to a particular speed–accuracy tradeoff in decision-making, which can be modulated and optimized by adaptive decision threshold setting. Given the effect of pre-SMA activity on striatal excitability, we hypothesized that the inhibition of pre-SMA would lead to higher decision thresholds and an increased accuracy bias. We used offline continuous theta burst stimulation to assess the effect of transient inhibition of the right pre-SMA on the decision processes in a free-response two-alternative forced-choice task within the drift diffusion model framework. Participants became more cautious and set higher decision thresholds following right pre-SMA inhibition compared with inhibition of the control site (vertex). Increased decision thresholds were accompanied by an accuracy bias with no effects on post-error choice behavior. Participants also exhibited higher drift rates as a result of pre-SMA inhibition compared with the vertex inhibition. These results, in line with the striatal theory of speed–accuracy tradeoff, provide evidence for the functional role of pre-SMA activity in decision threshold modulation. Our results also suggest that pre-SMA might be a part of the brain network associated with the sensory evidence integration.

scholarly journals Evidence or Confidence: What Really Accumulates During a Decision?

2021 ◽  
Author(s):  
Douglas G. Lee ◽  
Giovanni Pezzulo
Keyword(s):  
Decision Making ◽  
Empirical Evidence ◽  
Alternative Hypothesis ◽  
Decision Threshold ◽  
Drift Diffusion Model ◽  
Drift Diffusion ◽  
Evidence Accumulation ◽  
Confidence Assessment ◽  
Standard Models ◽  
Post Hoc

Assessing one's confidence in one's choices is of paramount importance to making adaptive decisions, and it is thus no surprise that humans excel in this ability. However, standard models of decision-making, such as the drift-diffusion model (DDM), treat confidence assessment as a post-hoc or parallel process that does not directly influence the choice -- the latter depends only on accumulated evidence. Here, we pursue the alternative hypothesis that what is accumulated during a decision is confidence (that the to-be selected option is the best) rather than raw evidence. Accumulating confidence has the appealing consequence that the decision threshold corresponds to a desired level of confidence for the choice, and that confidence improvements can be traded off against the resources required to secure them. We show that most previous findings on perceptual and value-based decisions traditionally interpreted from an evidence-accumulation perspective can be explained more parsimoniously from our novel confidence-driven perspective. Furthermore, we show that our novel confidence-driven DDM (cDDM) naturally generalizes to any number of decisions -- which is notoriously extemporaneous using traditional DDM or related models. Finally, we discuss future empirical evidence that could be useful in adjudicating between these alternatives.

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