ORCID Profile
0000-0001-8556-4558
Current Organisations
University of Manchester
,
Max Planck Institute of Animal Behavior
,
University of Konstanz
,
Imperial College London
,
University of Oxford Balliol College
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Adaptive Agents and Intelligent Robotics | Zoology | Animal Behaviour | Simulation and Modelling
Expanding Knowledge in the Information and Computing Sciences | Expanding Knowledge in the Biological Sciences |
Publisher: American Society of Hematology
Date: 06-06-2013
DOI: 10.1182/BLOOD-2013-02-482570
Abstract: Rituximab causes a polarization of B cells, involving a reorganization of CD20, intercellular adhesion molecule 1, and moesin, and orientation of the microtubule organizing center. The polarization of B cells induced by rituximab augments its therapeutic role in triggering ADCC by effector NK cells.
Publisher: Springer Science and Business Media LLC
Date: 23-03-2011
DOI: 10.1038/NATURE09831
Publisher: Proceedings of the National Academy of Sciences
Date: 23-04-2021
Abstract: Human-designed infrastructures and networks relying on centralized or hierarchical control are susceptible to single-point catastrophic failure when disrupted. By contrast, most complex biological systems employ distributed control and can be more robust to perturbations. In field experiments with Eciton burchellii army ants, we show that scaffold structures, self-assembled by living ants, emerge in response to disrupted traffic on inclines, facilitating traffic flow and stemming losses of foragers and prey. Informed by our observations, we present a theoretical model based on proportional control and negative feedback, which may be relevant to many distributed systems in which group-level properties can be modified through in idual error sensing and correction. The mechanism is simple, and ants only require information about their in idual state.
Publisher: Springer Science and Business Media LLC
Date: 05-2008
DOI: 10.1007/S12064-008-0040-1
Abstract: Moving animal groups provide some of the most intriguing and difficult to characterise ex les of collective behaviour. We review some recent (and not so recent) empirical research on the motion of animal groups, including fish, locusts and homing pigeons. An important concept which unifies our understanding of these groups is that of transfer of directional information. In iduals which change their direction of travel in response to the direction taken by their near neighbours can quickly transfer information about the presence of a predatory threat or food source. We show that such information transfer is optimised when the density of in iduals in a group is close to that at which a phase transition occurs between random and ordered motion. Similarly, we show that even relatively small differences in information possessed by group members can lead to strong collective-level decisions for one of two options. By combining the use of self-propelled particle and social force models of collective motion with thinking about the evolution of flocking we aim to better understand how complexity arises within these groups.
Publisher: eLife Sciences Publications, Ltd
Date: 31-01-2017
DOI: 10.7554/ELIFE.19505
Abstract: For group-living animals traveling through heterogeneous landscapes, collective movement can be influenced by both habitat structure and social interactions. Yet research in collective behavior has largely neglected habitat influences on movement. Here we integrate simultaneous, high-resolution, tracking of wild baboons within a troop with a 3-dimensional reconstruction of their habitat to identify key drivers of baboon movement. A previously unexplored social influence – baboons’ preference for locations that other troop members have recently traversed – is the most important predictor of in idual movement decisions. Habitat is shown to influence movement over multiple spatial scales, from long-range attraction and repulsion from the troop’s sleeping site, to relatively local influences including road-following and a short-range avoidance of dense vegetation. Scaling to the collective level reveals a clear association between habitat features and the emergent structure of the group, highlighting the importance of habitat heterogeneity in shaping group coordination.
Publisher: The Royal Society
Date: 19-04-2017
Abstract: Researchers have long noted that in iduals occupy consistent spatial positions within animal groups. However, an in idual's position depends not only on its own behaviour, but also on the behaviour of others. Theoretical models of collective motion suggest that global patterns of spatial assortment can arise from in idual variation in local interaction rules. However, this prediction remains untested. Using high-resolution GPS tracking of members of a wild baboon troop, we identify consistent inter-in idual differences in within-group spatial positioning. We then apply an algorithm that identifies what number of conspecific group members best predicts the future location of each in idual (we call this the in idual's neighbourhood size ) while the troop is moving. We find clear variation in the most predictive neighbourhood size, and this variation relates to in iduals' propensity to be found near the centre of their group. Using simulations, we show that having different neighbourhood sizes is a simple candidate mechanism capable of linking variation in local in idual interaction rules—in this case how many conspecifics an in idual interacts with—to global patterns of spatial organization, consistent with the patterns we observe in wild primates and a range of other organisms.
Publisher: Proceedings of the National Academy of Sciences
Date: 07-04-2009
Abstract: Among the most striking aspects of the movement of many animal groups are their sudden coherent changes in direction. Recent observations of locusts and starlings have shown that this directional switching is an intrinsic property of their motion. Similar direction switches are seen in self-propelled particle and other models of group motion. Comprehending the factors that determine such switches is key to understanding the movement of these groups. Here, we adopt a coarse-grained approach to the study of directional switching in a self-propelled particle model assuming an underlying one-dimensional Fokker–Planck equation for the mean velocity of the particles. We continue with this assumption in analyzing experimental data on locusts and use a similar systematic Fokker–Planck equation coefficient estimation approach to extract the relevant information for the assumed Fokker–Planck equation underlying that experimental data. In the experiment itself the motion of groups of 5 to 100 locust nymphs was investigated in a homogeneous laboratory environment, helping us to establish the intrinsic dynamics of locust marching bands. We determine the mean time between direction switches as a function of group density for the experimental data and the self-propelled particle model. This systematic approach allows us to identify key differences between the experimental data and the model, revealing that in idual locusts appear to increase the randomness of their movements in response to a loss of alignment by the group. We give a quantitative description of how locusts use noise to maintain swarm alignment. We discuss further how properties of in idual animal behavior, inferred by using the Fokker–Planck equation coefficient estimation approach, can be implemented in the self-propelled particle model to replicate qualitatively the group level dynamics seen in the experimental data.
Publisher: The Royal Society
Date: 25-08-2010
Abstract: In order to move effectively in unpredictable or heterogeneous environments animals must make appropriate decisions in response to internal and external cues. Identifying the link between these components remains a challenge for movement ecology and is important in understanding the mechanisms driving both in idual and collective motion. One accessible way of examining how internal state influences an in idual's motion is to consider the nutritional state of an animal. Our experimental results reveal that nutritional state exerts a relatively minor influence on the motion of isolated in iduals, but large group-level differences emerge from diet affecting inter-in idual interactions. This supports the idea that mass movement in locusts may be driven by cannibalism. To estimate how these findings are likely to impact collective migration of locust hopper bands, we create an experimentally parametrized model of locust interactions and motion. Our model supports our hypothesis that nutrient-dependent social interactions can lead to the collective motion seen in our experiments and predicts a transition in the mean speed and the degree of coordination of bands with increasing insect density. Furthermore, increasing the interaction strength (representing greater protein deprivation) dramatically reduces the critical density at which this transition occurs, demonstrating that in iduals' nutritional state could have a major impact on large-scale migration.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 23-07-2013
DOI: 10.1126/SCISIGNAL.2003947
Abstract: The repositioning of inhibitory receptors on natural killer cells by an activating receptor is revealed by superresolution microscopy.
Publisher: American Society for Microbiology
Date: 15-03-2007
DOI: 10.1128/JVI.02415-06
Abstract: CD8 T cells exert their antiviral function through cytokines and lysis of infected cells. Because hepatocytes are susceptible to noncytolytic mechanisms of viral clearance, CD8 T-cell antiviral efficiency against hepatotropic viruses has been linked to their capacity to produce gamma interferon (IFN-γ) and tumor necrosis factor alpha (TNF-α). On the other hand, intrahepatic cytokine production triggers the recruitment of mononuclear cells, which sustain acute and chronic liver damage. Using virus-specific CD8 T cells and human hepatocytes, we analyzed the modulation of virus-specific CD8 T-cell function after recognition peptide-pulsed or virally infected hepatocytes. We observed that hepatocyte antigen presentation was generally inefficient, and the quantity of viral antigen strongly influenced CD8 T-cell antiviral function. High levels of hepatitis B virus production induced robust IFN-γ and TNF-α production in virus-specific CD8 T cells, while limiting amounts of viral antigen, both in hepatocyte-like cells and naturally infected human hepatocytes, preferentially stimulated CD8 T-cell degranulation. Our data document a mechanism where virus-specific CD8 T-cell function is influenced by the quantity of virus produced within hepatocytes.
Publisher: Wiley
Date: 08-08-2012
DOI: 10.1111/J.1461-0248.2012.01840.X
Abstract: During outbreaks, locust swarms can contain millions of insects travelling thousands of kilometers while devastating vegetation and crops. Such large-scale spatial organization is preceded locally by a dramatic density-dependent phenotypic transition in multiple traits. Behaviourally, low-density 'solitarious' in iduals avoid contact with one another above a critical local density, they undergo a rapid behavioural transition to the 'gregarious phase' whereby they exhibit mutual attraction. Although proximate causes of this phase polyphenism have been widely studied, the ultimate driving factors remain unclear. Using an in idual-based evolutionary model, we reveal that cannibalism, a striking feature of locust ecology, could lead to the evolution of density-dependent behavioural phase-change in juvenile locusts. We show that this behavioural strategy minimizes risk associated with cannibalistic interactions and may account for the empirically observed persistence of locust groups during outbreaks. Our results provide a parsimonious explanation for the evolution of behavioural plasticity in locusts.
Publisher: IOP Publishing
Date: 11-06-2013
DOI: 10.1088/1478-3975/10/4/046002
Abstract: When motile cells come into contact with one another their motion is often considerably altered. In a process termed contact inhibition of locomotion (CIL) cells reshape and redirect their movement as a result of cell-cell contact. Here we describe a mathematical model that demonstrates that CIL alone is sufficient to produce coherent, collective cell migration. Our model illustrates a possible mechanism behind collective cell migration that is observed, for ex le, in neural crest cells during development, and in metastasizing cancer cells. We analyse the effects of varying cell density and shape on the alignment patterns produced and the transition to coherent motion. Finally, we demonstrate that this process may have important functional consequences by enhancing the accuracy and robustness of the chemotactic response, and factors such as cell shape and cell density are more significant determinants of migration accuracy than the in idual capacity to detect environmental gradients.
Publisher: Wiley
Date: 10-10-2013
DOI: 10.1111/IMR.12107
Abstract: Natural killer (NK) cells discriminate between healthy and unhealthy target cells through a balance of activating and inhibitory signals at direct intercellular contacts called immune synapses. Rearrangements in the cellular cytoskeleton have long been known to be critical in assembly of immune synapses. Here, through bringing together the vast literature on this subject, the number of different ways in which the cytoskeleton is important becomes evident. The dynamics of filamentous actin are critical in (i) creating the nanometer-scale organization of NK cell receptors, (ii) establishing cellular polarity, (iii) coordinating immune receptor and integrin-mediated signaling, and (iv) directing secretion of lytic granules and cytokines. The microtubule network also is important in the delivery of lytic granules and vesicles containing cytokines to the immune synapse. Together, these data establish that the cytoskeleton acts as a central regulator of this complex and dynamic process - and an enormous amount of NK cell biology is controlled through the cytoskeleton.
Publisher: Elsevier BV
Date: 09-2018
Publisher: Public Library of Science (PLoS)
Date: 14-12-2010
Publisher: Proceedings of the National Academy of Sciences
Date: 21-06-2021
Abstract: Collective behavior provides a framework for understanding how the actions and properties of groups emerge from the way in iduals generate and share information. In humans, information flows were initially shaped by natural selection yet are increasingly structured by emerging communication technologies. Our larger, more complex social networks now transfer high-fidelity information over vast distances at low cost. The digital age and the rise of social media have accelerated changes to our social systems, with poorly understood functional consequences. This gap in our knowledge represents a principal challenge to scientific progress, democracy, and actions to address global crises. We argue that the study of collective behavior must rise to a “crisis discipline” just as medicine, conservation, and climate science have, with a focus on providing actionable insight to policymakers and regulators for the stewardship of social systems.
Publisher: American Physical Society (APS)
Date: 29-07-2010
Publisher: EMBO
Date: 17-07-2017
Publisher: Elsevier BV
Date: 05-2016
Publisher: Proceedings of the National Academy of Sciences
Date: 29-12-2009
Abstract: Locating the source of an advected chemical signal is a common challenge facing many living organisms. When the advecting medium is characterized by either high Reynolds number or high Peclet number, the task becomes highly nontrivial due to the generation of heterogeneous, dynamically changing filamental concentrations that do not decrease monotonically with distance to the source. Defining search strategies that are effective in these environments has important implications for the understanding of animal behavior and for the design of biologically inspired technology. Here we present a strategy that is able to solve this task without the higher intelligence required to assess spatial gradient direction, measure the diffusive properties of the flow field, or perform complex calculations. Instead, our method is based on the collective behavior of autonomous in iduals following simple social interaction rules which are modified according to the local conditions they are experiencing. Through these context-dependent interactions, the group is able to locate the source of a chemical signal and in doing so displays an awareness of the environment not present at the in idual level. This behavior illustrates an alternative pathway to the evolution of higher cognitive capacity via the emergent, group-level intelligence that can result from local interactions.
Publisher: Proceedings of the National Academy of Sciences
Date: 23-11-2015
Abstract: Complex systems, from ant colonies to stock markets, share a common property: sophisticated group-level structure emerges from simple in idual-level behaviors. Using simple interaction rules, Eciton army ants construct complex bridges from their own bodies to span forest-floor gaps. These living bridges are uniquely complex in both their dynamic properties and the number of animals involved and so are of considerable interest for understanding emergent structures in complex systems. In field experiments, we show that construction interacts with traffic rate and environmental geometry, causing bridges to lengthen, widen, and migrate. Bridges provide a shortcut for foraging ants, at the cost of sequestering workers. We show that bridge location represents a cost–benefit trade-off, with potential implications for human engineered self-assembling systems.
Publisher: American Society of Hematology
Date: 11-01-2007
DOI: 10.1182/BLOOD-2006-10-052977
Abstract: Natural killer (NK) cells directly lyse tumor or viral-infected cells but also an important role for NK cell cytotoxicity in regulating the extent of immune responses is emerging. Here, we show that autologous human macrophages activated NK cell proliferation and cytokine secretion, increased expression of activating receptors, and primed NK cell cytotoxicity against susceptible target cells. Ligation of NK cell 2B4, and not NKp30 (known to be important for DC-mediated NK cell activation), is critical for this macrophage-mediated NK cell activation. Reciprocally, however, NK cells regulated macrophage activity by directly killing macrophages stimulated by high doses of LPS. Cytolysis was triggered by NKG2D recognition of stress-inducible class I major histocompatibility complex (MHC)–like ligands on macrophages: high doses of LPS induced transcription and surface expression of ULBP1, ULBP2, and ULBP3 and surface expression of constitutively transcribed MICA. Thus, these data suggest a new function for NK cell cytotoxicity in eliminating overstimulated macrophages. Additionally, these interactions define, for the first time, 2 distinct activating NK cell synapses: lytic and nonlytic. Triggering NK cell proliferation and cytokine secretion, but not cytolysis, specifically associated with synaptic accumulation of macrophage F-actin and NK cell 2B4, while macrophages were killed when NK cell F-actin and macrophage ICAM-1 accumulated around a central cluster of NK cell NKG2D/DAP10.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 19-06-2015
Abstract: How do groups of animals, including humans, make decisions that affect the entire group? Evidence collected from schooling animals suggests that the process is somewhat democratic, with nearest neighbors and the majority shaping overall collective behavior. In animals with hierarchical social structures such as primates or wolves, however, such democracy may be complicated by dominance. Strandburg-Peshkin et al. monitored all the in iduals within a baboon troop continuously over the course of their daily activities. Even within this highly socially structured species, movement decisions emerged via a shared process. Thus, democracy may be an inherent trait of collective behavior. Science , this issue p. 1358
Publisher: eLife Sciences Publications, Ltd
Date: 19-07-2022
DOI: 10.7554/ELIFE.76344
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 02-2021
End Date: 01-2024
Amount: $596,886.00
Funder: Australian Research Council
View Funded Activity