Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session B47: Focus Session: Physics of Behavior II |
Hide Abstracts |
Sponsoring Units: DBIO Chair: Joshua Shaevitz, Princeton University Room: 217B |
Monday, March 2, 2015 11:15AM - 11:27AM |
B47.00001: A computational investigation of the role of behavioral heterogeneities on cell cluster motion Katherine Copenhagen, Nir Gov, Ajay Gopinathan Collective motion of cells is a common occurence in many biological systems, including tissue develope- ment and repair, and tumor formation. Recent experiments have shown that malignant B and T lymphocytes form clusters in a chemical gradient of CCL19 which display three different phases: translational, rotational, and random. Could these phases be due to interactions between cells as well as chemotaxis of individuals? If so what types of local interactions can lead to the three phases seen in experiment? We model cell clusters with a continuous two dimensional agent based model. To form a single cell cluster which displays all three of the phases described above, cells interact with a Vicsek alignment interaction, a Lennard-Jones collision- avoidance and cohesiveness interaction, and a long range spring interaction to prevent fracture. By changing the behaviors of individual cells depending on the number of cells they are contacting, we are able to create clusters that occupy these phases with varying likelihood. Our results show that heterogeneous behaviors of individuals based on local environment can lead to novel phases seen in experiments. [Preview Abstract] |
(Author Not Attending)
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B47.00002: Optimal Intermittent Reorientation in Insect Navigation Orit Peleg, Lakshminarayanan Mahadevan The process of navigation is often accompanied by several cognitive demanding activities, such as motor control, locomotion planning, and multi-sensory acquisition and integration. Organisms with limited cognitive resources must therefore multitask and develop optimal schemes to dynamically allocate resources to the different tasks. An extreme example of task alternations during navigation is the hallmark of ball rolling dung beetles. The beetles need to roll their dung-ball along a straight path away from the dung pile where intense competition occurs [1]. Before initiating a roll, dung beetles climb on top of the ball and rotate about their vertical axis. This action serves as an orientation mechanism that allows them to set an initial bearing, and to regain this bearing if they experience an unintentional disturbance along the way [2]. We developed a model inspired by the beetle's navigational scheme, where an agent performs a random walk intermittent by reorientation events, in which its heading direction is corrected. We show that the resultant paths are a characteristic of correlated diffusion in short time scale, and biased diffusion in the long time scale [3]. We identify optimal alternation schemes and characterize their robustness upon introducing noisy sensory acquisition and rough environmental conditions.\\[4pt] [1] Warrant, E., {\&} Dacke, M. (2011)~\textit{Annual Review of Entomology}, 56(1), 239--254. \\[0pt] [2] Baird, E., Byrne, M. J., Smolka, J., Warrant, E. J., {\&} Dacke, M. (2012)~\textit{Plos One}, 7(1), e30211.\\[0pt] [3] Codling, E. A., Plank, M. J., {\&} Benhamou, S. (2008)~\textit{Journal of the Royal Society Interface}, 5(25), 813--834. [Preview Abstract] |
Monday, March 2, 2015 11:39AM - 11:51AM |
B47.00003: Self-righting behavior of cockroaches Chen Li, Toni Wohrl, Han Lam, Robert Full Small insects must be able to right themselves from an upside-down orientation to survive. Previous studies described diverse self-righting strategies in insects. Here, we compare the self-righting behaviors in three cockroach species on a flat, rigid ground to begin to reveal what governs the choice of dominant behaviors. All species self-righted successfully (75 $+$/- 11 {\%} probability) and quickly (as low as 140 ms and typically within 2 s). The smallest winged American cockroach, which has the most elongate, least flattened body, and longest legs, primarily pushed legs against the ground to roll its body to the side to self-right (relative frequency $=$ 93{\%}). The largest wingless Madagascar hissing cockroach with the shortest legs primarily (84{\%}) hyperextended body to roll to the side and then rubbed its legs on the ground to self-right. The intermediate winged discoid cockroach, which has the least elongate, most flattened body, more often (57{\%}) abducted wings and flexed body to raise center of mass and reduce ground contact and rotated about the wing edges to self-right. We hypothesize that, given morphological and physiological constraints, the gravitational potential energy landscape resulting from the animals' body/appendage-ground interaction governs their dominant behaviors. Our study provides inspiration for robotics, as many current terrestrial robots have rigid, cuboidal bodies which hinder self-righting. [Preview Abstract] |
Monday, March 2, 2015 11:51AM - 12:03PM |
B47.00004: Tiger beetle's pursuit of prey depends on distance Robert Noest, Jane Wang Tiger beetles are fast predators capable of chasing prey under closed-loop visual guidance. We investigated their control system using high-speed digital recordings of beetles chasing a moving prey dummy in a laboratory arena. Analysis reveals that the beetle uses a proportional control law in which the angular position of the prey relative to the beetle's body axis drives the beetle's angular velocity with a delay of about 28 ms. The system gain is shown to depend on the beetle-prey distance in a pattern indicating three hunting phases over the observed distance domain. We show that to explain this behavior the tiger beetle must be capable of visually determining the distance to its target and using that to adapt the gain in its proportional control law. We will end with a discussion on the possible methods for distance detection by the tiger beetle and focus on two of them. Motion parallax, using the natural head sway induced by the walking gait of the tiger beetle, is shown to have insufficient distance range. However elevation in the field of vision, using the angle with respect to the horizon at which a target is observed, has a much larger distance range and is a prime candidate for the mechanism of visual distance detection in the tiger beetle. [Preview Abstract] |
Monday, March 2, 2015 12:03PM - 12:15PM |
B47.00005: Hierarchy and predictability in spontaneous behavior Gordon Berman, William Bialek, Joshua Shaevitz Animals perform a complex array of behaviors, from changes in body posture to vocalizations to other dynamic outputs. Far from being a disordered collection of actions, however, there is thought to be an intrinsic structure to the set of behaviors and their temporal organization. This structure has often been hypothesized to be hierarchical, with certain behaviors grouped together into modules that interact with other modules at time scales that are long with respect to that of an individual behavior. There have been few measurements, however, showing that a particular animal's behavioral repertoire is organized hierarchically. This has largely resulted from an inability to measure the entirety of an animal's behavioral repertoire or even to definite precisely what a ``behavior'' is. In this talk, I will apply our novel method for mapping the behavioral space of animals to videos of freely-behaving fruit flies (\emph{D. melanogaster}), showing that the organisms' behavioral repertoire consists of a hierarchically-organized set of stereotyped behaviors. This hierarchical patterning results in the emergence of long time scales of memory in the system, providing insight into the mechanisms of behavioral control and patterning. [Preview Abstract] |
Monday, March 2, 2015 12:15PM - 12:27PM |
B47.00006: Environmental statistics and optimal regulation David Sivak, Matt Thomson The precision with which an organism can detect its environment, and the timescale for and statistics of environmental change, will affect the suitability of different strategies for regulating protein levels in response to environmental inputs. We propose a general framework---here applied to the enzymatic regulation of metabolism in response to changing nutrient concentrations---to predict the optimal regulatory strategy given the statistics of fluctuations in the environment and measurement apparatus, and the costs associated with enzyme production. We find: (i) relative convexity of enzyme expression cost and benefit influences the fitness of thresholding or graded responses; (ii) intermediate levels of measurement uncertainty call for a sophisticated Bayesian decision rule; and (iii) in dynamic contexts, intermediate levels of uncertainty call for retaining memory of the past. Statistical properties of the environment, such as variability and correlation times, set optimal biochemical parameters, such as thresholds and decay rates in signaling pathways. Our framework provides a theoretical basis for interpreting molecular signal processing algorithms and a classification scheme that organizes known regulatory strategies and may help conceptualize heretofore unknown ones. [Preview Abstract] |
Monday, March 2, 2015 12:27PM - 12:39PM |
B47.00007: Quantification of Behavior During \textit{Drosophila} Courtship Ugne Klibaite, Gordon Berman, Jessica Cande, David Stern, Joshua Shaevitz Fruit flies display varying and species-specific behavioral repertoires, especially during highly stereotyped activities such as courtship. Interspecies differences in specific behaviors may arise from physical differences, e.g. a different type or speed of appendage motion, or higher-order changes such as differences in the frequencies of particular actions. One example is the use of wing-rowing by \textit{D. santomea }males that is rarely, but sometimes, seen during \textit{D. yakuba }courtship. We wish to study the complex interaction of two individuals during courtship. We extend our group's previous work on mapping the postural dynamics of individual flies to analyze the simultaneous mapping of male and female behavior for hundreds of hours of courtship video data. Using this algorithm, we compare courtship behavior of dozens of targeted introgressions between \textit{D. yakuba }and \textit{D. santomea} to probe for differences in courtship and to determine which regions of the genome are responsible for this diversity. [Preview Abstract] |
Monday, March 2, 2015 12:39PM - 12:51PM |
B47.00008: Intrinsic fluctuations and driven response of insect swarms Rui Ni, James G. Puckett, Eric R. Dufresne, Nicholas T. Ouellette Much of our understanding of collective behaviour in social animals comes from passive observations of animal groups. To understand the group dynamics fully, however, we must also characterize the response of animal aggregations to disturbances. Using three-dimensional particle tracking, we study both the intrinsic fluctuations of laboratory swarms of the non-biting midge Chironomus riparius and the response of the swarms to controlled external perturbations: the amplitude-modulated sound of male midge wingbeats. Although these perturbations have an insignificant effect on the behavior of individuals, we find that they can have a strong impact on the collective movement. Intriguingly, the response of the swarm is similar reminiscent to of that of a passive equilibrium system to an external driving force, with microscopic fluctuations underlying combining to produce a macroscopic linear response over a wide range of driving frequencies. [Preview Abstract] |
Monday, March 2, 2015 12:51PM - 1:03PM |
B47.00009: Measuring Whole-Brain Neural Dynamics and Behavior of Freely-Moving \textit{C. elegans} Frederick Shipley, Jeffrey Nguyen, George Plummer, Joshua Shaevitz, Andrew Leifer Bridging the gap between an organism's neural dynamics and its ultimate behavior is the fundamental goal of neuroscience. Previously, to probe neural dynamics, we have been limited to measuring from a limited number of neurons, whether by electrode or optogenetic measurements. Here we present an instrument to simultaneously monitor neural activity from every neuron in a freely moving \textit{Caenorhabditis elegans}' head, while recording behavior at the same time. Previously, whole-brain imaging has been demonstrated in \textit{C. elegans}, but only in restrained and anesthetized animals (1). For studying neural coding of behavior it is crucial to study neural activity in freely behaving animals. Neural activity is recorded optically from cells expressing a calcium indicator, GCaMP6. Real time computer vision tracks the worm's position in x-y, while a piezo stage sweeps through the brain in z, yielding five brain-volumes per second. Behavior is recorded under infrared, dark-field imaging. This tool will allow us to directly correlate neural activity with behavior and we will present progress toward this goal. \\[4pt] [1] Robert Prevedel et al., ``Simultaneous Whole-Animal 3D Imaging of Neuronal Activity Using Light-Field Microscopy,'' \textit{Nature Methods} 11, no.7 (July 2014): 727-30 [Preview Abstract] |
Monday, March 2, 2015 1:03PM - 1:15PM |
B47.00010: Modulation of orthogonal body waves enables high maneuverability in sidewinding locomotion Henry Astley, Chaohui Gong, Matt Travers, Miguel Serrano, Patricio Vela, Howie Choset, Joseph Mendelson III, David Hu, Daniel Goldman To simplify control of high degree of freedom bodies, organisms may target a set of simple shape changes (a ``template''). Recent work has revealed that the locomotion of sidewinder rattlesnakes can be described by a combination of horizontal and vertical body waves with a phase difference of $\pm$$\pi$/2, representing a possible control template. These animals display high maneuverability which we hypothesize emerges from their ability to independently modulate these waves. Snakes used two distinct turning methods which we term differential turning ($24^\circ$ turn per cycle) and reversal turning ($80^\circ$). Kinematic data suggested that during differential turning the animals imposed an amplitude modulation in the horizontal wave while in reversal turning they shifted the phase of the vertical wave by $\pi$. We tested these mechanisms in the robot, generating differential and reversal turning. Further manipulations of the two-wave system revealed a third turning mode, ``frequency turning,'' not observed in biological snakes which allowed the robot to execute large ($127^\circ$) in-place turns. The two-wave system enables unprecedented maneuverability of high degree-of-freedom systems, revealing a practical benefits of the search for control templates. [Preview Abstract] |
Monday, March 2, 2015 1:15PM - 1:27PM |
B47.00011: Building spatially-structured biofilms with single-cell control using laser trapping Christopher Rodesney, Jaime Hutchison, Karishma Kaushik, Henry Le, Daniel Hurwitz, Yasuhiko Irie, Vernita Gordon Biofilms are sessile communities of microbes adhered to each other and to an interface. Biofilm infections are notoriously difficult to eradicate, and this arises in part from phenotypic changes due to the spatial structure of the biofilm. Spatial structure controls the microenvironment and intercellular associations, which in turn controls gene expression, virulence, and antibiotic resistance. There are few tools available for elucidating the role of spatial structure in biofilms. We present a method for controlling the positions of bacteria on a surface using optical trapping without impinging cell viability. Initial positions propagate into the developing biofilm, creating spatial structure. The native growth, motility, and surface adhesion of positioned cells are preserved, as shown for model organisms \textit{Pseudomonas aeruginosa} and \textit{Staphylococcus aureus}. We demonstrate statistically-significant effects of spatial structure on the growth of monoculture \textit{P. aeruginosa} biofilms and for co-culture biofilms of \textit{P. aeruginosa} and \textit{S. aureus}. Because the laser trap we use is very basic and the other equipment required is inexpensive and standard, we believe that our technique will be a widely-usable tool for biological and physical collaborators at many types of institutions. [Preview Abstract] |
Monday, March 2, 2015 1:27PM - 1:39PM |
B47.00012: Legless locomotion in lattices Perrin Schiebel, Jin Dai, Chaohui Gong, Miguel M. Serrano, Joseph R. Mendelson III, Howie Choset, Daniel I. Goldman By propagating waves from head to tail, limbless organisms like snakes can traverse terrain composed of rocks, foliage, soil and sand. Previous research elucidated how rigid obstacles influence snake locomotion by studying a model terrain--symmetric lattices of pegs placed in hard ground. We want to understand how different substrate-body interaction modes affect performance in desert-adapted snakes during transit of substrates composed of both rigid obstacles and granular media (GM). We tested \textit{Chionactis occipitalis}, the Mojave shovel-nosed snake, in two laboratory treatments: lattices of $0.64$cm diameter obstacles arrayed on both a hard, slick substrate and in a GM of $\approx 0.3$mm diameter glass particles. For all lattice spacings, $d$, speed through the hard ground lattices was less than that in GM lattices. However, maximal undulation efficiencies $\eta_u$ (number of body lengths advanced per undulation cycle) in both treatments were comparable when $d$ was intermediate. For other $d$, $\eta_u$ was lower than this maximum in hard ground lattices, while on GM, $\eta_u$ was insensitive to $d$. To systematically explore such locomotion, we tested a physical robot model of the snake; performance depended sensitively on base substrate, $d$ and body wave parameters. [Preview Abstract] |
Monday, March 2, 2015 1:39PM - 1:51PM |
B47.00013: Human pair walking behavior: evaluation of cooperation strategies Ulrich Dobramysl, Katarina Bodova, Richard Kollar, Radek Erban Human walkers are notoriously poor at keeping a direction without external cues: Experimental work by Souman {\it et al.} with blindfolded subjects told to walk in a straight line revealed intriguing circular and spiraling trajectories, which can be approximated by a stochastic process. In this work, motivated by pair walking experiments by Miglierini {\it et al.}, we introduce an analysis of various strategies employed by a pair of blindfolded walkers, who are communicating via auditory cues, to maximize their efficiency at walking straight. To this end, we characterize pairs of strategies such as free walking, side-by-side walking and unconditional following from data generated by robot pair walking experiments (using computer vision techniques) and numerical simulations. We extract the mean exit distances of walker pairs from a corridor with finite width to construct phase portraits of the walking performance. We find intriguing cooperative effects leading to non-trivial enhancements of the efficiency at walking straight. [Preview Abstract] |
Monday, March 2, 2015 1:51PM - 2:03PM |
B47.00014: Pili-mediated Interactions between Neisseria Gonorrhoeae Bacteria are the Driving Mechanism of Microcolony Merging Wolfram Poenisch, Christoph Weber, Khaled Alzurqa, Hadi Nasrollahi, Nicolas Biais, Vasily Zaburdaev During the early infection with Neisseria gonorrhoeae the bacteria form microcolonies consisting of a few hundreds to a few thousands of cells. The formation of colonies is mediated by type IV pili, thin and long filaments that are also involved in the motion of single cells over a substrate. A related process causes attractive cell-cell-interactions. While the motion of single cells has been extensively studied during the past years, the physical principles driving the growth of these colonies are poorly understood. One key mechanism of colony growth is coalescence of smaller colonies. Therefore we experimentally examine the process of merging of two Neisseria gonorrhoeae colonies. We develop a theoretical microscopic model of single cells interacting solely by their pili. The experimental data and the results obtained from our model are in excellent quantitative agreement. We observe a fast initial approach of the two merging colonies within a few minutes, that is followed by a slow relaxation of the colony shape with a characteristic time of several hours. These findings suggest that pili-mediated interactions are the primary driving mechanism of the microcolony merging process. [Preview Abstract] |
Monday, March 2, 2015 2:03PM - 2:15PM |
B47.00015: The growth and form of plant shoots Raghunath Chelakkot, L. Mahadevan Growing plant stems and shoots exhibit a variety of shapes that embody growth in response to various stimuli. We provide a quantitative biophysical theory for these shapes by accounting for the inherent observed passive and active effects: (i) the passive elastic deflection of the shoot due to its own weight, and (ii) the active controllable growth response of the shoot in response to its orientation relative to gravity, and (iii) proprioception, the shoot's growth response to its own observable shape, which is itself determined by its elasticity and weight. A morphospace diagram in terms of two dimensionless parameters representing a scaled local active gravitropic sensitivity, and a scaled passive elastic sag shows how a variety of observed transient and steady morphologies with effective positive, negative and even oscillatory gravitropic behaviors arise in a sentient growing filament naturally, without the need for ad-hoc complex spatio-temporal control strategies. [Preview Abstract] |
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