Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session A65: Physics of Behavior IFocus
|
Hide Abstracts |
Sponsoring Units: DBIO Chair: Greg Stephens, Vrije Universiteit Room: BCEC 260 |
Monday, March 4, 2019 8:00AM - 8:36AM |
A65.00001: Reading the mind of the worm: Brain-wide neural dynamics predict behavior in C. elegans Invited Speaker: Monika Scholz We record calcium activity from the majority of head neurons in freely moving C. elegans to reveal where and how natural behavior is encoded in a compact brain. We find that a sparse subset of neurons distributed throughout the head encode locomotion. A linear combination of these neurons’ activity predicts the animal's velocity and body curvature and is sufficient to infer its posture. This sparse linear model outperforms single neuron or PCA models at predicting behavior. Among neurons important for the prediction are well-known locomotory neurons, such as AVA, as well as neurons not traditionally associated with locomotion. We compare neural activity of the same animal during unrestrained movement and during immobilization and find large differences between brain-wide neural dynamics during real and fictive locomotion. |
Monday, March 4, 2019 8:36AM - 8:48AM |
A65.00002: Root Circumnutation Facilitates Effective Subterranean Surface Exploration Erin N McCaskey, Kevin R Lehner, Isaiah Taylor, Yasemin Ozkan aydin, Enes Aydin, Philip Benfey, Daniel Goldman Circumnutation is the oscillatory movement first described by Darwin of a variety of plant organs including roots. A number of root traits have been suggested to improve tip penetration in environments where soil mechanical impedance is a limiting factor in growth, though little is known about the roles of circumnutation. After observing a root coiling phenotype on flat surfaces in non-circumnutating mutant rice roots, we hypothesized that root tip circumnutation facilitates effective root-surface exploration. To model a surface environment of a compact soil horizon with biopores we used plates with 2mm holes equally spaced at different densities. Mutant and wild-type (WT) rice were grown in a clear gel-based media and an automated high-throughput system acquired images to visualize the root growth. As hole density decreased mutants showed reduced success in finding a hole. WT roots had higher success indicating WT roots are more effective in flat surface exploration and less affected by sparse hole density, providing a plausible mechanism to buffer against environmental uncertainty inherent in soil exploration. We propose circumnutation provides a mechanism to break the intrinsic root coiling pattern seen in mutants, and that this movement consequently promotes root exploration. |
Monday, March 4, 2019 8:48AM - 9:00AM |
A65.00003: Worm blob dynamics under thermal stress Yasemin Ozkan aydin, Daniel Goldman, Saad Bhamla Aggregate formation and clustering are common behaviors observed from bacteria to humans, and can facilitate the survival of the collective [Allee, 1978]. Here we discuss aggregation behavior in aquatic worms and its potential biological function. We first show how aquatic worms can be induced to aggregate into ensembles of thousands of worms that knot together, forming an active viscoelastic ‘blob’. This worm blob can be modulated from an elastic solid-like state to a viscous liquid-like state by changing the surrounding temperature. To establish how this complex transition occurs, we measure both the dynamics of individual worms and the collective. In single worms, we find that activity of an individual worm increases with temperature and reaches a peak value (0.05 cm/s) around 32°C. Thus, in groups at lower temperature (10°C), individual worms are less active and entangle together, while at higher temperatures (35°C), individual worms are more active and disentangle. More specifically, the steady-state density of the cluster decreases from 75% to 33% as temperature increases from 15 to 35°C, respectively. Our results suggest that worm’s aggregates may serve as a robust survival strategy of the collective against environmental thermal stresses. |
Monday, March 4, 2019 9:00AM - 9:12AM |
A65.00004: Dynamics of lateral undulation in legged terrestrial locomotion Fabio Giardina, L Mahadevan Although undulatory locomotion is commonly associated with limb-less animals such as snakes, there exist instances of slender multi-legged animals where undulation is also observed. In centipedes, for example, lateral body undulations emerge when they move fast, although the causes for the appearance of undulations have not been unequivocally clarified. A key unresolved question is whether undulation in myriapod locomotion arises due to the natural dynamics of the organism or if it is neurally enforced. To answer this question, we developed and studied a dynamical model that accounts for biologically plausible leg kinematics and morphologies. The insights obtained from the model analysis will be presented together with their implications for the evolution of locomotor morphology in many-limbed organisms, the principles of propulsion in terrestrial locomotion, and the design of robotic locomotion systems. |
Monday, March 4, 2019 9:12AM - 9:24AM |
A65.00005: Inertial Tail-like Appendage Use in Quadrupeds Improves Stability in Diagonal Sequence Walking Gaits Haosen Xing, Baxi Chong, Guillaume Sartoretti, Julian Whitman, Yasemin Ozkan aydin, Daniel Goldman, Howie Choset There are two main sequences of footfall patterns for quadrupedal walking: lateral, adopted by most quadrupedal animals, and diagonal, preferred by quadrupedal primates. We observe that, compared with the lateral sequence (LS) gait, the diagonal sequence (DS) gait produces a larger stride displacement (i.e., higher average speed) but at the cost of decreased body stability. This work aims to increase the stability of the DS gait by investigating the use of an inertial tail-like appendage. We model this actuated tail as a multi-link manipulator whose dynamics describe how the system moves in response to joint torques. Employing a Lagrangian analysis, we derive tail oscillations that can resist the gravitational torque that drives the system off-balance. We validate our approach on a servo-based quadruped robot with an actuated tail, and compare the stride displacements of the LS and stabilized DS gaits. There, we experimentally show that with the help of an actuated tail, such a quadruped can take advantage of the higher stride displacement ( larger) of the DS gait while maintaining stability. Future work will consider the use of an actuated tail to stabilize locomotion on unstructured terrain, as well as to balance dynamic trotting gaits. |
Monday, March 4, 2019 9:24AM - 9:36AM |
A65.00006: Active sensing of particles suspended in unsteady flow Daisuke Takagi, J. Rudi Strickler Animals can generate highly unsteady flow around their body. We explore how the flow on their mechanical sensors may help in remotely detecting and locating particles suspended in the surrounding fluid. A simple analytical model demonstrates the basic physical principle, which is analogous to active sonar except with flow instead of sound. The model shows that particle-induced fluctuations in pressure or shear on the sensors can be used to reconstruct a hydrodynamic image revealing the size and position of the particle. Our findings suggest that a variety of organisms and devices may actively agitate their surroundings to enhance their sensory range. |
Monday, March 4, 2019 9:36AM - 9:48AM |
A65.00007: Kuramoto Model of Weakly Conformed Oscillators Hung-Yi Ly, Kuo-An Wu, Huan-Yu Kuo Conformity is a common phenomenon which is observed in social psychology, group decision making, and animal behavior. Inspired by the experiments of Moiseff and Copeland, in which they found that the response of female Photinus carolinus to computer flashes depends grossly on the synchrony of flashes, we consider a Kuramoto model with weakly conformed oscillators to study the effects of conformity on synchronization. In our model, the tendency of individual oscillator catching up each other varies with the degree of synchronization that mimics the conformity effect. While considering unimodal frequency distribution, a hysteresis loop emerges in the bifurcation diagram and the branch of unstable fixed points corresponds to the threshold, or "quorum", over which systems move toward more synchronized states. This result is similar to quorum response of consensus decision making, which a consensus decision is finally reached by entire group (oscillators reach synchronized states) once the population supporting it exceeds a quorum (once the degree of synchronization exceeds the threshold) |
Monday, March 4, 2019 9:48AM - 10:00AM |
A65.00008: Geometric mechanics and locomotion in dissipative environments Jennifer Rieser, Henry Astley, Joe Mendelson, Chaohui Gong, Jin Dai, Baxi Chong, Perrin Schiebel, Yasemin Ozkan aydin, Alex M Hubbard, Jeffrey W Rankin, Krijn Michel, Alfredo Nicieza, John R Hutchinson, Ross L Hatton, Howie Choset, Daniel Goldman Sustained movement through complex terrain arises from the coupling of environmental interactions with cyclic self-deformation patterns generated by animals. Using both biological experiments and mathematical modeling, we explore the importance of body coordination and morphology for both limbless and limbed animals moving though a widely-encountered environment: on and within sand. Given the highly-dissipative nature of sand, we model environmental forces using granular resistive force theory (RFT) and use geometric mechanics (GM) to map local body deformations to body-frame displacements. We find that undulatory snakes and lizards swimming within sand use waveforms that produce near-maximal displacements per undulation cycle. Recently, we have found that granular RFT also applies to movement at the surface of dissipative materials, even when contact is intermittent. We apply surface granular RFT and GM to animals with cyclic ground contact patterns (e.g., legged locomotors). We find that the coordination between foot placement and spinal flexion observed in walking salamanders produces near-maximal displacements per gait cycle. These results highlight the broad applicability of these tools to understand coordination and self-deformation patterns in dissipative environments. |
Monday, March 4, 2019 10:00AM - 10:12AM |
A65.00009: Behavioral pattern transitions and habituation to pulsed mechanical vibration in crawling Drosophila larvae Alexander Berne, Tom Zhang, Anggie Ferrer, Joseph Shomar, Tomoko Oyhama, Mason Klein How the brain receives, stores, and deploys information to create an adaptive response depends on external stimuli. Mechanical vibrations affect animal behavior, and are useful tool for understanding the correlation between neuron function and response. Using the Drosophila larva model system, a slow-moving animal with readily quantifiable behavior, we elicit a discrete set of observable avoidance responses: pause, turn, and reversal (strong) with vibration. We characterize in detail how each response type depends on vibration timing (pulse spacing and duration) and intensity (frequency and amplitude). Through precise larva tracking, we find that intensity above a threshold value increases the frequency of the reverse crawl behavior. Stimulus timing affects the probability of the each behavior: both prolonged and repeated vibration bursts over time reduce the proportion of animals reverse crawling (habituation). Additionally, memory deficient fly mutants show altered responses to repeated and sustained vibrations, suggesting the possible mechanism underlying habituated response. Drawing an analogy to a capacitor charging circuit, we model the possible relationship between biological mechanisms and habituated behavior in general. |
Monday, March 4, 2019 10:12AM - 10:24AM |
A65.00010: WITHDRAWN ABSTRACT
|
Monday, March 4, 2019 10:24AM - 10:36AM |
A65.00011: Comparative undulatory locomotion in complex environments Kelimar Diaz, Perrin Schiebel, Jimmy L Ding, Hang Lu, Daniel Goldman Despite the difference in size, slithering animals from mm scale nematodes to m scale snakes are resistive-force dominated systems. These animals press lateral body bends against heterogeneities in their surroundings to overcome drag on the elongate, limbless body. To search for general principles of control in undulatory locomotion we studied the desert-specialist C. occipitalis and the nematode C. elegans traversing sparse lattices of rigid cylindrical posts, a model heterogeneous terrain. We challenged C. occipitalis to move through square arrays of 0.64 cm diameter posts embedded in a low-friction substrate and C. elegans with fluid filled PDMS lattices of comparable size. Both animals used a waveform which was largely preserved throughout a trial resulting in bouts of locomotion-when the body contacted an opportune obstacle-interspersed with large-slip-when the substrate alone provided propulsion. C. elegans’ performance was comparable to C. occipitalis; when the animals did not contact posts they moved at ~0.2 body lengths per cycle (BL/cyc) while when they were in contact with the posts they moved at ~0.35 BL/cyc by bouts of motion. This suggests the strategies employed by both animals were similar despite the difference in size. |
Monday, March 4, 2019 10:36AM - 10:48AM |
A65.00012: Accurate quantification of bumblebee foraging David Hofmann, Ahmed Roman, Donna Rosa McDermott, Berry Brosi, Ilya Nemenman Bumblebees have been shown to learn simple forms of tool use and to transmit these skills to other members of the colony. They are thus an excellent animal model system to study learning and social interactions. However, such studies are complicated by the difficulty of precisely quantifying bumblebee behavior and interactions with the environment even in simple tasks, such as foraging. To address this, we designed a flight chamber with 3D printed artificial flowers to accurately quantify individual and collective bumblebee foraging. A radio frequency identification (RFID) system is employed to identify the individual foragers and detect their presence in flowers. A microfluidic system releases carefully controlled sucrose solution droplets of varying sizes in each flower in response to the presence of specific bees, and we then detect when the droplets are consumed. We quantify individual foraging behavior of naive bees exposed to two flowers with different reward probabilities in the course of multiple days. This mimics the setting of the well studied two-armed bandit problem in behavioral economics. We analyze the operant learning of the relation between a flower and a reward probability by the bees, and we compare the observations to predictions of various theoretical models. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700