Bulletin of the American Physical Society
APS March Meeting 2024
Monday–Friday, March 4–8, 2024; Minneapolis & Virtual
Session PP02: V: Biological Physics at the Organismal and Population ScaleVirtual Only
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Sponsoring Units: DBIO Chair: Mirna Mihovilovic Skanata, Syracuse University; Ee Hou Yong, Nanyang Technological University Room: Virtual Room 02 |
Thursday, March 7, 2024 11:30AM - 11:42AM |
PP02.00001: Network Statistics of the Whole-Brain Connectome of Drosophila Albert Lin, Runzhe Yang, Sven Dorkenwald, Arie Matsliah, Amy Sterling, Philipp Schlegel, Szi-chieh Yu, Claire McKellar, Marta Costa, Katharina Eichler, Alexander Bates, Nils Eckstein, Jan Funke, Gregory Jefferis, Mala Murthy Animal brains are complex organs composed of thousands of interconnected neurons. Characterizing the network properties of these brains is a requisite step towards understanding mechanisms of computation and information flow. With the completion of the Flywire project, we now have access to the connectome of a complete adult Drosophila brain, containing 130,000 neurons and millions of connections. Here, we present a statistical summary and data products of the Flywire connectome, delving into its network properties and topological features. To gain insights into local connectivity, we computed the prevalence of two- and three-node network motifs, examined their strengths and neurotransmitter compositions, and compared these topological metrics with wiring diagrams of other animals. We uncovered a population of highly connected neurons known as the ``rich club" and identified subsets of neurons that may serve as integrators or broadcasters of signals. Finally, we examined subnetworks based on 78 anatomically defined brain regions. The freely available data and neuron populations presented here will serve as a foundation for models and experiments exploring the relationship between neural activity and anatomical structure. |
Thursday, March 7, 2024 11:42AM - 11:54AM |
PP02.00002: Modulation of brain waves via auditory stimuli Maximus London-Kolb, Sorinel Oprisan The four main brain wave frequencies, alpha (8-12 Hz), beta (12-35 Hz), delta (0.5-4 Hz), and theta (4-8 Hz), dominate the brain at different times and dictate varying states of consciousness. We used musing to explore how it impacts the brain's frequencies. For this purpose, we used the electroencephalogram (EEG) device from BIOPAC with three different recording channels. The EEG electrodes were placed on the frontal, temporal, and parietal regions of the brain, which are associated with emotional processing, attention, and relaxation, respectively. The EEGs were recorded for 5 minutes before and after each musical condition to capture baseline and experimental brain wave activity. The music was presented through Apple Earpods at a comfortable, fixed volume. The time of day was between the hours of 12 and 6 p.m. so that circadian differences were not too distinct between trials. The subjects were both music experts and naïve subjects without any music background or training. Classical and rock music were the primary focus to study the effect on state of mind. As alpha waves define a relaxed state of mind, it was expected that classical music would cause these types of waves to take hold. Conversely, we predicted that rock music would cause the brain to exhibit beta waves, which characterize a state of wakefulness and alertness. Delta and theta waves are only exhibited in states of extreme relaxation and/or sleep, so we predicted they are less likely to be displayed during our experiment. The data were analyzed offline with the BIOPAC proprietary AcqKnowledge 5 software package. Among other measures, we explored the Fourier spectra and determined the ratio of brain wave power in different frequency bands. |
Thursday, March 7, 2024 11:54AM - 12:06PM |
PP02.00003: A Convolutional Neural Network for Seizure Prediction using Synthetic and Electrocorticographic Intracranial Data Louis R Nemzer The ability to predict the onset of seizures would represent a significant increase in quality of life for patients with epilepsy refractory to treatment. However, the goal of accurate real-time seizure prediction has not been realized despite decades of efforts. Here, we combine intracranial electrocorticographic recordings possessing high temporal resolution from a patient database with synthetically created data to train a convolutional neural network. Using a wavelet transform, the voltage time-series data from each electrode channel can be converted into a separate image layer. The approach takes advantage of the mature ecosystem of tools for machine learning using medical images. The synthetic data is generated using a computational model of connected artificial neurons based on the Hodgkin–Huxley coupled differential equations with tunable parameters. This model has been shown to have the ability to exhibit both healthy and ictal brain function regimes with physiologically interpretable variables. The results of this work may help lead to the development of algorithms that can provide more accurate forecasts of real-time seizure risk. |
Thursday, March 7, 2024 12:06PM - 12:18PM |
PP02.00004: Comparative Analysis of Embolism Dynamics in Biomimetic Models and Adiantum Leaves Ludovic Keiser, Benjamin Dollet, Philippe Marmottant Drought poses a significant threat to global forest ecosystems by potentially disrupting sap transport in plant hydraulic systems through air embolism. The mechanisms of air entry and subsequent spread within leaf veins, known as air seeding, are not yet fully understood. Leveraging a recently developed biomimetic leaf model, we conduct a side-by-side analysis of embolism dynamics in both Adiantum (maidenhair fern) leaves with linear venation and our synthetic counterparts. Our study reveals that the intermittent, or jerky, propagation patterns observed in Adiantum leaves can be replicated in biomimetic veins through the incorporation of constrictions that simulate membrane pits found in natural leaves. We demonstrate that this intermittency can be modeled effectively by coupling pressure fluctuations caused by these pits to the volume changes in the compliant veins. Our findings set the stage for a more comprehensive understanding of embolism growth in the complex, branched vein networks of angiosperm leaves, where unique hierarchical patterns have been observed. |
Thursday, March 7, 2024 12:18PM - 12:30PM |
PP02.00005: Air invasion in a transpiring biomimetic leaf-on-chip François-Xavier Gauci, XAVIER NOBLIN, Ludovic Keiser, Céline Cohen, Philippe Marmottant, Benjamin Dollet Global warming will lead to increasingly severe droughts and threatens most of the forests across the globe [1]. Trees facing drought conditions are particularly threatened by the formation of air embolisms, which hinder the flow of sap and could ultimately result in their demise. Within the context of leaves, the occurrence of embolisms has been observed to spread intermittently and possibly result in catastrophic events [2]. The utilization of PDMS-based biomimetic leaves for simulating evapotranspiration [3] has demonstrated that in a linear configuration, the existence of a slender constriction in the channel allows for the creation of intermittent embolism propagation. This intermittent dynamics arises from the interaction between the elasticity of the biomimetic leaf's venation structure and the capillary forces at the air/water interfaces [4]. |
Thursday, March 7, 2024 12:30PM - 12:42PM |
PP02.00006: Mechanical Memory in Plants: Insights from Mimosa pudica Chantal Nguyen, Patricia Mendoza-Anselmi, Orit Peleg Plants provide a unique and experimentally amenable arena for studying the dynamics of information storage and transfer in a complex system. Mimosa pudica, or the "sensitive plant", possesses small leaflets that fold in response to touch, rapid temperature changes, and electrical stimulation, making it a desirable model plant for probing the mechanical storage and propagation of information. This behavior comes at a tradeoff, as it serves as a defense mechanism to deter herbivores, but reduces the plant's ability to photosynthesize. After being repeatedly exposed to non-damaging stimuli, the plants only partially close their leaves, if at all, and reopen them more quickly. However, the mechanism by which plants are able to store such "mechanical memory" is currently unclear. We perform a behavioral assay on Mimosa pudica plants using a controllable electrical stimulation setup to investigate how the plants' leaf-folding response varies with stimulation intensity and frequency. We use experimental observations to fit a mathematical model of leaf-folding dynamics that incorporates memory by integrating over the temporal history of stimuli. Ultimately, our results translate the behavioral and mechanical principles of Mimosa pudica to inform the design of biomimetic materials and robotic systems that can retain and retrieve mechanical memory. |
Thursday, March 7, 2024 12:42PM - 12:54PM |
PP02.00007: Unveiling decentralized feedback mechanisms in sea star locomotion using deep reinforcement learning Sina Heydari, Josh Merel, Matthew McHenry, Eva Kanso In recent years, there has been growing interest in understanding decentralized control mechanisms in biology, in part due to the increased adaptability they offer in robotics systems. Sea stars use hundreds of hydrostatic structures called tube feet for locomotion, making them an ideal model system for studying decentralized sensing and actuation. Individual tube feet are equipped with integrated sensing and actuation and their activity is orchestrated by a nerve net that is distributed throughout the body without a central brain. How the numerous tube feet are controlled and coordinated for locomotion through such a distributed nervous system remains mostly unknown. |
Thursday, March 7, 2024 12:54PM - 1:06PM |
PP02.00008: Selective social interactions and speed-induced leadership in schooling fish Andreu Puy, Palina Bartashevich, Elisabet Gimeno, Jordi Torrents, M. Carmen Miguel, Romualdo Pastor-Satorras, Pawel Romanczuk Animals moving together in groups are believed to interact via effective social forces, such as attraction, repulsion and alignment. They can be inferred using `force maps', i.e. by analyzing the dependency of the acceleration of a focal individual on relevant variables. Here we introduce a force map technique suitable for the analysis of velocity alignment interaction. After validating it using an agent-based model, we apply it to experimental data of schooling fish. We observe signatures of an effective alignment force with faster neighbors, and an unexpected anti-alignment with slower neighbors. Instead of an explicit anti-alignment behavior, we suggest that the observed pattern is the result of a selective attention mechanism, where fish pay less attention to slower neighbors. This mechanism implies the existence of temporal leadership interactions based on relative speeds. We present support for this hypothesis both from agent-based modeling, as well as from exploring leader-follower relationships in the experimental data. |
Thursday, March 7, 2024 1:06PM - 1:18PM |
PP02.00009: Inoculum-dependent instability of a biofilm pellicle is rescued by non-biofilm formers Yuya Karita, Gisela T Rodríguez-Sánchez, Elisa Brambilla, J. Carlos R Hernandez-Beltran, Michael Schwarz, Paul B Rainey Various microbes are known to colonize the air-liquid interface of an unshaken culture by forming a pellicle-like biofilm. Occupying the spatial niche at an air-liquid interface is beneficial for aerobic microbes to secure access to oxygen and thus has a big impact on ecology and evolution. Although genetic factors that drive pellicle formation, such as extracellular matrices and fimbriae, have been extensively investigated, no clear understanding of the spatio-temporal dynamics has been achieved. In this work, combining experimental and computational approaches, we studied the physical principle of bacterial colonization at an air-liquid interface and its ecological and evolutionary implications. First, we experimentally showed that pellicle formation tended to fail when starting from a low inoculum. This inoculum effect was caused by the detachment of floating microcolonies from the air-liquid interface due to physical instability. To overcome the instability, collective colonization was critical to rapidly cover the space prior to the accumulation of biomass. We further tested the role of non-biofilm formers, which had been regarded as cheaters because they produced less extracellular metrices. Strikingly, the non-biofilm formers rescued the inoculum-dependent collapse of a pellicle by providing physical support. Our results characterize the universal dynamics of pellicle formation and highlight a novel physical contribution of cheaters that do not produce common goods. |
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