Biology subjects

Gomez-Marin, A.

Publications and source records attributed to Gomez-Marin, A..

3 recordsLinked to original sources

bioRxiv2019

Geometric purity, kinematic scaling and dynamic optimality in drawing movements beyond ellipses

Drawing movements have been shown to comply with a power law constraining local curvature and instantaneous speed. In particular, ellipses have been extensively studied, enjoying a 2/3 exponent. While the origin of such non-trivial relationship remains debated, it has been proposed to be an outcome of the least action principle whereby mechanical work is minimized along 2/3 power law trajectories. Here we demonstrate that such claim is flawed. We then study a wider range of curves beyond ellipses that can have 2/3 power law scaling. We show that all such geometries are quasi-pure with the same spectral frequency. We then numerically estimate that their dynamics produce minimum jerk. Finally, using variational calculus and simulations, we discover that equi-affine displacement is invariant across different kinematics, power law or otherwise. In sum, we deepen and clarify the relationship between geometric purity, kinematic scaling and dynamic optimality for trajectories beyond ellipses. It is enticing to realize that we still do not fully understand why we move our pen on a piece of paper the way we do.\n\nHighlightsO_LISeveral curves beyond ellipses have power-law kinematics with 2/3 exponent.\nC_LIO_LIThe curvature spectrum of each of such geometries is quasi-pure at frequency 2.\nC_LIO_LITheir dynamics are shown to comply with minimum of jerk.\nC_LIO_LIBut the 2/3 power law is not an outcome of minimizing mechanical work.\nC_LIO_LIYet, equi-affine displacement is invariant upon different kinematics.\nC_LI\n\nGraphical abstract\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=182 SRC=\"FIGDIR/small/737460v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (19K):\norg.highwire.dtl.DTLVardef@1a14c5corg.highwire.dtl.DTLVardef@9c6338org.highwire.dtl.DTLVardef@1360763org.highwire.dtl.DTLVardef@1ef534_HPS_FORMAT_FIGEXP M_FIG C_FIG \"We must represent any change, any movement, as absolutely indivisible.\" -- Henri Bergson

animal behavior and cognition↗

bioRxiv2019

A context-free grammar for Caenorhabditis elegans behavior

Hierarchy is a candidate organizing principle of ethology, where actions grouped into higher order chunks combine in specific ways to generate adaptive behavior. However, demonstrations of hierarchical organization in behavior have been scarce. Moreover, it remains unclear how such underlying organization allows for behavioral flexibility. Here we uncover the hierarchical and flexible nature of Caenorhabditis elegans behavior. By describing worm locomotion as a sequence of discrete postural templates, we identified chunks containing mutually substitutable postures along the dynamics. We then elucidated the rules governing their interactions. We found that stereotypical roaming can be described by a specific sequence of postural chunks, which exhibit flexibility at the lowest postural level. The same chunks get combined differently to produce dwelling, capturing non-stereotypical actions across timescales. We show that worm foraging is organized hierarchically --a feature not explainable via Markovian dynamics--, and derive a context-free grammar governing its behavior --which is different than a regular grammar, or a hidden Markov chain. In sum, in making the analogy with human language concrete (but not literal) our work demonstrates, in line with the foundational insights of classical ethologists, that spontaneous behavior is orderly flexible. Once more, investigating the humble nematode suggests that everything human has its roots in lower animal behavior.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=180 HEIGHT=200 SRC=\"FIGDIR/small/708891v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (25K):\norg.highwire.dtl.DTLVardef@168e648org.highwire.dtl.DTLVardef@1e6b2eeorg.highwire.dtl.DTLVardef@ed3ecdorg.highwire.dtl.DTLVardef@1b60741_HPS_FORMAT_FIGEXP M_FIG Graphical abstract\n\nC_FIG

animal behavior and cognition↗

bioRxiv2019

A customizable tablet app for hand movement research outside the lab

BackgroundPrecise behavioral measurements allow the discovery of movement constraints that provide insights into sensory-motor processes and their underlying neural mechanisms. For instance, when humans draw an ellipse on a piece of paper, the instantaneous speed of the pen co-varies tightly with the local curvature of the path. Known as the speed-curvature power law, this phenomenon relates to fundamental questions of motor control.\n\nNew MethodWe have developed a software app for displaying static curves or dynamic targets while recording finger or stylus movements on Android touch-screen tablets. Designed for human hand movement research, the app is free, ready-to-use, open-source and customizable.\n\nResultsWe provide a template experimental protocol, and detailed explanations to use it and flexibly modify the code for different kinds of tasks. Our validation of the app demonstrates laboratory-quality results outside the laboratory. We also provide raw data and analysis scripts.\n\nComparison with Existing MethodsCommonly used laboratory devices for recording hand movement trajectories are large, heavy and expensive. In turn, software apps are often not published, nor customizable. Our app running on tablets becomes an affordable, flexible, and portable tool suited for quantitative and robust behavioral studies with large number of participants and outside the laboratory (e.g. in a classroom, a hospital, or at home).\n\nConclusionsThe affordability, flexibility, and resolution of our tablet app provide an effective tool to study behavior quantitatively in the real world.\n\nHighlightsO_LIA free, ready-to-use, open source, and customizable app for Android tablets.\nC_LIO_LIHigh-resolution measuring of finger movement during tracing, tracking & scribbling.\nC_LIO_LIFast and easy data collection and experimental design with affordable hardware.\nC_LIO_LIAllowing for high-throughput experiments outside the lab (classroom, hospital, home).\nC_LIO_LIValidated for state-of-the-art research (speed-curvature power law, drawing accuracy).\nC_LI\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=165 SRC=\"FIGDIR/small/633305v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (13K):\norg.highwire.dtl.DTLVardef@1ff34corg.highwire.dtl.DTLVardef@19e151borg.highwire.dtl.DTLVardef@17bb702org.highwire.dtl.DTLVardef@12c185b_HPS_FORMAT_FIGEXP M_FIG C_FIG

animal behavior and cognition↗