Mammals learn a large repertoire of novel actions by refining variable movements into precise skills. The brain achieves this by assigning credit to movements that led to desired outcomes. Even for simple actions such as reaching to a spatial target, the brain could assign credit to the direction, endpoint target location, speed, etc. As such, different movement strategies may emerge across individuals, depending on what is assigned with credit.

My goal is to dissect the sensorimotor areas controlling different aspects of these movements, and probe what determines the learning and control of different reach strategies. I developed a behavior task in which head-fixed mice generate exploratory forelimb trajectories with a joystick and are rewarded when they hit a hidden target in the workspace. As mice learn, they refine their target reaches which become less variable in direction, tortuosity, speed, and targeting precision. I show that different aspects of the reach such as direction or speed are learned and controlled through distinct cortical and thalamic networks. For instance,
sensorimotor cortex is required to generate reaches with high directional variability across different positions of the workspace, while a specific nucleus of thalamus is required to refine the overall reach direction.

But what reach strategies are mice learning? By relocating the start position in a small number of probe trials I discovered that some animals learned a direction-based strategy (move in the same initial direction from new starts), while others learned an endpoint-based strategy (guide the joystick into the target from new starts, adjusting their direction). Which strategy an individual animal learned correlated with the degree of spatial directional variability during exploration, the aspect of the reach controlled by cortex. This correlation is also recapitulated by model-free reinforcement learning agents trained in a similar task. Overall, these findings suggest that the sensorimotor system learns different control strategies by exploring and reinforcing certain movement aspects during learning, and that these aspects are generated by distinct circuits.

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The burgeoning field of ‘cancer-neurobiology’ centers on studying interactions among cancer, the nervous system, and cancer treatment. My recent multi-scale studies provide the first evidence that cancer and chemotherapy interact non-linearly to exacerbate neurologic disorders experienced by patients. In this talk, I will present evidence that multiple loci throughout the central- and peripheral nervous systems jointly contribute to maladaptive phenotypes. I will share results of my ongoing studies that integrate biophysical modeling, in vivo electrophysiology, kinematic evaluation, spatially informed omics, and in vivo gene knockdown to identify underlying molecular mechanism(s). Serendipitously, my studies also identified multiple pathways that link neurons to cancer. Cancer is suspected to subvert and repurpose core neuronal mechanisms to its advantage, yet little is known. I will conclude by sharing a new theme of my research program aimed at defining how these two diverse biological processes converge, with a particular interest in understanding how the nervous system responds to and influences cancer.

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Physiological mechanisms underly various aspects of animal performance, ranging from the response of individuals to environmental stressors to larger-scale migratory movements and collective behaviours. Physical factors, such as O2 level, temperature, water velocity and flow dynamics, underpin most aspects of animal locomotion, from fine-scale maneuvers to long-distance migrations. Building functional links from physiology to broader-scale biological and oceanic patterns is desirable and impactful, but faces many technological and conceptual challenges. Using a multi-faceted approach and several fish species as models, my research program aims to bridge this gap by studying physiological performance curves: how physiological performance responds to a broad range of physical and biotic factors. An individual-based hypoxic performance curve quantified the constraint of low O2 on the energetics of the fish, and the curve is plastic in European bass (D. labrax). The thermal performance curve showed that a cold-water species (rainbow trout, O. mykiss) can be acclimated to above 18 °C, the daily maxima recommended by U.S. Environmental Protection Agency, but the acclimation potential has an upper limit indicated by cardiac distress. Schooling behaviour of giant danio (D. aequipinnatus) fish downshifted their locomotor performance curve compared to a solitary individual, showing dramatic (~60%) energy saving in both laminar and turbulent flows by changing their collective kinematics. These physiological performance curves form a framework for generating a physiological performance space. Studying physiological performance spaces by integrating across molecular, organismic and ecological levels has great promise for generating functional links between physiology and broader-scale biological patterns.

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"The Evolution of Multicellularity and Cellular Differentiation" - A one-and-one-half-day symposium.

Visit Suddath Symposium website for full details and registration.

AGENDA
March 14:  1:00 - 4:45 p.m.
March 15:  8:00 a.m. - 4:10 p.m.

Few evolutionary innovations have been as impactful as the evolution of multicellularity, which opened the door to cellular differentiation and coordinated morphogenesis. Yet major gaps persist in our knowledge of how, when, and why this innovation evolved. This is due, in part, to extensive intellectual siloing that exists among developmental biologists, evolutionary biologists, paleontologists, physicists and mathematicians working on different aspects of this problem. This 32nd Annual Suddath Symposium will be focused on cutting through traditional disciplinary norms and expectations by presenting cutting-edge research that will open new routes for interdisciplinary research. 

The Suddath Symposium is held annually to celebrate the life and contribution of F.L. "Bud" Suddath by discussing the latest developments in bioengineering and bioscience. The speakers include leading researchers from around the world, and the research topic changes each year. This highly-interactive symposium has been taking place for over 30 years and is supported by the Institute for Bioengineering and Bioscience at Georgia Tech.

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Extreme environments offer a unique look into the process of adaptation since the selection pressures experienced there are often singular and strong. I will tell two stories of vertebrate adaptation to extreme environments: adaptation of a small mammal to high altitude and of a migratory fish to varying salinity environments. Using the North American deer mouse as a model, I show that adaptation to high altitude occurs through selection on existing phenotypic plasticity in aerobic metabolic performance as well as shifts in hypoxia signaling pathways that underly responses to low oxygen. Using repeatedly derived freshwater populations of a marine herring (the alewife), I show that natural selection acts on the physiological and underlying gene regulatory processes of osmoregulation to facilitate adaptation to cool, freshwater all year long. By connecting genotype-to-phenotype across biological levels of organization, my work offers a uniquely “whole-organism” perspective on the mechanisms of adaptation.

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Come join the Spatial Ecology and Paleontology Lab every Friday for Fossil Fridays! Become a fossil hunter and help discover how vertebrate communities have changed through time. Experience firsthand what it is like to be a paleontologist, finding and identifying new specimens! You will be picking and sorting 3,000 to 30,000-year-old fossil specimens from rock matrix that has been brought back from Natural Trap Cave, WY. These specimens are part of many research projects examining how the community of species living around Natural Trap Cave has changed since the extinction of the cheetahs, lions, dire wolves, mammoths, camels, horses, and other megafauna that used to live in North America. You are welcome to participate anytime that is convenient, with no commitment necessary. In fact, you can drop in or leave anytime within the two-hour timeframe. All are welcome, so bring your friends! For more information join our mailing list and/or contact Julia Schap (jschap3@gatech.edu) or Jenny McGuire (jmcguire@gatech.edu).

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Called “hilarious” by WIRED, Truth Values is also a serious exploration of the challenges women face in the STEM environment. The story follows NYC Writer/Performer and “Recovering Mathematician” Gioia De Cari’s adventures as a math Ph.D. student at M.I.T. Bewitched by the formal mathematical notion of Truth, she struggles with the clash of her personal reality in a world that is not binary.

This matinee is timed to coincide with the Gathering 4 Gardner (G4G), a biennial celebration of the legacy of beloved Scientific American writer Martin Gardner, with playful programming including math, science, puzzles, performance, magic, literature, and art.

It is not necessary to attend G4G to reserve a ticket. Seating is available on a first-come, first-served basis. To be assured a seat, please reserve asap. This event is free, reserve your ticket here.

About Truth Values

The mission of the Truth Values Community Project is to create a profoundly supportive community for women and underrepresented minorities in STEM through an innovative pairing of science, art, and conversation. 

The project was launched via sponsorship from the Alfred P. Sloan Foundation and the Massachusetts Institute of Technology.

Winner of a New York International Fringe Festival Overall Excellence Award, the play has been presented at more than 60 theaters and performing arts centers throughout the United States and Canada. Learn more at TruthValues.org/play

 Reviews for Truth Values

“Energetic, intimate, hilarious.”— Wired

"[Truth Values] is an extremely important work which deserves to be performed at every university." —Lied Center for the Arts

“Funny and insightful…replete with hilarious characters…The story is riveting...go see this show!” —CurtainUp

"Fantastic...pure humor, sadness, intelligence and struggle."
–Gigliola Staffilani, Mathematician, Member, National Academy of Sciences

“If you see only one play this year about reflexive nonbinary relations, make it this one.”— Los Angeles Times

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Microbial Experimental Evolution: social behavior, mutualism, and predator-prey interactions

Richard Lenski made microbial experimental evolution famous with his twelve flasks of Escherichia coli in minimal media, simply transferred daily without fail since 1988 for 75,000 generations in the Lenski lab.  The changes he documented along the way are monumental and occurred in the absence of any further manipulation.

Another approach to experimental evolution is to change something thought to be important and see if the predicted response occurs. This can be done in a relatively short time involving tens or hundreds of generations rather than thousands. Here I discuss several such experiments with the social amoeba Dictyostelium discoideum. This organism has a social stage in which tens of thousands of formerly independent amoebas aggregate into a fruiting body in which about 20% die to form a stalk which facilitates dispersal of the remaining 80% of hardy spores. Another attribute of D. discoideum is that it carries symbiotic bacteria which change its ability to consume bacteria.

We manipulate relatedness in the social stage to see if cooperation diminishes and then find the gene behind it. We remove the social stage to see if clones become less good at becoming reproductive spores instead of somatic stalks. We see if social stage somatic function is compromised. We make pseudo-organisms and manipulate the location of the germ line to see if cells compete to join it. We remove a symbiont to see if symbiont or host become more or less cooperative. Finally, we look at D. discoideum as a generalist predator that has costs when food bacteria change.

Taken together, these experiments show the promise of experimental evolution and the ease with which fundamental concepts in biology can be tested in microbial systems.

 

Hosted by Dr. Steve Diggle

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Scale as a unifying tool for synthesis in biodiversity studies

Some of the most important questions in biodiversity studies also remain the most controversial. Are species distributions structured by deterministic processes such as environmental filtering and species interactions, or do random processes reign supreme? Amidst a global extinction crisis, how is local biodiversity changing? How are productivity and diversity related? These and dozens of other questions have caused a considerable amount of strife in ecology over the decades. In my work, I have endeavored to find approaches, tools, data and perspectives that can synthesize these disparate views into a broader and more cohesive perspective. In this talk, I will use the concept of scale (mostly spatial, but also temporal, taxonomic ) as a fundamental mediator of biodiversity patterns and processes, and as such, as a way in which to synthesize seemingly disparate results. I will present some of the tools and approaches that we have developed that move beyond treating scale as a mere nuisance to treating it as a fundamental property of data that can help us to develop a more cohesive perspective on process and pattern in biodiversity studies. Finally, I conclude with a broader perspective on how the lessons learned in scale-dependence in biodiversity studies can help provide context for synthesis throughout ecology.

 

Hosted By Dr. Mark Hay

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Georgia Tech will be holding a high school regional competition to find the best three high school teams to be advanced to the National Science Bowl, a nationwide academic competition that tests high school and middle school students’ knowledge in all areas of sciences and math. 

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