Abstract:
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\r\nA large fraction of behavior and cognitive neuroscience have been influenced by reinforcement learning theory. However, behavior also happens in the absence of reward. I will explain how concepts of reinforcement learning can be translated to situations and how novelty and surprise can act as internal brain signals, similar to, but distinct from the TD-error signals used in reinforcement learning [1-4]
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\r\n[1] W. Gerstner, M. Lehmann, V. Liakoni, and J. Brea (2018)
\r\nEligibility traces and plasticity on behavioral time scales: experimental support of NeoHebbian three-factor learning rules.
\r\nFront. Neural Circuits, 12:53 doi: 10.3389/fncir.2018.00053
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\r\n[2] A. Modirshanechi, J. Brea, and W. Gerstner (2022)
\r\nA taxonomy of surprise definitions
\r\nJ. Mathem. Psychol. 110:102712, DOI: 10.1016/j.jmp.2022.102712
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\r\n[3] A. Modirshanechi, W.-H. Lin, H.A. Xu, M. Herzog, and W. Gerstner (2025)
\r\nNovelty as a drive of human exploration in complex stochastic environments
\r\nProc. Natl. Acad. Sci. (U.S.A), 122:e2502193122 DOI 10.1073/pnas.2502193122
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\r\n[4] H.A. Xu, A. Modirshanechi, M.P. Lehmann, W. Gerstner, M.H. Herzog (2021)
\r\nNovelty is not Surprise: Human exploratory and adaptive behavior in sequential decision-making
\r\nPLoS Comput Biol 17: e1009070. doi: https://doi.org/10.1371/journal.pcbi.1009070
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\r\n[5] V. Liakoni, A. Modirshanechi, W. Gerstner, and J. Brea (2021)
\r\nLearning in Volatile environments with the Bayes Factor Surprise
\r\nNeural Computation 33: 1-72
Many species live in groups and coordinate behavior with conspecifics, but the sensory computations that allow individuals to detect, evaluate, and respond to others remain difficult to study. A major challenge is that social interactions are reciprocal: animals continuously change each other’s sensory experience, making it hard to separate stimulus, perception, internal state, and behavioral response.
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\r\nIn my lab, we use juvenile zebrafish shoaling as an experimentally accessible model for vertebrate social behavior. Using virtual reality, we previously identified self-like biological motion as a visual trigger of shoaling and traced this signal into a tecto-thalamic pathway that contributes to social attraction. We now build on this framework to ask how elementary visual cues are combined into richer social representations.
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\r\nI will discuss two examples. In one project, behavioral experiments and neural recordings suggest that zebrafish evaluate group size through an integrated visual variable that combines object number and motion, so that faster small groups can become behaviorally equivalent to slower larger groups. In another, we study social buffering: the reduction of fear-related behavior by conspecific cues. Here, social information can either transmit immediate alarm or provide persistent safety, depending on context. Whole-brain activity mapping reveals neural correlates of fear state and its suppression by social cues.
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\r\nTogether, these projects show how controlled visual stimuli, quantitative behavior, whole-brain activity mapping, and cellular-resolution imaging can reveal how animals transform simple sensory features into social decisions. More broadly, this work aims to understand how nervous systems extract meaning from the motion and presence of others — from detecting social cues to finding safety in numbers.
Abstract:
\r\nOlfactory navigation emerges from dynamic interactions among sensory input, brain activity, and the animal’s own movements. In C. elegans, a compact nervous system enables brain-wide imaging in behaving animals exposed to controlled olfactory environments, and undulatory locomotion reduces navigation to transitions among forward runs, reversals, and turns. Here, we used brain-wide tracking microscopy to record neural activity in freely crawling worms navigating spatial odor gradients or isotropic environments, and in immobilized worms responding to temporal odor pulses. Across conditions, we identified strongly correlated brain-wide activity patterns spanning olfactory sensory neurons, interneurons, and premotor neurons. Motor-state transitions and brain-wide correlation structure differed between freely moving and immobilized animals, demonstrating that olfactory sensory representations depend jointly on sensory input, motor activity, and behavioral context. Together, these findings show that brain-wide representations of olfactory behavior are extensively reconfigured by sensory input, self-motion, and behavioral context.
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Biofilm is an important lifestyle of bacteria where bacterial cells collectively form surface-associated aggregates embedded in a polymeric matrix they secrete. Important in industry and medicine, biofilms also represent a unique form of growing active matter with unique physical and material properties. In this talk, I will highlight our recent work on developing a platform for imaging live, growing biofilm at single-cell resolution, using Vibrio cholerae as the model organism. I will show how bacterial cells physically communicate with each other and the environment to form ordered architecture reminiscent of liquid crystals. Moreover, I will talk about our recent discovery that heterogeneity in gene expression leads to unexpected pattern formation in biofilm through a drag-based sorting mechanism. I will also highlight ongoing research in the lab on extending the imaging capability to more natural environments including marine animal hosts. I will end by showing our recent findings on the mechanical properties of the extracellular matrix that underlie the architecture of the biofilm.
","image_description":"","creation_date":"2026-05-05T13:16:32","last_modification_date":"2026-05-05T13:17:16","link_label":"","link_url":"","canceled":"False","cancel_reason":"","place_and_room":"SV 1717","url_place_and_room":"https://plan.epfl.ch/?room==SV%201717","url_online_room":"","spoken_languages":["https://memento.epfl.ch/api/v1/spoken_languages/2/?format=json"],"speaker":"Professor Jing Yan, Assistant Professor, Molecular, Cellular and Developmental Biology, Yale University","organizer":"Professor Alexandre Persat","contact":"elke.holderbeke@epfl.ch","is_internal":"False","theme":"","vulgarization":{"id":1,"fr_label":"Tout public","en_label":"General public"},"registration":{"id":3,"fr_label":"Entrée libre","en_label":"Free"},"keywords":"","file":null,"icalendar_url":"https://memento.epfl.ch/event/export/120654/","category":{"id":1,"code":"CONF","fr_label":"Conférences - Séminaires","en_label":"Conferences - Seminars","activated":true},"academic_calendar_category":null,"domains":[],"mementos":["https://memento.epfl.ch/api/v1/mementos/9/?format=json","https://memento.epfl.ch/api/v1/mementos/111/?format=json"]},{"id":71707,"title":"QSE Center Spring Assembly","slug":"qse-center-spring-assembly","event_url":"https://memento.epfl.ch/event/qse-center-spring-assembly","visual_url":"https://memento.epfl.ch/image/33033/200x112.jpg","visual_large_url":"https://memento.epfl.ch/image/33033/720x405.jpg","visual_maxsize_url":"https://memento.epfl.ch/image/33033/max-size.jpg","lang":"en","start_date":"2026-05-29","end_date":"2026-05-29","start_time":"14:00:00","end_time":"16:00:00","description":"The QSE Center Spring Assembly will take place on Friday May 29, 2026, from 14h-16h in CM 1 105. This event is an opportunity to bring the EPFL quantum community together and to share the breadth of our activities and collaborations.
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\r\n14h00-15h00: Flash talks – Eleven 5-minute talks will be given by a range of different QSE Center stakeholders including students, researchers, and internal and external collaborators.\r\n
Please join us for the Junior Quantum Seminar with Gaia Bolognini from the Laboratory for Quantum Gases (LQG), IPHYS, EPFL who will give the talk \"Density Wave Ordering in Strongly Interacting Fermi Gases\" and Emanuele Tirrito from the Laboratory of Theoretical Physics of Nanosystems (LTPN), IPHYS, EPFL who will give the talk \"Quantum Complexity in Many-Body Systems: From Entanglement to Magic\" on Tuesday June 2nd from 9h30-11h.
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\r\nPLEASE NOTE: The Junior Quantum Series are for gathering the junior quantum community of master's students, PhDs and post-docs at EPFL, to create a non-judgmental space were scientific ideas can be shared between peers. This event is not for Professors or senior researchers.
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\r\nABTRACT:
\r\n1. Density Wave Ordering in Strongly Interacting Fermi Gases
\r\nAnalog quantum simulations using ultracold atoms offer exciting opportunities to investigate many-body systems in highly controllable and tunable settings. While most studies have focused on simulation of systems with short-range interactions, their interplay with long-range interactions remains largely unexplored.
\r\nIn our experimental platform, the atomic ensemble is strongly coupled to a high finesse optical resonator, whose photons mediate an effective long-range interaction among the particles. Upon reaching a critical long-range interaction strength, the system undergoes a phase transition into a density wave ordered state, characterized by the superradiant build-up of the cavity field and the atomic self-organisation into a crystalline lattice. While this phenomenon has been extensively studied in bosonic quantum gases, we explore the effect of this transition in a degenerate two-component Fermi gas with tunable short-range interactions.
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\r\nI will present our recent experimental results, where high-resolution microscopy yields the first real-space observation of the periodic density modulation characterizing the density-wave ordered state. Moreover, the micrometer-scale resolution gives access to high-frequency spatial correlations of the gas in both the density and magnetization observables, and enables precise shaping of the trapping potential - significantly expanding the degree of control over the many-body state.
\r\nWe make use of this versatile platform to explore the interplay between the cavity field and the atomic ordering and to investigate how the many-body state of the paired Fermi gas is reshaped by the cavity mediated long-range interactions.
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\r\n2. Quantum Complexity in Many-Body Systems: From Entanglement to Magic
\r\nUnderstanding what makes a quantum many-body state complex is a central question in quantum information, quantum computation, and condensed matter physics. Traditionally, entanglement has played a central role in this discussion: it captures genuinely quantum correlations, constrains classical simulability, and provides a powerful diagnostic of phases of matter and out-of-equilibrium dynamics. However, entanglement alone does not fully characterize the computational complexity of quantum states. In particular, highly entangled states can sometimes be efficiently simulated, while universal quantum computation requires an additional resource known as magic, or non-stabilizerness.
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\r\nIn this talk, I will give a broad introduction to quantum complexity in many-body systems, focusing on the complementary roles of entanglement and magic. I will explain the physical meaning of magic, its connection to stabilizer states and Clifford circuits, and why it is necessary for quantum computational advantage. I will then discuss how magic can be generated and diagnosed in many-body dynamics, and how it provides new insight into questions such as thermalization, quantum chaos, transport, and classical simulability.
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\r\nBIO:
\r\nGaia Bolognini is currently a third year PhD student in the Laboratory for Quantum Gases (LQG) at EPFL under the supervision of professor Jean-Philippe Brantut. Her research focuses on atomic interacting matter, quantum gases and cavity quantum electrodynamics. She obtained her Master's degree at EPFL, where she focused on the assembly and the design of a new technology for quantum gas experiments, the 'cavity-microscope'. She obtained her Bachelor's degree at University of Milano-Bicocca, in my hometown.
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\r\nEmanuele Tirrito obtained his Master’s degree in Physics from the University of Pisa, working on relaxation and prethermalization in one-dimensional quantum systems. He then completed his PhD at ICFO in Barcelona, where he studied topological phases of matter and developed tensor-network methods for strongly correlated systems. After postdoctoral positions at SISSA, the University of Trento, and ICTP, his research has progressively moved toward quantum information aspects of many-body physics, with a particular focus on entanglement, non-stabilizerness or “magic”, measurement-induced transitions, and quantum simulation. He is currently an SNSF Postdoctoral Fellow at EPFL.
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This day is an opportunity for architecture students from the 2nd year Bachelor to the 2nd year Master to attend presentations of the studio and teaching unit programmes, to enable them to choose their options and finalise their enrolments.There will be no online replay and the event is not recorded. The presentation documents are available on the dedicated pages:
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\r\nDesign studios and teaching units ↗︎
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\r\nRegistration dates ↗︎