[image: VVTNS.png] https://www.wwtns.online - on twitter: wwtns@TheoreticalWide You are cordially invited to the lecture given by Agostina Palmigiano Gatsby Unit, London on the topic of "Mechanisms underlying responses to optogenetic perturbations*"* The lecture will be held on zoom on *May 15, 2024*, at *11:00 am EDT * To receive the zoom link: https://www.wwtns.online/register-page *Abstract: *Optogenetic stimulation is a powerful tool to probe neural circuits. Yet, its effect on neural dynamics can be counterintuitive. Here, we analyzed and theoretically modeled neuronal responses to visual and optogenetic inputs in mouse and monkey V1. We found that in both species, optogenetic activation of excitatory neurons had weak or no effects on the distribution of firing rates across the population, but strongly modulated single-cell activity, a phenomenon which we call neuronal reshuffling. Through theoretical analysis and numerical investigations, we show that neuronal reshuffling emerges in strongly-coupled, randomly-connected networks via strong feedback inhibition, provided that the optogenetic input is sufficiently heterogeneous and weak. As perfect reshuffling was observed only when measuring cells whose orientation preference matched the orientation of the presented stimulus (in the monkey data), we extended our analysis to networks with a connection probability and inputs that depend on the cell's feature preference. We show that this model can be theoretically described as interactions between the tuned activity, encoding sensory features, and the untuned baseline activity. Finally, we show that these models can produce rate reshuffling via strong, effective inhibition of the tuned response by the untuned baseline and work out an intuition for this phenomenon. *About VVTNS : Created as the World Wide Neuroscience Seminar (WWTNS) in November 2020 and renamed in homage to Carl van Vreeswijk in Memoriam (April 20, 2022), its aim is to be a platform to exchange ideas among theoreticians. Speakers have the occasion to talk about theoretical aspects of their work which cannot be discussed in a setting where the majority of the audience consists of experimentalists. The seminars, **held on Wednesdays at 11 am ET,** are 45-50 min long followed by a discussion. The talks are recorded with authorization of the speaker and are available to everybody on our YouTube channel.* ᐧ ᐧ ᐧ ᐧ ᐧ ᐧ