Leopoldo Petreanu

Leopoldo Petreanu
Fundação Champalimaud, Portugal
Optical dissection of cortical circuits for sensory expectations
Project leader

We can continuously make sense of our surroundings even though sensory information can be noisy and incomplete. To coherently perceive the world, our brains combine predictions learned from previous experience with incoming sensory stimuli. Where exactly in the fabric of the brain are these learned predictions stored and how they are combined with sensory stimuli remains unknown. We tested if connections linking areas of the visual cortex reflected the visual statistics of the environment. To do this, we raised mice in altered visual environments, either by rearing them in the dark or by rearing them wearing removable goggles with image-deforming optics. Using two photon microscopy and two genetically encoded calcium indicators fluorescing at different wavelengths we measured how the functional properties of individual afferent axons related to those of their target neurons. Using this approach, we tested if the functional organization of projections from high-order areas in the visual cortex reflected the visual statistics experienced by the mice. We found that, while not needed for their overall organization, visual experience deeply affected the way that connections across areas were organized. Our measurements suggest that visual experience plays and instructive role in the maturation and refinement of the connections linking visual areas, and that these connections link ensembles of neurons that are expected to be coactive given the mice experience. Given that malfunctions of the brain predictive capabilities may underlie schizophrenia and autism spectrum disorders, these results provide a deeper understanding on the role of cortical connections in perception and provide a framework for understanding their role during disease states.

Leopoldo Petreanu heads an independent research group in the Champalimaud Center for the Unknow in Lisbon, Portugal since 2011. His laboratory studies hierarchical cortical processing in the mouse neocortex. Before joining the Champalimaud Center, he did postdoctoral research at the Cold Spring Harbor Laboratory and the Howard Hughes Medical Institute’s Janelia Research Campus where he pioneered imaging and optogenetic methods to study long-range connections in the mouse cerebral cortex. He holds a Ph.D. in Neuroscience from The Rockefeller University and a degree in Biology from the University of Buenos Aires.

https://www.dropbox.com/s/37b3e860whcorhz/Petreanu_CV2022_NF.docx?dl=0

Our brain is constantly interpreting the environment around us to plan and guide our actions. This requires combining sensory inputs with internal models of the world. We study how this process emerges from networks of neurons in the mouse neocortex. Using optical, electrophysiological and behavioral methods we investigate how different cortical areas learn and store knowledge about expected regularities of the world and how it is combined with sensory information to give rise to perception.

Visual perception, mice, neocortex, two-photon imaging, optogenetics

• Broussard, G.J, Petreanu L. Eavesdropping wires: Recording activity in axons using genetically encoded calcium indicators. J. Neurosci. Methods. 360, 109251 (2021).

• Young H, Belbut B, Baeta M, Petreanu L. Laminar-specific cortico-cortical loops in mouse visual cortex. eLife. 10.7554/eLife.59551 (2021).

• Broussard, G.J., Liang, Y., Fridman, M., Unger,E.K., Meng,G., Xiao, X,, Ji, N., Petreanu, L.* and Tian, L*. In vivo measurement of afferent activity with axon-specific calcium imaging., Nature Neuroscience, 21, 1272-1280 (2018). *corresponding author.

• Marques, T., Summers, M.T., Fioreze, G., Fridman, M., Dias, R.F., Feller, M.B., and Petreanu, L. A Role for Mouse Primary Visual Cortex in Motion Perception. Current Biology. 28, 1703–1713.e6. (2018).

• Marques, T., Nguyen, J., Fioreze G., and Petreanu L., The Functional Organization of Cortical Feedback Inputs to Primary Visual Cortex, Nature Neuroscience, 21, 757-764 (2018).

Champalimaud Foundation
Avenida Brasília
1400-038 Lisboa
Portugal

https://www.fchampalimaud.org