Circuit mechanisms of cortico-cortical interactions for visual processing

• Applicant: Dr. Julia Veit
• Subject Area: Cognitive, Systems and Behavioural Neurobiology
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 423175063

Any object we perceive visually is simultaneously processed by many different visual cortical areas. For example, if we see a bird fly by, the colors of its feathers, the shape of its beak, and the direction it is flying in are all processed in separate areas. Each of these specialized areas extracts certain features of the visual image and passes the results of its local computations on to other areas. The areas are organized roughly hierarchically but communicate in both feedforward and feedback directions.While in recent years, novel, cell-type specific techniques have allowed for a much more complete understanding of the exact circuit mechanisms underlying local computations in single brain areas, we still lack a similarly detailed understanding of the interactions between different cortical areas. However, this knowledge is crucial for a holistic understanding of visual processing and perception. In my research group, we will address some of these fundamental questions on inter-areal interactions and distributed cortical computation with state-of-the-art recording techniques and optogenetic tools. Specifically, the proposed research aims 1) to understand how rhythmic activity can help signals propagate between areas and 2) to understand the role of feedback projections for visual processing and perception.We will tackle these questions using mice as out model system, which allows access to powerful optogenetic tools. For the first aim, we will use this technique to manipulate specific interneuron-types controlling the synchrony of a neuronal population to observe how this affects downstream activity. Pairing optogenetics with retrograde labelling of neurons allows to activate or suppress specifically only neurons projecting between two cortical areas with millisecond temporal precision. We will use this tool to investigate the role feedback to the primary visual cortex has in perceiving figure-ground stimuli. We will train mice on a figure detection task to be able to relate neuronal activity of specific cell-types to the mouse’s performance on a trial-by-trial basis and to test, whether suppressing feedback can bias the mouse’s perception. As a readout of neuronal activity we will use electrophysiological recordings with novel, high-density probes. These so-called Neuropixels probes allow for simultaneous sampling of unprecedented numbers of single neurons across all cortical layers. Parallel recordings in multiple visual areas will allow to understand the fine temporal patterns of synchronization across areas, how they depend on specific cell-types and how they influence each other.Taken together my research group will investigate the interactions between visual cortical areas to reach a better understanding of the mechanisms underlying distributed cortical computation and visual perception.

• DFG Programme: Independent Junior Research Groups