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State dependent flow of excitation and activation of inhibition in cortical columns

Final Report Summary - IMAGING COLUMNS (State dependent flow of excitation and activation of inhibition in cortical columns)

Summary: In the course of the project, we have developed state of the art behavioral, and optical monitoring techniques, and have begun to combine these innovations for imaging activity flowing throughout a cortical column. We have published one paper with on an Air-track system. We have submitted two other papers, one using CaMPARI – a novel calcium indicator, and a second one that describes a novel method for monitoring behavior. These developments take us beyond the current state of the art for the study of behavior and function of cortical neurons. Our work has fostered multiple local and international collaborations. These developments reflect well on my integration within the within Neurocure Center for excellence, Humboldt Universitaets Berlin and in the end they reflect well for my continued development as a neuroscientist.
Project Objectives: The first aim of this project was to study context dependent activation of excitatory and inhibitory neurons in different laminae. The second specific aim was to image activity in the soma and dendrites pyramidal cells. To achieve these aims, we had several tasks to complete. First, among them was to establish methods for implanting and using 1-1.5 mm prisms in Berlin. Second, was to establish behavioral methods where the context changed, and establish methods for measuring the moment-to-moment changes in context. Third, was to establish the various transgenic lines that can be used for imaging neurons in different layers, and to measure signals in particular layers, and from specific classes of neurons.

Advancement beyond the state of the art:
1. We have developed the ability to monitor the details of animal behavior – the sequence of movements the animal makes during task performance – and can reward the animal, or turn on an optogenetic stimulus on the basis of a movement of a particular whisker on one trial, and another whisker on a second trial. These methods are beyond the current state of the art. While it has been possible before our work, to use cameras and videography to track motion offline, it has not been possible to use standard video-graphic methods for generating feedback online. Also note that while it is possible to monitor motion of the animal at a particular location – whisker motion to a particular point, or a nose poke to a feeder -- these approaches are limited to particular contexts. Our developments for monitoring behavior take us beyond the current state of the art because they make it possible to monitor the motion of feet and of individual whiskers online and offline.
2. A second development that is beyond the state of the art is the development of an air track – a table that floats on air.
3. We are using CaMPARI (see above). We have a paper under review and have discovered a novel cortical circuit using CaMPARI.
4. Note that we can now simultaneously detect and track the motion of multiple whiskers, forepaw, hind paw. These developments in monitoring behavior are a necessary precedent for the project. They make it possible to relate elements of complex behavior to calcium signals generated in different layers of cortex.

Transfer of Knowledge:
In the course of my work here, I have deployed new calcium indicators, and tract-tracing agents and in doing so I have worked within the Larkum lab, and have established collaborations with the Schmitz lab for 2-photon imaging, and Rosenmund lab for development of viral vectors. As with all collaborations, knowledge that is gained is shared amongst the groups. The transgenic lines that we have established for calcium imaging have also been shared within the multiple groups in Berlin.

Impact: The impact of the work being carried out under the Marie Curie fellowship can be felt in multiple areas. The main impact of the Marie Curie fellowship is that it has made it possible for us to carry out innovative experiments that will have an impact on neuroscience research. There will be a minimum of 3 (published and currently submitted papers) and up to 6 publications that arise out of this work.
We expect that our developments in monitoring behavior -- using special, but cheap and readily available camera systems -- to become integral for day to day work in many neurophysiology and behavior laboratories. We expect the air track to become the state of the art for presenting tactile worlds – plus mazes, circular mazes, linear tracks, or even different objects -- to head fixed animals. We expect to continue to develop uses for implanted prisms. We are using prisms for 1 photon imaging, and expect to use it for targeted somatic and dendritic patching, and for modulating the activity of small groups of cells. The fellowship has fostered multiple collaborations within Berlin, including those with Michael Brecht, Dietmar Schmitz, Friedrich Johenning, Christian Rosenmund. It has also fostered international collaborations with Eric Schrieter and Loren Looger at Howard Hughes Institute (Janelia in USA).

Transfer of Knowledge:
In the course of my work here, I have also established and been part of a team that includes, undergraduate, masters and PhD students in Larkum Lab. With them we have developed novel and easy to use methods for behavioral measurements. I have trained one student who is part of the Erasmus program and am training one HU Berlin undergraduate student, and two masters students who are at Humboldt University.

As a Marie Curie ambassador, I have given six invited talks about my work: in Berlin, Budapest, Paris and Copenhagen. I have given 18 hours of lectures and demonstrations to students at Charite and Humboldt University. To disseminate my work, I have created a webpage within the Larkum home page – -- and at two other online cites including Researchgate and Google Scholar. The HU-Berlin Larkum lab web page acknowledges the support of Marie Curie and the EU.

I will have been a coauthor on five presentations at the Society for Neuroscience meeting.