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SFB 1134:  Functional ensembles: cellular components, patterned activity and plasticity of co-active neurons in local networks

Subject Area Medicine
Term from 2015 to 2019
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 243553651
 
Final Report Year 2020

Final Report Abstract

Perceptions, memories, thoughts, choices, actions and feelings have a physical correlate in the nervous system. Converging evidence indicates that such representations are given by the combined activity of multiple neurons. These groups of neurons, called ensembles, were the central theme of our Collaborative Research Centre. In order to understand neuronal representations we need an interdisciplinary approach towards the structure, spatio-temporal organization, cellular mechanisms, diversity, plasticity and functional role of neuronal ensembles. These studies can build on a wealth of knowledge about molecular-cellular and brain-wide systemic mechanisms, whereas concepts and tools for analysis of multi-cellular activity patterns are still emerging and constitute an own, highly dynamic field. Studying spatio-temporal activity patterns in neuronal networks would fill a major gap in understanding neuronal functions at different system levels. Indeed, it may be at the heart of the unsolved problem of the ‘neuronal code’. Our approach cut through different functional systems, brain regions, methods and models. What kept us together was the common theme of transiently stable multi-neuronal activity patterns. We followed three leading questions: i) How are selected neurons entrained by their ensemble, and how are others excluded? Here, we looked at the cellular mechanisms which link single neurons with a group of selected cells, forming a ‘meaningful’ ensemble, (e.g., synaptic plasticity, specific afferent or efferent connectivity, subcellular specializations). ii) What are the characteristic features of spatio-temporal activity patterns in different networks? We monitored multi-neuronal dynamics in different models and contexts, revealing common principles and characteristic differences (e.g., sparseness, pattern separation, temporal and spatial characteristics). These properties set important boundary conditions for the emerging systemic functions. iii) How do ensembles adapt to novel experience and to changes of inner or outer conditions? We explored adaptive and state-dependent plasticity of ensembles, a fundamental condition for successful behaviour (e.g. learning-related formation of new ensembles, effects of neuromodulators on the activation of ensembles). These systematic questions are linked by important ‘perpendicular’ motives stretching through all three system levels: What are the links between co-activity at different time scales? How does the structure of cells and networks support function? In order to tackle these questions we used and improved state-of-the-art or even new methods for monitoring, manipulating, detecting and mapping functional ensembles.

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