Neuronal networks form spatio-temporal activity patterns, i.e. neurons "fire" in an organised and coordinated manner and thus form functional "ensembles" or "assemblies". These assemblies can remain stable over a long period of time and can be reactivated in suitable situations. A guiding principle of modern neurophysiology is that neuronal ensembles are the physical correlate of cognitive and behavioural processes at the network level.
Our guiding questions are:
- Which mechanisms determine whether a neuron is active or inactive in a given situation (focus: CA1 pyramidal cells of the mouse hippocampus)?
- How do coordinated oscillatory activity patterns develop (focus: sharp wave-ripple complexes in the mouse hippocampus)?
- How do the numerous sub-networks of the hippocampal-entorhinal system differ (focus: deep layers of the medial entorhinal cortex)?
- Which mechanisms contribute to the coordination of networks in the entire brain (focus: gobal rhythmogenesis through respiration)?
- Further questions arise from collaborations, especially in pathophysiological contexts (Alzheimer's disease, multiple sclerosis, hypoxia).
Finally, we are also active in higher-level contexts, e.g. in the discussion on cognition and consciousness in plants.
Neuronal ensembles: From a large number of nerve cells, e.g. in the hippocampus or neocortex, only a few are active at any one time ("sparse coding"). They are integrated into a common rhythm, in the genesis of which inhibitory interneurones play a key role (red cell in the upper part of the image). In the example, the interneuron is continuously active (red trace in the lower part of the image) and thus causes rhythmic activity in the entire network (visible in the "local field potential" measured extracellularly, lower trace). Based on this network oscillation, spatio-temporal patterns of activity of the selected neurones are then formed (in the example a sequence green --> orange --> blue).