Correlated network activity forms computational subcircuits in the accessory olfactory bulb

• Korrelierte Netzwerkaktivität führt zur Bildung von informationskodierenden Subnetzwerken im akzessorischen olfaktorischen Bulbus

Malinowski, Sebastian Tobias; Spehr, Marc (Thesis advisor); Ben-Shaul, Yoram (Thesis advisor)

Aachen : RWTH Aachen University (2022)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2022

Abstract

Controlling social behaviour and endocrine state, the accessory olfactory system is indispensable for most mammals. Here, the AOB represents the first stage of information processing in this important, though relatively reductionist system. Surprisingly, many basic principles of AOB information processing remain elusive. In this thesis, I showed that the default activity pattern of AMCs, the sole projection neurons in the AOB, is represented by infraslow oscillations both in vitro and in vivo. In vitro, about 50% of AMCs in their idle state showed this periodic activity, whereas we observed this phenomenon in 29% of AMCs in vivo. My data reveal that temporal coupling of AMCs leads to formation of synchronized microcircuits that build functional subunits within the mitral cell layer. These ensembles enable advanced information processing by adding another temporal coding feature. In addition, pronounced rhythmic activity makes information processing more resistant against internal noise, which is of utmost importance for an indispensable system like the AOS. Furthermore, I showed the influence of inhibition via GABAergic synaptic transmission on microcircuit formation. The AOB is a target of GABAergic top-down modulation. My findings indicate a possible influence of centrifugal inputs on microcircuit formation, and therefore on AOB information processing. In addition, my work enabled AMC large scale calcium imaging in vivo at single cell resolution for the first time. I observed the presence of correlated network activity in vivo, supporting the in vitro finding of ensemble activity. Together, this approach, being able to monitor a large population of genetically targeted AMCs simultaneously without harming any olfactory brain area, lays a basis to address many pressing questions in AOS research. Here, I could show the presence of three physiologically different AMC populations: oscillating, irregularly bursting, and irregular. Thereby, I strengthen the emerging insights that AMCs are a rather heterogeneous neuron population. Further investigations, combining the experimental toolbox I established in this thesis with behavioural paradigms, will help to ultimately decipher AOS physiology.