Synchronous Infra-Slow Oscillations Organize Ensembles of Accessory Olfactory Bulb Projection Neurons into Distinct Microcircuits In Vitro and In Vivo

Synchronous Infra-Slow Oscillations Organize Ensembles of Accessory Olfactory Bulb Projection Neurons into Distinct Microcircuits In Vitro and In Vivo

Poster presentation

Sebastian Malinowski ^{1, 2}, Julia Mohrhardt ^{1, 3}, Chryssanthi Tsitoura ⁴, David Fleck ¹, Brett DiBenedictis ⁵, Yuan Gao ⁵, Ian Davison ⁵, Yoram Ben-Shaul ⁶, Marc Spehr ^{1, 2, 3}

¹ Department of Chemosensation, Institute for Biology II, RWTH Aachen University, Aachen, D-52074, Germany, ² Research Training Group 2416 MultiSenses-MultiScales, RWTH Aachen University, Aachen, D-52074, Germany, ³ International Research Training Group 2150 The Neuroscience of Modulating Aggression and Impulsivity in Psychopathology, RWTH Aachen University, Aachen, D-52074, Germany, ⁴ Sainsbury Wellcome Centre for Neural Circuits and Behaviour, University College London, London W1T 4JG, United Kingdom, ⁵ Department of Biology, Boston University, Boston, Massachusetts 02115, ⁶ Faculty of Medicine, Department of Medical Neurobiology, The Hebrew University of Jerusalem, Jerusalem 91120, Israel

Controlling social and sexual behaviour, the accessory olfactory system is indispensable for most mammals. The accessory olfactory bulb (AOB) represents the first stage of information processing in the accessory olfactory system. Here, a subpopulation of mitral cells, which represent the sole projection neurons in the AOB, exhibit infra-slow periodic discharge. AOB mitral cells directly innervate regions in the medial amygdala and hypothalamus that control neuroendocrine state and / or behaviour. However, the physiological mechanisms that underlie AOB mitral cell default output remain controversial. In addition, whether rhythmic infra-slow activity patterns exist in awake behaving mice and whether such activity reflects the functional organization of AOB circuitry remains unclear. Here, we show that AOB mitral cell ensembles form synchronized microcircuits, subdividing the AOB into distinct functional clusters. Using a miniature microscope, we recorded Ca²⁺ transients within the apical dendritic compartments of large AOB mitral cell ensembles in vivo. Using Cre-loxP mouse genetics to selectively label AOB mitral cells, we show that infra-slow periodic activity patterns reflect the idle state of AOB output in awake male and female mice. In addition, confocal time-lapse imaging in acute brain slices shows that ensembles of mitral cells cluster into distinct microcircuits that exhibit correlated Ca²⁺ transients. Our results indicate that synchronous oscillatory discharge of AOB mitral cells plays a key role in information processing in the accessory olfactory system, subdividing the AOB into functional microcircuits, each characterized by a distinct default pattern of infra-slow rhythmicity.