Oscillatory Network Activity in the Accessory Olfactory Pathway: Mechanistic Basis and Functional Implications II

• Applicant: Professor Dr. Marc Spehr
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells ; Cognitive, Systems and Behavioural Neurobiology
• Term: since 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 378028035

For mammals, chemosensation is an essential sensory modality. Its importance is underscored by the presence of multiple chemosensory subsystems. Of these, the vomeronasal system (VNS) has evolved to processing cues related to social and other innate behaviors. The first brain region of the VNS is the accessory olfactory bulb (AOB). Although the AOB shares gross similarities with its main olfactory system counterpart, there are major differences between the structures. Several of the prominent and unique features of VNS signaling involve the temporal dimension. Specifically, stimulus uptake, sensory processing, and the temporal scales of downstream targets are all significantly slower compared to other sensory systems. Unlike the main olfactory system, where activity is tightly coupled to breathing, vomeronasal neurons are isolated from the breathing cycle. Yet, despite the absence of direct respiration-linked inputs, the temporal dimension, and specifically, oscillatory activity, plays a central role in vomeronasal physiology. The present research focuses on two distinct (but potentially related) phenomena, both of which indicate that oscillations are a prominent and integral feature of VNS function. Both involve AOB mitral cells (AMCs), which are a key node in VNS information processing. Specifically, AMCs sample information from sensory neurons in the vomeronasal organ, and relay outputs to downstream limbic regions including the amygdala. The first phenomenon includes infra-slow spontaneous oscillations (ISSOs) which we initially discovered in brain slices, and later in anesthetized and awake mice. The second involves local field potential oscillations that occur in response to stimulus presentation (stimulation induced local field potential oscillations, SILOs). In many brain regions, neuronal oscillations coordinate the activity of neuronal ensembles. The significance of both ISSOs and SILOS is their ability to temporally organize the joint activity of AMCs ensembles, and thus to shape distributed representations of social and other chemosensory stimuli. During the first period of this research, we established a detailed phenomenological account of ISSOs and SILOs in particular contexts, and began to explore the underlying mechanisms. In the present proposal, we build upon these foundations, to (i) reveal how these oscillations are modulated in various behavioral contexts, (ii) deepen our understating of the underlying mechanisms, and most importantly, (iii) explore their effects on more advanced vomeronasal processing stages. In a broader perspective, our research will not only shed light on the mechanisms of chemosensory processing in a social context, but also more generally, on the role of temporal coding and network oscillations in neuronal information processing.

• DFG Programme: Research Grants
• International Connection: Israel
• International Co-Applicant: Professor Dr. Yoram Ben-Shaul