Research Summary

Synaptic and molecular determinants controlling speed of olfactory information processing and decision making

A cardinal question in neuroscience is how the brain perceives the external world and subsequently makes the appropriate decisions that lead to specific behaviours. Of critical importance is how fast the brain can extract information, and what factors control the speed of information processing and decision-making? This research will address these questions and unravel the behavioural relevance of genetically identified inhibitory neurons in the olfactory bulb, the first stage of olfactory processing in rodents. The proposed work will combine state-of-art molecular biological, automated behavioural training paradigms with closed-loop control of neural circuits in behaving animals.

Among the mammalian sensory systems, olfaction faces the challenge of solving the highest dimensionality of stimulus space. How does the olfactory system detect and discriminate specific odours from a background of many thousands of odorant molecules?  This complex sensory processing happens at a millisecond time scale and requires excitatory neurotransmission, but inhibitory neurons effectively control, otherwise temporally limits, the excitatory neurons’ action. In the olfactory bulb (OB), granule cells (GCs) and periglomerular cells (PGs) control this synaptic inhibition. Despite limited studies, the functional relevance of different subtypes of PGs and GCs remains largely unknown and will be the focus of this project. Addressing these questions is fundamentally important, as the answers will provide a neuromechanistic insight on the olfactory information processing. They will further allow creation of a novel animal model where brain disorders associated with excitatory/inhibitory imbalance can be studied while strengthening the research on olfactory dysfunctions.

 

 

Figure Legend: A. Modification of GCs in the OB by direct stereotaxic delivery of viral vectors into the GC layer. Red square shows the Cre recombinase expressing GCs in the OB in comparison to the whole brain (DAB-stained transverse section). Scale bar 2.5 mm. Right upper corner: confocal image of a single GC (Cre expressing, labeled with mGFP). Scale bar 25 um; Abraham et al 2010. B. Mouse involved in an olfactory behavioral assay. C. Example traces olfactory responses towards a rewarded odor in a discrimination assay.