Efficient odour representations in the olfactory bulb: Flexible lateral interactions synchronize co-active columns

How is the percept of a smell generated from the fractionated representation of odours at the periphery where olfactory receptor channels detect structural elements of odour molecules? While this problem seems akin to the detection of a “Gestalt”/object by the visual system using its contours, there is a fundamental difference between olfaction and vision due to the discontinuous, non-topographical nature of odour representation. Recently my group has discovered intriguing subcellular mechanisms of the neuronal microcircuits prevalent in the olfactory bulb that may enable flexible and energy-efficient non-topographical odour representation. These microcircuits connect distant olfactory receptor channel columns with each other and operate in a previously unknown activity-dependent manner. Here we aim to translate these findings from the synaptic to the systemic level, and test our hypotheses regarding the synchronization mechanism of co-active receptor channel columns in the gamma regime which will then allow the combinatorial synthesis of the odour percept in the olfactory cortex. By combining olfactory stimulation of our semi-intact nose-brain preparation with state-of-the-art imaging techniques with unprecedented large-scale spatio-temporal resolution (3D two-photon imaging of voltage-sensitive dyes), we will study the interaction between the neuronal ensembles belonging to columnar channels. This system-level understanding will be complemented by in-depth investigation of activity-dependent output of individual synapses in acute brain slices. Next, we will test whether columnar activity upon odour stimulation is amplified by a local mechanism recently discovered by our lab that links blood vessel pulsations to oscillatory neural activity. Finally, we will integrate our results into a realistic computational network model of the olfactory bulb. COLUMNET will significantly advance our understanding of olfactory perception.