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[Forum] Dr. Yoshiyuki YAMADA, Department of Basic Neurosciences, School of Medicine, University of Geneva

“ Context- and output layer-dependent long-term ensemble plasticity in a sensory circuit ”

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March 30, 2017 14:00 - 15:00


BSI Central Building 1F Seminar Room


Sensory information is translated into ensemble representations by various populations of projection neurons in brain circuits. The long-term dynamics of ensemble representations formed by distinct channels of output neurons in diverse behavioral contexts remains largely unknown. In the olfactory bulb (OB), mitral and tufted cells constitute two output layers that receive excitatory inputs from olfactory sensory neurons in common glomeruli, and in turn send output projections to distinct cortical and subcortical regions of the brain. Here we studied the long-term plasticity of their odor responses using chronic two-photon calcium imaging in awake behaving mice.
Both output populations displayed similar odor response profiles with relatively balanced excitation and inhibition. During passive sensory experience, both populations showed reorganization of ensemble odor representations: initially active neurons changed their response polarity or became non-responsive, and initially non-responsive neurons became active. Despite this dynamic reorganization, pattern separation remained stable across days. Intriguingly, during active odor discrimination learning, mitral but not tufted cells exhibited improved pattern separation, although both populations again showed reorganization of ensemble representations. A computational model of olfactory circuitry suggests that cortical feedback on OB interneurons can trigger both forms of plasticity.
In conclusion, we show that different OB output layers display unique context-dependent long-term ensemble plasticity, allowing parallel transfer of non-redundant sensory information to downstream centers.

Ref. Neuron 93: 1198–1212(2017) Nature Methods 7(9): 729-32. (2010)

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Katsuhiko Mikoshiba [Katsuhiko Mikoshiba, Developmental Neurobiology ]
Name: Rinkei Okano