It is believed that neuronal activities in the individual neuronal network module, such as barrel and column, build up the fundamental function of the network module and the mutual interaction among the network modules are reflected in the brain function. To understand the brain mechanism at the neuronal network level, it is important to clarify how individual neuronal activities are processed in the network module.
Despite much study, the functional basis of the modules has remained unclear because it is difficult to detect individual neuronal activities in the context of their neuronal networks. Applying the in vivo electroporation neuronal labeling method to the two-photon functional imaging, I am currently investigating the questions using the olfactory glomerular module as a model system. This will in turn, allow us to understand not only the basic function the glomerular module plays in odor coding and smell perception but also the general functional rule of the neuronal network modules.
Neurons associated with a single glomerulus were visualized using our developed in vivo electroporation labeling method. These images were captured by two-photon microscopy and aligned from the surface to the deep part of the olfactory bulb. These methods allow for visualizing and detecting not only the multiple neuronal morphologies but also their neuronal activities. Now we are attempting to detect the neuronal ensemble activities within an intra- and inter-neuronal network unit to understand how individual neurons process the information in the context of the neuronal circuit using olfactory system as a model.
Kikuta S., Fletcher M.L., Homma R., Yamasoba T. & Nagayama S. Odorant response properties of individual neurons in an olfactory glomerular module. Neuron (2013) 77:1122-1135
Igarashi K.M., Ieki N., An M., Yamaguchi Y., Nagayama S., Kobayakawa K., Kobayakawa R., Tanifuji M., Sakano H., Chen W.R. & Mori K. Parallel Mitral and Tufted Cell Pathways Route Distinct Odor Information to Different Targets in the Olfactory Cortex. J. Neurosci. (2012) 32(23): 7970-7985
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Nagayama S., Shaoqun Z., Xiong W., Fletcher M.L., Masurkar A.V., Davis D.J., Pieribone V.A. & Chen W.R. In vivo simultaneous tracing and Ca2+ imaging of local neuronal circuits. Neuron (2007) 53: 789-803.
Takahashi Y.K., Nagayama S. & Mori K. Detection and masking of spoiled food smells by odor maps in the olfactory bulb. J. Neurosci. (2004) 24(40): 8690–8694.
Nagayama S., Takahashi Y.K., Yoshihara Y. & Mori K. Mitral and tufted cells differ in the decoding manner of odor maps in the rat olfactory bulb. J. Neurophysiol. (2004) 91: 2532-2540.
Inaki K., Takahashi Y.K., Nagayama S. & Mori K. Molecular–feature domains with posterodorsal-anteroventral polarity in the symmetrical sensory maps of the mouse olfactory bulb: mapping of odourant-induced Zif268 expression. Eur. J. Neurosci. (2002) 15: 1563-1574.
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