DEVELOPMENTAL NEUROPHYSIOLOGY

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Molecular & Developmental Biology (Yoshimura Group)

Yoshimura GrouopHigashijima Grouop(←CLICK)
Yumiko Yoshimura(Prof.)
Shin-ichi Higashijima(Assoc. Prof.)
Takuma Mori(Assis. Prof.)

RESEARCH THEMES

The aim of our group is to clarify the neuronal circuit underling information processing in neocortex. To this purpose, we have been conducting electrophysiological studies using slice preparations and anesthetized intact animals. Primary visual cortex is one of the best areas to study the relationship between brain functions and synapses/neural circuits, because the visual responsiveness of each neuron and the functional columnar structures are well characterized in this area. Therefore, we have analyzed the synapses and neuronal circuits in this cortical area, and clarified their basic properties. For example, we tested for fine-scale specificity of connections in rat visual cortex using cross-correlation analyses of synaptic currents evoked by laser scanning photostimulation. Recording simultaneously from adjacent layer 2/3 pyramidal cells, we found that when the cells were connected they shared inputs from individual excitatory neurons in layer 4 and layer 2/3. Thus, excitatory connections from layer 4 to layer 2/3 and within layer 2/3 form fine-scale assemblies of selectively interconnected neurons. To characterize connection properties further and elucidate the role of the fine-scale circuit in visual information processing, we are currently conducting electrophysiological analyses of neural circuits using slice preparations prepared from transgenic mice in which cells responding to particular visual stimulation can be visualized by fluorescent proteins expressed in an activity-dependent manner. Another important subject of our research is the activity-dependent developmental of visual responsiveness and neuronal circuits. It is known that visual function matures under the strong influence of postnatal experience. We have been examining the effect of manipulation of visual inputs on the development of synaptic connections and neuronal circuits, to unravel the synaptic mechanisms of activity-dependent maturation of cortical functions.

Schematic diagram illustrating the fine-scale organization of cortical connections

 

SELECTED PUBLICATIONS

  1. Y. Yoshimura, M. Inaba, K. Yamada, T. Kurotani, T. Begum, F. Reza, T. Maruyama & Y. Komatsu: "Involvement of T-type Ca2+ channels in the potentiation of synaptic and visual responses during the critical period in rat visual cortex." European Journal of Neuroscience, 28, 730-743 (2008)
  2. T. Kurotani, K. Yamada, Y. Yoshimura, M. C. Crair & Y. Komatsu: "State-dependent bidirectional modification of somatic inhibition in neocortical pyramidal cells." Neuron 57, 905-916 (2008)
  3. M. Ren, Y. Yoshimura, N. Takada, S. Horibe & Y. Komatsu: "Specialized inhibitory synaptic actions between nearby neocortical pyramidal neurons." Science 316 (758): 758-761 (2007)
  4. Y. Yoshimrua, J. L.M. Danzker & E. M. Callaway: "Excitatory cortical neurons form fine-scale functional networks." Nature 433, 868-873 (2005)
  5. Y. Yoshimura & E. M. Callaway: "Fine-scale specificity of cortical networks depends on inhibitory cell type and connectivity." Nature Neuroscience 8(11): 1552-1559, 2005