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Insights into Synaptic Input Organization in the Visual Cortex of Mouse Through In Vivo Recordings

This journal club introduces a study examining how neurons in the visual cortex process synaptic inputs to generate firing patterns. The researchers used advanced imaging techniques to identify specific features of dendritic synapses and their relationship to neuron output. Results highlight the importance of distributed inputs in neuronal integration. A progress report on injecting Lidocaine into the MGB nucleus and its effect on neuronal firing patterns is also discussed.

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Insights into Synaptic Input Organization in the Visual Cortex of Mouse Through In Vivo Recordings

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  1. Journal Club Yu Kai 2010/09/27

  2. Introduction In sensory cortical areas, neurons are turned to specific stimulus features. In the present paper, the authers investigate the characteristics of the synaptic input that cortical neurons receive to generate their output firing pattern in the visual cortex of mouse.

  3. The mechanism by which neurons generate signals: Inputin dendriticsynapase Integration in neuron soma Outputas spikes

  4. Isolation of input from neuron in vivo They use the approach combining high-speed two-photon imaging with whole-cell patch recordings to identify local sub-threshold calcium signals that correspond to orientation-specific synaptic inputs

  5. Isolation of input from neuron in vivo Whole-cell current-clamp recordings of responses to drifting gratings of different orientations. Three trials were superimposed.

  6. Isolation of input from neuron in vivo:Calcium transient in distal dendrites

  7. Isolation of input from neuron in vivo:Calcium recordings from five neighbouringdendritic regions

  8. Isolation of input from neuron in vivo:Exclusive the dendritic NMDA spike

  9. Results: Visually evoked action potentials, subthresholddepolarizations

  10. Results:Distribution of dendritic hotspots (red dots) to the prefered orientation stimuli

  11. Results: Orientation perfermance different in the same dentrite

  12. Conclusion: The results reveal basic insights into the dendritic organization of sensory inputs to neurons of the visual cortex in vivo. • Identified discrete dendritic hotspots as synaptic entry sites for specific sensory features • Afferent sensory inputs with the same orientation preference are widely dispersed over thedendritic tree and do not converge on single dendrites • Neurons with a highly tuned output signal receive input signals that are heterogeneous The results support a neuronal integration model involving summation of distributed inputs, rather than models that stress the role of convergent inputs to single dendrites.

  13. Progress Report

  14. Verify responsibilities of MGB locus which very close to the injection position

  15. InjetionLidocaine into the MGB while continuous recording in A1 Lidocaine Injection Raster Plot indicate the lidocaine injection cause inversible change on the firing pattern of responses to acoustic stimulation.

  16. Corresponding recording before lidocaine injection

  17. After

  18. Intracellular Recording of cortical neuron in layer2/3 Before lidocaine into MGB

  19. After

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