Patchwork-type spontaneous activity in neonatal barrel cortex layer 4 transmitted via thalamocortical projections
Hidenobu Mizuno, Koji Ikezoe, Shingo Nakazawa, Takuya Sato, Kazuo Kitamura, Takuji Iwasato
Cell Reports Volume 22, Issue 1, p123–135, 2 January 2018 DOI:10.1016/j.celrep.2017.12.012
Pressrelease(In Japanese only)
Establishment of precise neuronal connectivity in the mammalian neocortex relies on activity-dependent circuit reorganization during postnatal development; however, the nature of cortical activity during this period remains largely unknown.
Using two-photon calcium imaging of the mouse somatosensory cortex (barrel cortex) in vivo during the first postnatal week, we revealed that layer 4 (L4) cortical neurons within the same barrel fire synchronously in the absence of peripheral stimulation, creating a “patchwork” pattern of spontaneous activity corresponding to the barrel map. By generating transgenic mice expressing a genetically-coded calcium indicator GCaMP6s in thalamocortical axons, we showed that thalamocortical axons also demonstrated the spontaneous patchwork activity pattern. Patchwork activity was diminished by peripheral anesthesia but was mostly independent of self-generated whisker movements. The patchwork activity pattern largely disappeared during postnatal week 2, as even L4 neurons within the same barrel tended to fire asynchronously. This spontaneous L4 activity pattern has features suitable for circuit refinement in the neonatal barrel cortex.
This work was supported by JSPS KAKENHI grant numbers JP15K14322 and JP16H06143, the Takeda Science Foundation, and the Collaborative Research Project (2017-2923) of Brain Research Institute, Niigata University to H.M., and JSPS KAKENHI grant numbers JP16K14559, JP15H01454, and JP15H04263, and Grant-in Scientific Research on Innovation Areas “Dynamic Regulation of Brain Function by Scrap & Build System” (JP16H06459) from MEXT to T.I.