title: Sensory input is required for callosal axon targeting in the somatosensory cortex.
abstract: BACKGROUND
  Sensory input is generally thought to be necessary for refining and consolidating neuronal connections during brain development. We here report that cortical callosal axons in somatosensory cortex require sensory input for their target selection in contralateral cortex.
  
  
  RESULTS
  Eliminating sensory input to either hemisphere by unilateral transection of infraorbital nerve (ION) prevents target selection of callosal axons in contralateral cortex. Strikingly, blocking sensory input bilaterally, by simultaneously transecting both IONs, results in rescued callosal projection. In contrast, non-simultaneous bilateral ION transection has the same effect as unilateral transection. Similar results are obtained by lesion of whisker hair follicles. c-Fos-positive neurons in brain slices treated with KCl is decreased more in contralateral cortex with unilateral removal of sensory input, but decreased similarly in both cortices in mice with simultaneous bilateral removal of sensory input. Frequency of sEPSC of cortical neurons is also reduced in contralateral cortex with the unilateral removal of sensory input, but equally reduced on both sides with the bilateral removal of sensory input, suggesting that unbalanced bilateral sensory input might lead to mismatched neuronal activity between the two cortices and contribute to the formation of callosal projection.
  
  
  CONCLUSIONS
  Our data demonstrate a critical role of balanced bilateral somatosensory input in the formation of callosal connections, and thus reveal a new role of sensory input in wiring brain circuits.
authors.affiliation: Key Laboratory of Arrhythmias, Ministry of Education, East Hospitial, Tongji University School of Medicine, 1239 Siping Road, Shanghai, 200092, China. dingyuqiang@gmail.com.
authors.forename: Ying
authors.initials: Y
authors.lastname: Huang
authors.forename: Ning-Ning
authors.initials: NN
authors.lastname: Song
authors.forename: Wei
authors.initials: W
authors.lastname: Lan
authors.forename: Qiong
authors.initials: Q
authors.lastname: Zhang
authors.forename: Ling
authors.initials: L
authors.lastname: Zhang
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Ling
authors.initials: L
authors.lastname: Hu
authors.forename: Jia-Yin
authors.initials: JY
authors.lastname: Chen
authors.forename: Chun-Jie
authors.initials: CJ
authors.lastname: Zhao
authors.forename: Lingjiang
authors.initials: L
authors.lastname: Li
authors.forename: Lin
authors.initials: L
authors.lastname: Xu
authors.forename: Yu-Qiang
authors.initials: YQ
authors.lastname: Ding
mesh_terms: D000818:Animals; D001369:Axons / Q000473:pathology*; D003337:Corpus Callosum / Q000473:pathology / Q000503:physiopathology*; D018859:Hair Follicle / Q000294:innervation; D051379:Mice; D008810:Mice, Inbred C57BL; D009915:Orbit / Q000293:injuries / Q000294:innervation; D010641:Phenotype; D012677:Sensation; D013003:Somatosensory Cortex / Q000473:pathology / Q000503:physiopathology*; D014738:Vibrissae / Q000294:innervation