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In this study, we found that the callosal projection to the contralateral cortex was arrested by unilateral transection of ION or lesion of all whisker follicles before P7. We pursued this further by assessing the effects of non-simultaneous bilateral ION transection. To examine electrophysiological changes of cortical neuron after unilateral or bilateral removal of sensory input, patch-clump recording leii performed in brain slice.
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Simultaneous bilateral ION transection has no effect but non-simultaneous bilateral transection blocks callosal target leu. YQD conceived the study. To follow the outgrowth of callosal axons of somatosensory neurons, we delivered an EGFP expression construct into the pyramidal neurons of the somatosensory cortex by in utero electroporation at Pre-target axon sorting establishes the neural map topography.
Secondary somatosensory cortex; sEPSC: In mice with bilateral removal of sensory input, frequency of sEPSC of the cortical neurons in the S1 is equally reduced on both sides. We next asked whether sensory input to the targeted cortex is also required for the formation of this callosal projection.
Spontaneous excitatory postsynaptic current; VPM: In mouse, the early-born layer V callosal neurons cross the midline before birth, while the late-born layer II-III callosal neurons cross the midline several days after birth [ 3 – 5 ].
Our results not only show the requirement of sensory input in wiring of callosal connection, but also reveal the critical role of balanced bilateral sensory input in this developmental 113344.
All authors read and approved the final manuscript. Surprisingly, simultaneous bilateral transecting IONs did not obviously affect the callosal projection, whereas non-simultaneous bilateral transection also arrested the callosal projection.
Support Center Support Center. Forebrain patterning defects in Small eye mutant mice.
Sensory input is generally thought to be necessary for refining and consolidating neuronal connections during brain development. Ventral posteriomedial thalamic nucleus; Uni. Evidence from mutant mice has shown that guidance molecules, such as Netrin [ 9 ] and Slit [ 10 ], transcription factors, such as Emx1 [ 11 ] and Pax6 [ 12 ], and intracellular molecules, such as P35 and Cdk5 [ 13 ], are involved in the midline crossing of callosal axons.
Results Unilateral transection of ION on either side abolishes callosal projection To follow the outgrowth of callosal axons of somatosensory neurons, we delivered lfi EGFP expression construct into the pyramidal neurons of the somatosensory cortex by in utero electroporation at A-G c-Fos expression was examined in P9 brain slices.
We wondered whether sensory input influences the timing of target zone invasion. Conclusion 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. At least three mice were examined in each group, and neuron numbers for each recoding are indicated. Agenesis of the corpus callosum: By contrast, lesion of all whisker hair follicles on one side at P4 and the other side at P5 did not rescue the projection defect.
National Center for Biotechnology InformationU. Every sixth sections were collected as one set section, in which about three sections were included at the approximate level of Bregma Similar results are obtained by lesion of whisker hair follicles.
This article has been cited by other articles in PMC. Transection at P5, however, does not disrupt barrel formation [ 1617 ], but would be expected to eliminate the later sensory input. While simultaneous bilateral ION transection or lesion of whisker hair follicles did not obviously affect the callosal projection, whereas non-simultaneous bilateral transection of IONs or lesions whisker hair follicles arrested the callosal projection.
Unilateral transection of ION; Uni.
Comparison of numbers of c-Fos-positive neurons is shown in G ; animal numbers examined are indicated. To test this possibility, c-Fos was used to examine cortical neuronal activity in P9 brain slices prepared from mice with P5 unilateral or simultaneous bilateral removal of sensory input. Discussion In this study, we removed somatosensory input by transecting the ION or lesion of whisker hair follicles to examine the effects of sensory input on the development of the corpus callosum.
Published online Dec 5. We here report that cortical callosal axons in somatosensory cortex require sensory input for their target selection in contralateral cortex. Representative recordings in brain slice prepared from mice with ION transection are shown in left panel, and quantification of the sEPSC frequency is shown in right two panels.
How monocular deprivation shifts ocular dominance in visual cortex of young mice. On the basis of these findings, it is likely that during early postnatal development sensory input-driven neuronal activity plays an important role in guiding growing axons to select correct target to establish proper neuronal connections. Electric pulses were then delivered to the embryos by gently clasping their heads with forceps-shaped electrodes connected to a square-pulse generator, ECM BTX; Holliston, MA.
Competing interests The authors declare that they have no competing interests. However, it should be noted that our neurophysiological results are not sufficient to establish a causal link between the mismatched neuronal activity and defective callosal projection, and further studies are needed to explore this question.
These findings promote us to examine whether sensory input is required for the formation of callosal connection in the somatosensory cortex. Activity-dependent development of callosal projections in the somatosensory cortex. In this study, we removed somatosensory input by transecting the ION or lesion of whisker hair follicles to examine the effects of sensory input on the development of the corpus callosum.
Sensory input is required for callosal axon targeting in the somatosensory cortex
Mice lacking p35, a neuronal specific activator of Cdk5, display cortical lamination defects, seizures, and adult lethality. Four-thirteen neurons were recorded in each group, and data were stored with a personal computer using software of pCLAMP 10 and analyzed with Mini Analysis Synaptosoft Inc.
Callosal projections in rat somatosensory cortex are altered by early removal of afferent input. For example, spontaneous rhythmic activity in early chick spinal cord influences distinct motor axon pathfinding decisions [ 26 ], and intraventricular injection of tetrodotoxin blocks cortical target selection of thalamocortical axons [ 27 ]. A case of schizophrenia with complete agenesis of the corpus callosum. Callosal projection is affected by unilateral but rescued by bilateral lesion of whisker hair follicles.
Evidence for activity-dependent cortical wiring: Journal List Mol Brain v. In contrast, unilateral lesion of the optic tract, which eliminates all visual input to one hemisphere, results in a nearly complete absence of callosal connections in the border region between the primary and secondary visual cortices [ 19 ].