Figure 8. A Model for Chandelier Cell Elimination and Visual System Development.

(A) In rodents, information in the central visual field is first projected separately to the temporal region of the left and right retina, relayed largely in parallel through the lateral geniculate nuclei (LGN), and converge at the lateral region of the primary visual cortex (V1), defining the binocular zone (BZ). In addition to this convergence of ipsi- and contralateral LGN-V1 inputs, pyramidal neurons at BZ project to the contralateral BZ, forming a transcallosal pathway that also contributes to binocular response properties (defined as callosal binocular zone, cBZ, shown in green).

(B) Chandelier cell elimination takes place between P7 to P14 before eye opening. The timing coincides with axonal projections of transcallosal neurons onto the contralateral hemisphere as well as spontaneous retinal activity before eye opening (Huberman et al., 2008).

(C) At P7, abundance of ChCs at the cBZ may form promiscuous connectivity between ChCs and callosal projecting neurons. As GABAergic transmission may be depolarizing at early postnatal ages, ChCs innervating callosal PyNs might promote their firing, forming a transcallosal loop, which is further driven by coordinated bilateral retinal inputs. Such a transient over-excited network may drive the elimination of “mis-wired” ChCs through apoptosis, resulting a reduction in ChCs by P14.