Decoupling eye-specific segregation from lamination in the lateral geniculate nucleus.

To determine whether there is a critical period for development of eye-specific layers in the lateral geniculate nucleus (LGN), we prevented the normal segregation of retinogeniculate afferents and then allowed an extended period of time for recovery. After recovery, both anatomy and physiology revealed strictly nonoverlapping territories of input from the two eyes. However, the normal stereotyped pattern of eye-specific afferent and cellular layers never developed. Instead, the eye-specific territories of afferent input emerged as variable and disorganized patches with no corresponding interlaminar spaces in the LGN. These findings reveal a critical period for coordinating the development of three processes in the LGN: the segregation of afferents from the two eyes, the spatial organization of those afferents into layers, and the alignment of postsynaptic cytoarchitecture with the afferent inputs. We also assessed the physiological consequences of preventing normal lamination and found normal single-cell responses and topographic representation of visual space in the LGN. Clusters of ON-center and OFF-center LGN cells were segregated from one another as in normal animals. However, the organization of ON and OFF sublaminas in the treated animals was disrupted.