Dendritic growth

Introduction Retinal neuron arbors are organized in relation to three central functions. (1) Outgrowth is regulated in the lateral dimension to delimit receptive-field size, a property linked to spatial acuity. (2) Interactions between individual neuronal subtypes are coordinated with respect to neuritic overlap to promote complete coverage, or tiling, of the retina, thus assuring that distinct functions have representation over the entire area of the retina (see Chapter 10). (3) Interactions between pre- and postsynaptic partners are organized in the vertical dimension such that functionally discrete circuits are physically isolated within the synaptic neuropil. For instance, during development of the inner plexiform layer (IPL) connections between subsets of bipolar, amacrine and retinal ganglion cells come to be arranged in a laminar fashion, sometimes occupying single strata within a multilayered array of concentric circuits (Figure 12.1). In this chapter the current state of understanding regarding the structural development of retinal neuron arbors is discussed: from mechanisms that impact individual neuronal morphologies to those that orchestrate interactions between synaptic partners. In the first section, issues concerning initial neurite extension are discussed. These include establishing cellular polarity and compartmentalization of neurites into the axon and dendrites. Section two focuses on the establishment of dendritic territory and interactions that influence receptive-field size. The last section deals with the process of sublamination, whereby individual neuritic arbors resolve into monostratified, multistratified, or diffuse (non-stratified) configurations within the IPL.