Uncovering Potential Effects of Spontaneous Waves on Synaptic Development: The Visual System as a Model

Spontaneous waves are ubiquitous during early brain development and are hypothesized to drive the development of receptive fields (RFs). Different stages of retinal waves, characterized by activity patterns in the retina and downstream areas, coincide with key developments along the visual pathway. Stage II waves, in particular, have been linked to a possible early synaptic pruning process; however, the mechanisms underlying their activity-dependent effects on thalamocortical synapses remain poorly understood. In this work, we develop a biologically constrained model of thalamocortical synapse formation driven by stage II retinal waves. Using this, alongside a reduced rate-based model, we propose mechanisms underlying the formation of distinct RF structures, including transitions from a disklike RF to a ringlike RF, modulated by learning parameters and initial synaptic connection strengths. We leverage the mechanisms uncovered through the reduced model to make two predictions: gap junctions promote local retinotopic refinement during stage II waves, and the resulting RF structure established during this stage controls the emergence of orientation selectivity later in development. Mechanisms identified here may aid in the understanding of developing synaptic structures across various cortical regions.