Connectivity, Computation, and Plasticity of the Early Visual System

The visual system is a complex hierarchical structure that processes diverse visual information to guide cognition and behavior. Elucidating the principles that govern the development and function of the visual system's circuitry is a central goal in visual neuroscience. This review examines connectivity, computation, and plasticity within the early mammalian visual system, focusing on three key structures: the retina, the superior colliculus (SC), and the primary visual cortex (V1). The retina serves as the initial site for visual information processing, culminating in activation of highly selective retinal ganglion cells (RGCs), which convey all visual information to the brain. The SC is a primary retinorecipient region that integrates visual information to guide appropriate behavioral responses, exhibiting visual processing both similar to and distinct from RGCs. Retinal information is also relayed via the thalamus to V1, which extracts detailed visual features through spatial and temporal integration, forming the basis of conscious visual perception. The development of these structures involves a coarse-to-fine maturation of functional networks driven by intrinsic mechanisms, including molecular cues and spontaneous patterns of activity. In addition, experience-dependent plasticity in the SC and V1 allows the visual system to adapt to changes of sensory inputs during development. Recent work has significantly advanced our understanding of the complex neuronal computations executed in these early visual regions and the molecular and circuit mechanisms underlying development and plasticity. This knowledge has significant implications for both basic neuroscience and clinical applications, particularly in the context of visual system disorders.