The ability to adjust to changing conditions is critical to the functioning of any sensory system. The vertebrate visual system, for example, is well-known for its flexibility - as an animal moves between different environments, the visual system adjusts its processing to match the changing conditions. Though these adjustments have been recognized for years, the mechanisms that underlie them have been unclear. Here we describe a case in which the mechanism could be determined. We investigate a well-known set of adjustments - the adjustments in spatial and temporal processing that accompany the shift from day to night vision. Our findings reveal a novel mechanism in the retina that underlies the adjustment of temporal processing, which may generalize to other networks as well. Further, characterizing these adjustments reveals a previously unknown divergence in the retina's parallel pathways, one that has functional relevance to natural vision.