Abstract
In order to determine how shape perception is constructed in our brain, we need first to establish what the most fundamental building blocks are. Edges are often considered the most basic features in the visual world, and neurons in the early visual system are often referred to as “edge detectors”. However, some works of art by Victor Vasarely show that junctions can be more salient, perceptually, than edges, even when the physical luminance change is equivalent. To examine the underlying physiology, we presented Vasarely's illusions (and some novel effects based on them) to awake monkeys while recording eye movements and neural activity from single neurons in the LGN and area V1. Our results show that junctions do in fact generate stronger visual responses than edges in the early visual system. These data furthermore represent the first physiological correlates of Vasarely's effect, and may have broad implications for the processing of shape perception at its earliest stages.