Adaptation is ubiquitous in sensory perception. While the perceptual consequences of adaptation have been widely studied and characterized as various forms of aftereffects, the functional and neural mechanism underlying adaptation are less clear. I will present some recent work that looked at the relationship between the physiological and perceptual changes induced by adaptation. Assuming an encoding-decoding cascade model for perception, I will show that for many different perceptual modalities adaptation is best explained as a mechanism that changes the encoding of perceptual information while decoding is essentially unaware of these changes. The resulting aftereffect provides a general perceptual signature of adaptation. For the specific case of visual motion perception, I will demonstrate that motion aftereffects reflect a superposition of two of such signatures, providing a unifying explanation for the diversity of motion aftereffects. This suggests that adaptation is governed by an isomorphic mechanism acting simultaneously at several stages along the perceptual processing hierarchy.