the image that remains after a stimulus is removed
Afterimage An afterimage is an image that continues to appear in one's vision after the exposure to the original image has ceased. An afterimage may be a normal phenomenon (physiological afterimage) or may be pathological (palinopsia). Illusory palinopsia may be a pathological exaggeration of physiological afterimages. Afterimages occur because photochemical activity in the retina continues even when you are no longer experiencing the original stimulus.[1][2] The remainder of this article refers to physiological afterimages. A common physiological afterimage is the dim area that seems to float before one's eyes after briefly looking into a light source, such as a camera flash. Afterimages are a common symptom of visual snow.
Receptive field Idealized models of visual receptive fields similar to those found in the retina, lateral geniculate nucleus (LGN) and the primary visual cortex of higher mammals can be derived in an axiomatic way from structural requirements on the first stages of visual processing that reflect symmetry properties of the surrounding world.[7][8] Specifically, functional models for linear receptive fields can be derived in a principled manner to constitute a combination of Gaussian derivatives over the spatial domain and either non-causal Gaussian derivatives or truly time-causal temporal scale-space kernels over the temporal domain. Such receptive fields can be shown to enable computation of invariant visual representations under natural image transformations.[9] By these results, the different shapes of receptive field profiles found in biological vision, which are tuned to different sizes and orientations in the image domain as well as to different image velocities in space-time, can be seen as well adapted to structure of the physical world and be explained from the requirement that the visual system should be invariant to the natural types of image transformations that occur in its environment.[7][8][9]