title: Is Fourier analysis performed by the visual system or by the visual investigator.
abstract: A numerical Fourier transform was made of the pincushion grid illusion and the spectral components orthogonal to the illusory lines were isolated. Their inverse transform creates a picture of the illusion. The spatial-frequency response of cortical, simple receptive field neurons similarly filters the grid. A complete set of these neurons thus approximates a two-dimensional Fourier analyzer. One cannot conclude, however, that the brain actually uses frequency-domain information to interpret visual images.
mesh_terms: D000818:Animals; D005583:Fourier Analysis; D000882:Haplorhini; D006801:Humans; D009903:Optical Illusions / Q000502:physiology; D014793:Visual Cortex / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*