![]() First-order motion perceptionįirst-order motion perception refers to the perception of the motion of an object that differs in luminance from its background, such as a black bug crawling across a white page. MOTION PARALLAX PSYCHOLOGY DEFINITION SERIESNeuropsychological studies of a patient who could not see motion, seeing the world in a series of static "frames" instead, suggested that visual area V5 in the human is homologous to area MT in the primate. 8.1 Labs specialising in motion researchĪrea V5 seems to be important to the processing of visual motion and damage to this area can disrupt motion perception.This appears to occur in Area MT/V5 in human visual cortex. Because each neuron will suffer from the aperture problem the estimates from many neurons are then integrated into a global motion estimate. Individual neurons initially estimate motion locally within their receptive field. In the second figure the visual input and prior assumptions together make it appear the stripes are moving to the bottom-right. In cases where motion cannot be determined based on visual input alone, the visual system is thought to rely on prior assumptions. The motion direction of a straight line is fundamentally ambiguous, because the motion component parallel to the line cannot be inferred based on the visual input. At the resolution of this apperture visual cues can often be approximated by straight lines. Each neuron in the visual system is sensitive to visual input in a small part of our visual field, as if each neuron is looking at the visual input through a small apperture. In addition to the problems of motion perception mentioned above, a number of issues arise due to the physiology of the brain. In reality the motion is identical in both figures. Though the motion of the barberpole in the top figure appears to be downward, the motion appears to be both downward and rightward when viewed through an aperture in the bottom figure. It will only 'see' part of the barberpole shown above. A neuron in visual cortex has a limited receptive field. However, the actual motion is a rotation of the barberpole around its longer axis, which should have created a rightward motion. The stripes on the pole appear to move downward along the pole's longer axis. When a diagonally-striped pole is rotated around its longer axis, so that the stripes are moving in the direction of the pole's shorter axis, it nonetheless appears the stripes are moving in the direction of its longer axis. A well known example is the barberpole illusion. These issues become more apparent when we look at visual illusions involving motion. The problem of motion estimation generalizes to binocular vision when we consider occlusion or motion perception at relatively large distances, where binocular disparity is a poor cue to depth. Put differently, many 3D scenes will be compatible with a single 2D projection. The motion cues present in the 2D projection will by default be insufficient to reconstruct the motion present in the 3D scene. In monocular vision for example, the visual input will be a 2D projection of a 3D scene. The observer's visual input is generally insufficient to uniquely determine the 'true' velocity in a visual scene. Although this process appears straightforward to most observers, it has proven to be a difficult problem from a computational perspective, and extraordinarily difficult to explain in terms of neural processing. Motion perception is an aspect of spatial perception and is the process of inferring the speed and direction of elements in a scene based on visual input. The dorsal stream is responsible for detection of location and motion.įor the perception of ones own motion see: proprioception They originate from a common source in visual cortex. The dorsal stream (green) and ventral stream (purple) are shown. This banner appears on articles that are weak and whose contents should be approached with academic caution. Please help recruit one, or improve this page yourself if you are qualified. This article is in need of attention from a psychologist/academic expert on the subject. ![]()
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