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Afterimage
An afterimage, or after-image, is an image that continues to appear in the eyes after a period of exposure to the original image. 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 Photochemistry, photochemical activity in the retina continues even when the eyes are no longer experiencing the original stimulus. The remainder of this article refers to physiological afterimages. A common physiological afterimage is the dim area that seems to float before one's human eye, eyes after briefly looking into a light source, such as a camera flash. Palinopsia is a common symptom of visual snow. Negative afterimages Negative image, Negative afterimages are generated in the retina but may be modified like other retinal signals by neural adaptation of the retinal ganglion cells that carry signals from the retina of the eye to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Palinopsia
Palinopsia (Greek: ''palin'' for "again" and ''opsia'' for "seeing") is the persistent recurrence of a visual image after the stimulus (psychology), stimulus has been removed. Palinopsia is not a diagnosis; it is a diverse group of pathology, pathological visual symptoms with a wide variety of causes. Visual perseveration is Synonym, synonymous with palinopsia. In 2014, Gersztenkorn and Lee comprehensively reviewed all cases of palinopsia in the literature and subdivided it into two clinically relevant groups: illusory palinopsia and hallucinatory palinopsia. Hallucinatory palinopsia, usually due to seizures or visual pathway#Biology of the visual system, posterior cerebral cortex, cortical lesions, describes afterimages that are formed, long-lasting, and high resolution. Illusory palinopsia, usually due to migraines, closed head injury, head trauma, prescription drugs, visual snow syndrome or hallucinogen persisting perception disorder (HPPD), describes afterimages that are affecte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Illusory Palinopsia
Illusory palinopsia is a subtype of palinopsia, a visual disturbance defined as the persistence or recurrence of a visual image after the stimulus has been removed. Palinopsia is a broad term describing a heterogeneous group of symptoms, which is divided into hallucinatory palinopsia and illusory palinopsia. Illusory palinopsia is likely due to sustained awareness of a stimulus and is similar to a visual illusion: the distorted perception of a real external stimulus. Illusory palinopsia is caused by migraines, hallucinogen persisting perception disorder (HPPD), prescription drugs, and head trauma, but is also sometimes idiopathic. Illusory palinopsia consists of afterimages that are short-lived or unformed, occur at the same location in the visual field as the original stimulus, and are often exposed or exacerbated based on environmental parameters such as stimulus intensity, background contrast, fixation, and movement. Illusory palinopsia symptoms occur continuously or predi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Opponent Process
The opponent process is a color theory that states that the human visual system interprets information about color by processing signals from photoreceptor cells in an antagonistic manner. The opponent-process theory suggests that there are three opponent channels, each comprising an opposing color pair: red versus green, blue versus yellow, and black versus white (luminance). The theory was first proposed in 1892 by the German physiologist Ewald Hering. Color theory Complementary colors When staring at a bright color for a while (e.g. red), then looking away at a white field, an afterimage An afterimage, or after-image, is an image that continues to appear in the eyes after a period of exposure to the original image. An afterimage may be a normal phenomenon (physiological afterimage) or may be pathological (palinopsia). Illusory ... is perceived, such that the original color will evoke its complementary color (green, in the case of red input). When complementary colors ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Complementary Color
Complementary colors are pairs of colors which, when combined or color mixing, mixed, cancel each other out (lose Colorfulness, chroma) by producing a grayscale color like white or black. When placed next to each other, they create the strongest contrast (vision), contrast for those two colors. Complementary colors may also be called "opposite colors". Which pairs of colors are considered complementary depends on the color model that one uses: * Modern color theory uses either the RGB color model, RGB additive color model or the CMYK color model, CMY subtractive color model, and in these, the complementary pairs are red–cyan, green–magenta (one of the purples), and blue–yellow. * In the traditional RYB color model, the complementary color pairs are red–green, yellow–purple, and blue–orange (colour), orange. * Opponent process theory suggests that the most contrasting color pairs are red–green and blue–yellow. * The black–white color pair is common to all the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Motion Aftereffect
The motion aftereffect (MAE) is a visual illusion experienced after viewing a moving visual stimulus for a time (tens of milliseconds to minutes) with stationary eyes, and then fixating a stationary stimulus. The stationary stimulus appears to move in the opposite direction to the original (physically moving) stimulus. The motion aftereffect is believed to be the result of motion adaptation. For example, if one looks at a waterfall for about a minute and then looks at the stationary rocks at the side of the waterfall, these rocks appear to be moving upwards slightly. The illusory upwards movement is the motion aftereffect. This particular motion aftereffect is also known as the ''waterfall illusion''. Another example can be seen when one looks at the center of a rotating spiral for several seconds. The spiral can exhibit outward or inward motion. When one then looks at any stationary pattern, it appears to be moving in the opposite direction. This form of the motion aftereffect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Book Of Optics
The ''Book of Optics'' (; or ''Perspectiva''; ) is a seven-volume treatise on optics and other fields of study composed by the medieval Arab scholar Ibn al-Haytham, known in the West as Alhazen or Alhacen (965–c. 1040 AD). The ''Book of Optics'' presented experimentally founded arguments against the widely held extramission theory of vision (as held by Euclid in his ''Optica''), and proposed the modern intromission theory, the now accepted model that vision takes place by light entering the eye.D. C. Lindberg (1976), ''Theories of Vision from al-Kindi to Kepler'', Chicago, Univ. of Chicago Press The book is also noted for its early use of the scientific method, its description of the camera obscura, and its formulation of Alhazen's problem. The book extensively affected the development of optics, physics and mathematics in Europe between the 13th and 17th centuries. Vision theory Before the ''Book of Optics'' was written, two theories of vision existed. The extra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Emmert's Law
Emmert's law states that objects that generate retinal images of the same size will look different in physical size (linear size) if they appear to be located at different distances. Specifically, the ''perceived linear size'' of an object increases as its ''perceived'' distance from the observer increases. This makes intuitive sense: an object of constant size will project progressively smaller retinal images as its distance from the observer increases. Similarly, if the retinal images of two ''different'' objects at different distances are the same, the physical size of the object that is farther away must be larger than the one that is closer. Creation and purpose Emil Emmert (1844–1911) first described the law in 1881. He noted that an afterimage appeared to increase in size when projected to a greater distance. Some authors thus take Emmert's law to refer strictly to the increase in the apparent size of an after-image when the distance between observer and projection plane is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visual Cortex
The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and then reaches the visual cortex. The area of the visual cortex that receives the sensory input from the lateral geniculate nucleus is the primary visual cortex, also known as visual area 1 ( V1), Brodmann area 17, or the striate cortex. The extrastriate areas consist of visual areas 2, 3, 4, and 5 (also known as V2, V3, V4, and V5, or Brodmann area 18 and all Brodmann area 19). Both hemispheres of the brain include a visual cortex; the visual cortex in the left hemisphere receives signals from the right visual field, and the visual cortex in the right hemisphere receives signals from the left visual field. Introduction The primary visual cortex (V1) is located in and around the calcarine fissure in the occipital lobe. Each h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flag Of The United States
The national flag of the United States, often referred to as the American flag or the U.S. flag, consists of thirteen horizontal Bar (heraldry), stripes, Variation of the field, alternating red and white, with a blue rectangle in the Canton (flag), canton bearing fifty small, white, five-pointed stars arranged in nine offset horizontal rows, where rows of six stars alternate with rows of five stars. The 50 stars on the flag represent the 50 U.S. states, and the 13 stripes represent the Thirteen Colonies, thirteen British colonies that won independence from Kingdom of Great Britain, Great Britain in the American Revolutionary War. The flag was created as an item of military equipment to identify US ships and forts. It evolved gradually during early American history, and was not designed by any one person. The flag exploded in popularity in 1861 as a symbol of opposition to the Confederate States of America, Confederate Battle of Fort Sumter, attack on Fort Sumter. It came to sy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perceived
Perception () is the organization, identification, and interpretation of sense, sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous system, which in turn result from physical or chemical stimulation of the Sensory nervous system, sensory system.Goldstein (2009) pp. 5–7 Visual system, Vision involves light striking the retina of the eye; Sense of smell, smell is mediated by Olfactory system#Peripheral, odor molecules; and hearing involves Sound wave, pressure waves. Perception is not only the passive receipt of these Signal processing, signals, but it is also shaped by the recipient's Perceptual learning, learning, memory, Expectation (epistemic), expectation, and attention.Richard Gregory, Gregory, Richard. "Perception" in Gregory, Zangwill (1987) pp. 598–601. Sensory input is a process that transforms this low-level information to higher-level information (e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Contrast Effect
A contrast effect is the enhancement or diminishment, relative to normal, of perception, cognition or related performance as a result of successive (immediately previous) or simultaneous exposure to a stimulus of lesser or greater value in the same dimension. (Here, normal perception, cognition or performance is that which would be obtained in the absence of the comparison stimulus—i.e., one based on all previous experience.) Perception example: A neutral gray target will appear lighter or darker than it does in isolation when immediately preceded by, or simultaneously compared to, respectively, a dark gray or light gray target. Cognition example: A person will appear more or less attractive than that person does in isolation when immediately preceded by, or simultaneously compared to, respectively, a less or more attractive person. Performance example: A laboratory rat will work faster, or slower, during a stimulus predicting a given amount of reward when that stimulus and r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
