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Filling-in
In vision, filling-in phenomena are those responsible for the completion of missing information across the physiological blind spot, and across natural and artificial scotomata. There is also evidence for similar mechanisms of completion in normal visual analysis. Classical demonstrations of perceptual filling-in involve filling in at the blind spot in monocular vision, and images stabilized on the retina either by means of special lenses, or under certain conditions of steady fixation. For example, naturally in monocular vision at the physiological blind spot, the percept is not a hole in the visual field, but the content is “filled-in” based on information from the surrounding visual field. When a textured stimulus is presented centered on but extending beyond the region of the blind spot, a continuous texture is perceived. This partially inferred percept is paradoxically considered more reliable than a percept based on external input. (Ehinger ''et al.'' 2017). A second ty ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blind Spot (vision)
A blind spot, scotoma, is an obscuration of the visual field. A particular blind spot known as the ''physiological blind spot'', "blind point", or ''punctum caecum'' in medical literature, is the place in the visual field that corresponds to the lack of light-detecting photoreceptor cells on the optic disc of the retina where the optic nerve passes through the optic disc.Gregory, R., & Cavanagh, P. (2011)"The Blind Spot" Scholarpedia. Retrieved on 2011-05-21. Because there are no cells to detect light on the optic disc, the corresponding part of the field of vision is invisible. Processes in the brain interpolate the blind spot based on surrounding detail and information from the other eye, so it is not normally perceived. Although all vertebrates have this blind spot, cephalopod eyes, which are only superficially similar, do not. In them, the optic nerve approaches the receptors from behind, so it does not create a break in the retina. The first documented observation of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Illusory Contours
Illusory contours or subjective contours are visual illusions that evoke the perception of an edge without a luminance or color change across that edge. Illusory brightness and depth ordering often accompany illusory contours. Friedrich Schumann is often credited with the discovery of illusory contours around the beginning of the 20th century, but they are present in art dating to the Middle Ages. Gaetano Kanizsa’s 1976 ''Scientific American'' paper marked the resurgence of interest in illusory contours for vision scientists. Common types of illusory contours Kanizsa figures Perhaps the most famous example of an illusory contour is the Pac-Man configuration popularized by Gaetano Kanizsa. Kanizsa figures trigger the percept of an illusory contour by aligning Pac-Man-shaped inducers in the visual field such that the edges form a shape. Although not explicitly part of the image, Kanizsa figures evoke the percept of a shape, defined by a sharp illusory contour. Typically, the sh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Troxler Fading , a phenomenon of visual perception
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Troxler is a surname. Notable people with the surname include: *Ignaz Paul Vital Troxler (1780–1866), Swiss philosopher *Steve Troxler (born 1952), American farmer and politician *Niklaus Troxler, Swiss graphic designer *William 'Beta Ray Billy' Troxler, Dirt Cop who had a short-lived modeling career See also *Troxler's fading Troxler's fading, also called Troxler fading or the Troxler effect, is an optical illusion affecting visual perception. When one fixates on a particular point for even a short period of time, an unchanging stimulus away from the fixation point wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Illusions
Within visual perception, an optical illusion (also called a visual illusion) is an illusion caused by the visual system and characterized by a visual percept that arguably appears to differ from reality. Illusions come in a wide variety; their categorization is difficult because the underlying cause is often not clear but a classification proposed by Richard Gregory is useful as an orientation. According to that, there are three main classes: physical, physiological, and cognitive illusions, and in each class there are four kinds: Ambiguities, distortions, paradoxes, and fictions. A classical example for a physical distortion would be the apparent bending of a stick half immerged in water; an example for a physiological paradox is the motion aftereffect (where, despite movement, position remains unchanged). An example for a physiological fiction is an afterimage. Three typical cognitive distortions are the Ponzo, Poggendorff, and Müller-Lyer illusion. Physical illusions are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tom N
Tom or TOM may refer to: * Tom (given name), a diminutive of Thomas or Tomás or an independent Aramaic given name (and a list of people with the name) Characters * Tom Anderson, a character in '' Beavis and Butt-Head'' * Tom Beck, a character in the 1998 American science-fiction disaster movie '' Deep Impact'' * Tom Buchanan, the main antagonist from the 1925 novel ''The Great Gatsby'' * Tom Cat, a character from the ''Tom and Jerry'' cartoons * Tom Lucitor, a character from the American animated series '' Star vs. the Forces of Evil'' * Tom Natsworthy, from the science fantasy novel '' Mortal Engines'' * Tom Nook, a character in ''Animal Crossing'' video game series * Tom Servo, a robot character from the ''Mystery Science Theater 3000'' television series * Tom Sloane, a non-adult character from the animated sitcom ''Daria'' * Talking Tom, the protagonist from the ''Talking Tom & Friends'' franchise * Tom, a character from the '' Deltora Quest'' books by Emily Rodda * Tom, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Craik–O'Brien–Cornsweet Illusion
The Cornsweet illusion, also known as the Craik–O'Brien–Cornsweet illusion or the Craik–Cornsweet illusion, is an optical illusion that was described in detail by Tom Cornsweet in the late 1960s. Kenneth Craik and Vivian O'Brien had made earlier observations in a similar vein. The original version of the illusion involved a rapidly spinning black-and-white disk, painted in a way that would create the appearance of a gradient effect when in motion. An equivalent static version of illusion is composed of a gray rectangle where the left half fades to a lighter shade as it approaches a vertical center line, and the right half fades to a darker gray approaching the same line. As a result, the whole left half of the rectangle appears lighter than the right half, but in fact the brightness of both areas is exactly the same. This can be seen by blacking out the region containing the edge. This phenomenon is similar to the phenomenon of simultaneous contrast and Mach bands Mac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FMRI
Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the brain is in use, blood flow to that region also increases. The primary form of fMRI uses the blood-oxygen-level dependent (BOLD) contrast, discovered by Seiji Ogawa in 1990. This is a type of specialized brain and body scan used to map neural activity in the brain or spinal cord of humans or other animals by imaging the change in blood flow (hemodynamic response) related to energy use by brain cells. Since the early 1990s, fMRI has come to dominate brain mapping research because it does not involve the use of injections, surgery, the ingestion of substances, or exposure to ionizing radiation. This measure is frequently corrupted by noise from various sources; hence, statistical procedures are used to extract the underlying signal. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homunculus
A homunculus ( , , ; "little person") is a representation of a small human being, originally depicted as small statues made out of clay. Popularized in sixteenth-century alchemy and nineteenth-century fiction, it has historically referred to the creation of a miniature, fully formed human. The concept has roots in preformationism as well as earlier folklore and alchemic traditions. The term lends its name to the cortical homunculus, an image of a person with the size of the body parts distorted to represent how much area of the cerebral cortex of the brain is devoted to it. History Alchemy The homunculus first appears by name in alchemical writings attributed to Paracelsus (1493–1541). ''De natura rerum'' (1537) outlines his method for creating homunculi: Comparisons have been made with several similar concepts in the writings of earlier alchemists. Although the actual word "homunculus" was never used, Carl Jung believed that the concept first appeared in the ''Visions of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Receptive Field
The receptive field, or sensory space, is a delimited medium where some physiological stimuli can evoke a sensory neuronal response in specific organisms. Complexity of the receptive field ranges from the unidimensional chemical structure of odorants to the multidimensional spacetime of human visual field, through the bidimensional skin surface, being a receptive field for touch perception. Receptive fields can positively or negatively alter the membrane potential with or without affecting the rate of action potentials. A sensory space can be dependent of an animal's location. For a particular sound wave traveling in an appropriate transmission medium, by means of sound localization, an auditory space would amount to a reference system that continuously shifts as the animal moves (taking into consideration the space inside the ears as well). Conversely, receptive fields can be largely independent of the animal's location, as in the case of place cells. A sensory space can also m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinal Ganglion Cell
A retinal ganglion cell (RGC) is a type of neuron located near the inner surface (the ganglion cell layer) of the retina of the human eye, eye. It receives visual information from photoreceptor cell, photoreceptors via two intermediate neuron types: Bipolar cell of the retina, bipolar cells and retina amacrine cells. Retina amacrine cells, particularly narrow field cells, are important for creating functional subunits within the ganglion cell layer and making it so that ganglion cells can observe a small dot moving a small distance. Retinal ganglion cells collectively transmit image-forming and non-image forming visual information from the retina in the form of action potential to several regions in the thalamus, hypothalamus, and mesencephalon, or midbrain. Retinal ganglion cells vary significantly in terms of their size, connections, and responses to visual stimulation but they all share the defining property of having a long axon that extends into the brain. These axons form th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Primary 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 hemisphere's V1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amodal Perception
Amodal perception is the perception of the whole of a physical structure when only parts of it affect the sensory receptors. For example, a table will be perceived as a complete volumetric structure even if only part of it—the facing surface—projects to the retina; it is perceived as possessing internal volume and hidden rear surfaces despite the fact that only the near surfaces are exposed to view. Similarly, the world around us is perceived as a surrounding plenum, even though only part of it is in view at any time. Another much quoted example is that of the "dog behind a picket fence" in which a long narrow object (the dog) is partially occluded by fence-posts in front of it, but is nevertheless perceived as a single continuous object. Albert Bregman noted an auditory analogue of this phenomenon: when a melody is interrupted by bursts of white noise, it is nonetheless heard as a single melody continuing "behind" the bursts of noise. Formulation of the theory is credited to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
