Vision is one of the most important senses available to human. The vision of the man guarantees his survival by the apprehension of danger and prey, and "takes part in a wide range of behavioural complexes: navigation, balance, object recognition, guidance of social interaction" (Harris and Humphreys, 1991, p179). Vision was a concept tackled by philosophers long before psychologists even existed, the relationship between man, vision, and the world has been one of the most studied. It is not surprising that the anatomy of the visual system is now one of the best understood. The very distinct functional specialization within this system makes it a prime example for the understanding of the brain in its whole. We will first quickly talk about the nature of visual perception before tackling the actual anatomy of the human visual system. We will then explain different methods to give evidence of the previously stated facts and the different research that led to our actual knowledge.
Humphreys and Riddock (1994) showed that 60% of the monkey's cortex is devoted to visual processing, it seems obvious that its importance is colossal. Before them Gregory (1966, p.9) already asked science the following question: "How is information from the eyes coded into neural terms, into the language of the brain, and reconstructed into experience of the surrounding objects?". It seems that we can only perceive the world. "Perception is not determined by stimulus patterns; it is a dynamic searching for the best interpretation of the available data." Gregory(1966). These available data are physical surfaces which create differential reflections of light which are then transmitted to the eye.
Rosinski (1977) categorizes perception into three di...
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...ital lobe, specialized for colour, by McKeffrey and Zeki in 1997.
Some patients face problem in space recognition: Balint (1909) describes deficits in visually guided behaviour, he calls it optic ataxia. Some patients can reach objects with their hand but not describe them. Some patients have the exact opposite problem. ( Jeannerod 1988; Perenin and Vighetto 1988; Goodale et al 1994, 1991)
The visual system is a profoundly specialized setup which analyzes the light stimuli from the visual field of both eyes. The functional segregation is based on three basic components: shape, colour and movement. Previous research in this field was based on monkeys brains, or brain damaged human patients. The anti-localization position Lashley's is no longer followed. Instead, today's research is directed towards now evidence concerning micro-specializations of the brain.
The ultimate goal for a system of visual perception is representing visual scenes. It is generally assumed that this requires an initial ‘break-down’ of complex visual stimuli into some kind of “discrete subunits” (De Valois & De Valois, 1980, p.316) which can then be passed on and further processed by the brain. The task thus arises of identifying these subunits as well as the means by which the visual system interprets and processes sensory input. An approach to visual scene analysis that prevailed for many years was that of individual cortical cells being ‘feature detectors’ with particular response-criteria. Though not self-proclaimed, Hubel and Wiesel’s theory of a hierarchical visual system employs a form of such feature detectors. I will here discuss: the origins of the feature detection theory; Hubel and Wiesel’s hierarchical theory of visual perception; criticism of the hierarchical nature of the theory; an alternative theory of receptive-field cells as spatial frequency detectors; and the possibility of reconciling these two theories with reference to parallel processing.
Another speaker, Margaret Livingstone delves into the visual aspect of our senses. Livingstone mentions how artists recognize things about vision that neuroscientists are not privy to until years later. Livingstone discussed the differentiation between color and lightness, and how the two contribute differently to a work of art. Color is thought of as “comparing activity” whereas light is thought of as “summing them.” Livingstone indicates that the visual system is subdivided into a ventral system and a dorsal system. The ventral system is responsible for object recognition, face recognition, and color. The dorsal system is responsible for navigating through the environment, special organization, and emotional recognition. The ability for humans to see distance and depth is carried via our colorblind part of our visual system. As a result, Livingstone concludes that one cannot see depth and shading unless the luminance is right to convey three-dimensional.
Hubel and Wiesel’s research surrounding area V1 of the primary visual cortex provided one of the first descriptions of the receptive fields in mammals. By flashing various lines along the receptive field, Hubel and Wiesel were able to classify cortical neurons into two distinct groups; simple and complex (Hubel & Wiesel, 1963). The use of manually mapping the receptive fields with simple dots, lines and edges meant that they not only discovered orientation tuning in single neurons, but also described the columnar organisation of ocular dominance and orientation preferences in the cerebral cortex (Ringach, 2004). Although Hubel and Wiesel’s findings were an extreme advance in our understanding of the visual cortex (Wurtz, 2009), it became apparent that there were cells in the visual system that responded to stimuli far more complicated than orientated lines meaning that the cells in area V1 were much more modifiable than Hubel and Wiesel had suggested. In this essay, Hubel and Wiesel’s classic receptive field shall be discussed along with reasons as to why it can no longer offer us a satisfactory explanation into visual perception. First to be discussed are the specific types of cells which were defined in Hubel and Wiesel’s classic experiment into the striate cortex.
According to Dr. Vilayanur Ramachandran, in his movie “Secrets of the Mind,” our vision system is divided into two parts, one with our eyes, and the other with our brain. He also says that there are two different pathways in which our brain uses to “see.” One of these pathways, he calls the evolutionary new pathway (the more sophisticated pathway) in which our eyes see, then the information is sent to the thalamus, and eventually entering the visual cortex of the brain. This pathway is the conscious part of seeing. The other pathway Dr. Ramachandran says is more prominent, as well as evolutionarily primitive. An iguana uses this system of seeing. In this second pathway, information enters through the eyes, and then is sent to the brain stem, which in turn relays the information to the higher center of the brain. Dr. Ramachandran says that this second system is used to orientate our eyes to look at things, especially movement. Dr. Ramachandran has looked at patients with what is known as blind-sight to form his hypothesis.
Vision plays a huge role in the lives of non-human primates. Non-human primates have exceptional binocular vision, due to forward-facing eyes with overlapping visual fields (Prescott). This binocular stereoscopic color vision allows primates to see the world in terms of height, width, and depth, also known as three-dimensional vision (Haviland et al. 2010). Highly developed vision allows the later arboreal primates to judge depth, distance, and location when moving at speed from branch to branch (Haviland et al. 2010). This bino...
Blindsight is often understood as supporting certain claims concerning the function and the status of the phenomenal qualities of visual perceptions. In this talk I am going to present a short argument to show that blindsight could not be understood as evidence for these claims. The reason is that blindsight cannot be adequately described as a special case of seeing. Consequently, it is not possible to draw inferences from it concerning the role of the phenomenal qualities for seeing.
Discuss how Sperry and Gazzaniga’s research has contributed to a greater understanding of brain lateralization and localization.
Sajda P. & Finkle, L.H. (1995) Intermediate Visual Representations and the Construction of Surface Perception. Journal of Cognitive Neuroscience, 7, 267-291.
Ratey, John J., and Albert M. Galaburda. A User's Guide to the Brain: Perception, Attention, and
Perception plays a huge role in someone’s life. “When a distinction is made between sensation and perception, sensation is frequently identified as involving simple “elementary” processes that occur right at the beginning of a sensory system, as when light stimulates receptors in the eye. In contrast, perception is identified with complicated processes that involves higher-order mechanisms such as understanding and memory that involve activity in the brain” (Goldstein, 1980, p. 7). It is simply the ability to see, hear, or become aware of something through the five senses. Perception aids us to navigate through the world, avoid danger, make decisions, and prepare for action.
Have you ever thought what actually influences our perception of stimuli we encounter on a daily basis? The topic of this paper is perception. Many times, the way we take in information from the world, is entirely up us as an individual but most times perception is influenced by external factors, which cannot be controlled. Perception is an opinion held by individuals regarding how things seem in the real world. The area regarding perception interests me greatly because I feel it is very interesting how different individuals have different ways to perceive the same exact information. Perception is the process in which we learn about the world around us. Specifically, I want to learn what mechanisms truly influence perception and how those affect our daily lives.
In A New Theory of Vision, Berkeley attempts to show that all experience is reducible to sense data by exploiting two types of argument. At times he exploits a scientific account of perception and of the functioning of the perceptual organs, while at other times he uses the argument from illusions.
Vision is a physical sense that uses light to provide information to the brain in order to make conclusions about the surroundings. The human eye is an intricate organ that works best when there is an adequate supply of light. Our eyes have been often compared to cameras in that a camera filters light through the lens, controls the intensity with an aperture and focuses the image onto a film. Light coming into an eye is filtered through the cornea, the iris regulates how much light comes through, and then it is focused by the lens onto the retina.
There are many different Visual Perception principles in perception. The main principles are Gestalt. Gestalt is a German word meaning 'form' or 'shape'. Gestalt psychologists formulated a series of principles that describe how t...
Blakslee, S. (1993, August 31). The New York Times. Retrieved May 2, 2014, from www.nytimes.com: http://www.nytimes.com/1993/08/31/science/seeing-and-imagining-clues-to-the-workings-of-the-mind-s-eye.html