Once a target object is identified, smooth pursuit eye movements are used to track the object as we, or the object, move through the environment. Smooth pursuit eye movements are slow eye movements that follow a target and are used to maintain its position on the fovea. The smooth pursuit eye movements studied here are conjugate with the eyes moving together and the angle between them preserved. A visual stimulus is usually required to initiate a smooth pursuit eye movement (Rashbass, 1961). Although, by degrading the available retinal information, to the extent that perceived motion was either inaccurate or illusory, Steinbach (1976) reported that smooth pursuit only requires an ‘appreciation of the object in motion with respect to the observer, regardless of retinal stimulation’. Smooth pursuit can be elicited by non-visual information, with proprioceptive and tactile information proving effective for both the initiation and maintenance of pursuit (Berryhill, Chiu, & Hughes, 2006).
Smooth pursuit eye movements are most accurate up to around 30deg/s, but fail to accurately keep up with faster stimuli (Robinson, 1965). Predictable wave forms have proved to be excellent targets for inducing accurate smooth pursuit (Stark, Vossius & Young, 1962; Dallos & Jones, 1963; Yasui & Young, 1984), and were employed in the studies reported here. Whilst the initiation of pursuit usually has a time delay of around 150ms this can be avoided using a predictable wave form (McHugh & Bahill, 1985). The direction of smooth pursuit also plays a role, with the best gains being achieved during horizontal pursuit in humans (Rottach et al., 1996).
1.2.2 Saccades
Saccades are ballistic eye movements that rapidly move the eye to a point o...
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...(von Holst and Mittelstaedt, 1950). von Holst and Mittelstaedt suggested that the signal sent to control the extra-ocular muscles is additionally copied to the perceptual centre of the brain. Von Holst and Mittelstaedt provided evidence for an extra-retinal efferent copy by inverting the head of a fly (von Holst and Mittelstaedt, 1950, in Rosenbaum, D.A., 2009). This reversed the relationship between visual motion and the internal estimate of physical motion during flight. Flying to the right provided inaccurate feedback that the fly was moving to the left. In trying to compensate for the incorrect feedback and regain it’s heading, the fly travelled in circles, in a positive feedback loop. The fly moved normally in darkness. The motion perception mechanisms of the fly had been distorted in ways which could not be predicted by changes to retinal motion alone.
Sullivan, G. D., Georgeson, M. A., & Oatley, K. (1972). Channels for spatial frequency selection and detection of single bars by the human visual system. Vision Research, 12, 383-94.
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.
Studying gaze behavior (where someone looks) is a very important area of research particularly in domain of behavioral psychology. Gaze behavior can, for instance, indicate the amount of attention paid in certain tasks and whether the performance is natural or not. Also, it can indicate the level of competence and experience of the user. Therefore, it can be used as an evaluative tool.
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...
A prominent phenomenon in the field of visual science is the motion after-effect (MAE) which is believed to provide a way of bringing together current knowledge of neurophysiology with a measurable visual phenomenon. The MAE is described as a visual illusion produced by viewing any number of motion types (i.e. lateral or vertical linear, spiral, radial or rotation). By viewing a moving physical object for a period of time until the eyes is adapted to the motion. When the motion of the object is stopped, but viewing remains focussed on the object, the viewer may report a slower, reversed/negative movement of the now stationary object (Mather et al, 1998).
Observer Performance and Visual Search." Journal of Digital Imaging 22.4 (2009): 363-8. ProQuest. Web. 9 May 2014.
Objects that are conveyed by the senses are such as “hard,” “red,” “loud,” and the like. Some are combinations of more than one simple idea derived from more than one sensory input. In the case of “fast,” the speed of something can both be derived from seeing motion as well as feeling motion. Objects conveyed by the operations of the mind are such a...
Gorilla in our midst: sustained inattentional blindness for dynamic events, contrary to popular belief, is not about gorillas in the zoo. The entire article is a focus upon inattentional blindness, which is a lot more common in situations than one were to believe. The focus of inattentional blindness is brought on by a study that includes many volunteers, mainly undergraduate students in the attempts to point out that one can be so focused on one thing that they could completely miss a gorilla coming into the room, or some other obscure factor that occurs without anyone noticing. Through multiple sessions of differentiating experiments, Daniel J. Simmons and Christopher F. Chabris from Harvard University were able to produce further insights
Although the objectives of the two experiments I discussed were different, result were the same regardless as to what the differences might have been. In all experiment including the one I did, results were concurrent. Findings supported the hypothesis that was set forth: As angular rotation increased, reaction time will also increase. Thus, showing reaction times do serve as an appropriate method for analyzing how quickly the brain reacts to mental rotations of images.
Ratey, John J., and Albert M. Galaburda. A User's Guide to the Brain: Perception, Attention, and
Muller, N. G., Bartelt, O. A., Donner, T. H., Villringer, A. & Brandt, S. A. (2003). A physiological correlate of the “zoom lens” of visual attention. The Journal of Neuroscience, 23(9): 3561-3565.
As with the mental map experiments, the fact that reaction time depends directly on the degree of rotation has been taken as evidence that we solve the...
Athletes must accomplish amazing feats of balance and coordination of the body. As scientist, Mikhail Tsaytin discovered in the 1970s, acrobats can successfully make a two person human tower in the dark, but after adding a third acrobat, not even the most talented can maintain the balance required to keep the tower intact while in the dark (1). What does darkness have to do with it? The point is that balance relies on at least three signals coming from the body, and one of those is sight. Once you eliminate one of these signals, the body cannot accomplish the required task. In addition to sight, signals coming from muscles and joints, called proprioceptors are sensitive to changes in position. The third contributor to the human tower and the topic of discussion of this paper is the vestibular system. A three-person human tower in the dark must not have enough information coming from the vestibular and proprioceptive systems to function without vision, whereas the two-person tower did have enough information.
Classical theories demonstrating the inattentional blindness paradigm are (1) the perceptual load, (2) inattentional amnesia and (3) expectation.