1.4 Combining Afferent and Efferent Signals: Models of head centred motion perception.
Sensory signals relating information about our physical movements, as well as information regarding external object motion, are required in order to preserve a stable and accurate view of the world, and estimate external motion. Space constancy is the visual system’s ability to maintain a view of the outside world that does not jump about and move with an eye movement (Deubel, Bridgeman, & Schneider, 1998; Stark & Bridgeman, 1983). A simple way of achieving this is to add the velocity estimates that are derived from afferent and efferent motion signals. The sum of these estimates would result in head-centred motion. For instance, the image on the retina of stationary objects in the world would gain a motion opposite and equal to any eye movement. As suggested above, reafferent retinal motion should provide a velocity estimate of similar magnitude to the efferent estimates of eye movement. If these two estimates are equal to one another, but have opposite sign, then their sum would correctly suggest null motion.
Figure 1.2 shows a simple schematic detailing the combination or retinal information and eye velocity estimates to generate a perceived motion direction. This diagram is analogous to figure 1.1, showing the integration of signals from a lower ‘detector’ level, at the eye movement and retinal velocity estimate level, and later at an integrator stage, after which the motions have been transformed into the perceived direction. This diagram also illustrates the focus of chapters 2, 3 and 4. Chapter 2 investigates the motion aftereffect (see adaptation section) which follows simultaneous retinal motion and repetitive smooth pur...
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..., 1994). If the extra-retinal signal is altered by the OKN signal, both the eye movement velocity and the perceived velocity alter accordingly. Other evidence does not support an optokinetic potential model, since the predicted changes to optokinetic potential were not observed when background contrast and spatial frequency were manipulated (Sumnall, Freeman & Snowden, 2003). However, the concept that stimulus characteristics which initiate reflexive eye movements could interfere with the voluntary smooth pursuit signal is interesting. The optokinetic-potential model is here considered as an extension of the classical model, since the extra-retinal origin of the pursuit estimate is maintained. Other models have questioned the purely extra-retinal nature of the pursuit speed estimate, and an alternative which includes reafferent information has been proposed.
My scientific concept is how sight effects balance. Balance is the equal distribution of weight. “Balance is controlled by the vestibular system, which includes the eyes, the inner ear, and other sensory systems of the body” (asha.org). The visual system interacts with the vestibular system by using the
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.
The merging of certain senses points to a crossing of signals in the brain. Although the theory is an old one, it has come to the forefront of the scientific researcher's minds, with increased focus on the topic.
The ‘where visual pathway’ is concerned with constructing three dimensional representations of the environment and helps our brain to navigate where things are, independently of what they are, in space in relation to itself (Mishkin & Ungerleider & Macko, 1983).... ... middle of paper ... ... The 'Standard' of the 'Standard'.
The effects of perceptual load on the occurrence of inattentional blindness were demonstrated clearly by experiment. In an experiment conducted by Finch and Lavie in 2007, participants were given identical series of central cross-targets with two arms of clearly different color (blue and green) and slightly different length. Participants were split in two groups, one performing an easy task (low load condition) and the other a harder task (high load condition). The group performing the easiest task only had to make color discrimination between the tw...
The high percentages of individuals who endure this impairment justifies and practically demands future research because the causes are not fully understood. The need for future research can be better emphasized if those with normal vision try to empathize with victims of macular degeneration. One can only imagine how frustrating it must be to receive sensatrions only in the periphery of the retina. Because the macula encompassed the cone rich fovea, which is used to focus on objects, the fovea degenerates as well. This occurence inables individuals to interpret the sensations they experience. Reading, ...
If the image-generating computer 'knows' where the pilot's fixation is, it mage there. The technology to make this possible was developed by a research team headed by Professor Richard Frecker and Professor Moshe Eizenman. The work was carried out in collaboration with CAE Electronics Ltd. of Montreal with financial support from the Natural Sciences and Engineering Research Council of Canada. Their eye-tracker can record and analyze accurately up to 500 eye positions per second.
Mental rotation Mental rotation is another classic cognitive psychology paradigm, which was devised by Roger Shepard at Stanford. To understand how this task works, take a look at the shapes in the top panel (A) of Figure 12.3. The two shapes are the same; the one on the right has been rotated clockwise by about 90°. By contrast, the pair of shapes on the bottom row (B) do not match. If you look carefully, you will notice that they are mirror- Earworms and Imagery 5 images of each other, so that even if you rotate the shape on the left clockwise by 90°, it won’t match up with the shape on the right.
A monocular cue to depth refers perception of motion that only relies on the perception of a single eye. Monocular cues include size: distant objects subtend smaller visual angles than near objects, grain, size, and motion parallax. However binocular cue to depth refers to perception of motion that relies on a two-eyes. Binocular cues include stereopsis, eye convergence, disparity, and yielding depth from binocular vision through exploitation of parallax. Binocular cues are important to the monocular cues due to the rise in depth they offer compared to the single eye monocular cues. Having two eyes increases an individual’s depth perception of close objects that are at two different distances.
The environment provides the information necessary for the equilibrium center to determine which position to place the body in. There are three main places in which information is received: the eyes provide visual information, the ears provide vestibular and auditory information, and the articulations provide proprioceptive information. In general, the eyes help position the body according to different horizontal angles in relation to the ground. The ears allow the body to acknowledge any type of movement, such as acceleration or deceleration, by registering various sounds (1). Movement is also processed in parts of the brain, as well as in the ears.
Donovan, W. L. & Leavitt, L. A. (1980). Physiologic correlates of direct and averted gaze. Biological Psychology, 10, 189-199.
In the process of human infants’ development, infants start to learn how to communicate with the others at the surprising early age, for example: Newborns can follow objects to make saccades to peripheral targets (Farroni et al., 2004);Infants’ responding eye gaze behaviour increase constantly since two months old (Scaife & Bruner, 1975); Cooper and Aslin pointed out that this preference showed up as early as the infants were one month old in 1990. Infants not only can respond to eye contact, vocal cues also are used for gaining more reference information during a communication, particularly when the speech is conducted forward to the infants. It had been reported in many studies that infants show more preference to infant-directed communication
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...
Monocular Video Sequences. ACM Trans. Graph. 29, 4, Article 42 (July 2010), 10 pages. DOI = 10.1145/1778765.1778779 Web. 5 Apr. 2011.
The Eye is the organ of sight. Eyes enable people to perform daily tasks and to learn about the world that surrounds them. Sight, or vision, is a rapidly occurring process that involves continuous interaction between the eye, the nervous system, and the brain. When someone looks at an object, what he/she is really seeing is the light that the object reflects, or gives off.