Animals with a saccade and fixate eye movements strategy. Why should this be so - Essay Example

?Saccade and fixate By Presented to Saccade and fixate Introduction In animals the visually elicited spikes have been supported by the modulation in Neuronal excitation. Naturally movements of the eye introduce artifact recordings that are done by the electroencephalographic commonly known as the (EEG). It is believed that the Neutral activity is measured with this electroencephalography and at times Magneto encephalography (MEG) that gives a very weak signal (Buswell, 1935). The amplitudes are few microvolts’ that work co-currently. The saccade is the word use to refer to the fast eye movement. The eye being on organ in animals can be referred to as a device the same as in a machine that is very useful with the issue of providing sight to the animal as per that matter (Hay hoe, 200). When these simulations are done in a quick movement then this is termed as Saccade where both the eyes do move in the same direction. The focus that comes with the eyes moving straight to the area of interest or concern has been researched as being the fixation. For instance animals are able to detect danger and keep a sharp eye focus on the enemy or at times it might not necessary be danger but the animal has spotted its prey. This will cause more concentration as there is need for food (Johansson, 2001).. The eye at this point has been used for locating the food and then the hunting will take place. This strong focus is what is being referred to as fixation. There are always some small eye vibration that so important in visibility moreover to stand still objects. There is circular kind of movements that will be of great importance in giving a clear and stable image. When we refer to the issue of visual fixation we do refer to the starring of a given point. There is need for the co-ordination of the eye the head and other body parts that will bring Saccade and visual fixation to inter-marry. These bring about speed of responding to events and situations. Let’s take an example of a cheater hunting a gazelle in the field. The Saccade will occur when the cheater will focus and move as close as possible to the prey and the fixation of the eyes will be that it won’t change its focus on the prey (Regan, 2000). On the other hand when the gazelle notices the enemy it will moves with speed to save its life as the cheater remains focused to the prey to keep it alive or else it will die of hunger. Now the mechanics on the three fixations does occur when the eye movement is given the category of ocular drift. There are micro saccades and then the ocular micro tremors (Brain, 2006). Their function is to perceptual. Oscillation that occurs from this kind of fixation has not been well detected. The cat family, the primates the avian such as the eagle and owl has been reported to have the best fixation practices. They have a very sharp connection between the eye and the brain that helps the to be well adaptable their environment. They connect the neurons in various different visual parts and connect to their brain perfectly (Brain, 2006). This shows that the text processing is ‘on-line’ on a fixation by the fixation basis. In a similar way, difficult words often result in longer fixations. This indicates that cognitive process operates within single fixations. Like music playing, copy typing has a motor output. According to (Butsch, 1932),a typist of any skill levels always attempt to maintain the eyes about one second ahead of the letter he is currently typing. This is much the same as it is in music reading (Butsch, 1932). In both musical sight-reading and text reading, the gaze must move progressively to the right side. However, it is more complicated in that there are two staves -for key board players- from which the notes are must be acquired. As recorded by Weaver (1943), eye movements of trained pianists gets their gaze alternated severally between the lower and upper staves. This alternation clearly shows that notes that are to be played together must be are viewed at different times. The the upper stave fixations were much longer than those on the lower stave , most likely because more notes are acquired during the upper stave fixation. Musical sight-reading, Reading, and typing—are similar in that they involve a continuous processing of a flow of visual information which taken in as a series of clear stationary fixations. The information is converted to a stream of muscular activity of various kinds after transition. In the case of silent reading, In each case, the processing time is about a second (Patla, 1999). When the appropriate action has been accomplished, the original information is overwritten in such a way that the operation is more like a production line than a conventional memory system. Viewing a photo has no obvious output. The patterns of eye movement on the photo are less constrained than in the previous activities (Buswell, 1935). Fixation patterns changes during the viewing period, and spread out more evenly across the picture. It’s suggested that the viewer changes to a more detailed study of limited regions from an initial quick survey (Buswell, 1935). The study of gaze movements of head-free, fully mobile subjects requires the development of eye trackers that are mounted on the head and not on the bench. A head base view of the scene ahead is provided by most of the new generation of eye trackers, with the direction of regard represented by a specific spot or crosshair. Frequently, the motor behavior of the specimens is also recorded. When crossing a leveled ground, walkers rarely look at where they are going in order to safely step. In more difficult terrain however, they tend to fixate locations of their future footfalls. The obvious question that arise is how far must they look ahead in order to gather the information they need to make a safe footfall. Patla et al. (1999) used a light spot indicating the location of the undesired footfalls and found that these alternative placements were not selected at random and that the foot could be redirected to a new location within the duration of the preceding step, (Patla, 1999). They were generally directed to the location that minimized displacement of the foot from its normal footfall, causing the least disruption to both dynamic stability and locomotors muscle activity. Thus, it appears that footfalls are planned up to two steps into the future while adjustments can be made in within one step if need be required. When we change direction, the body axis rotates since it is carried by the feet. The direction change is indicated by prior instruction about the route or the onset of a light at the new path end point. The finding was that turns ware accompanied to the new destination by an eye saccade, initiated at the same time as a movement of the head (Shioiri, 1989). The combination of head and eye brought head and gaze into line with the direction of the new aim as the body turn was being made. Hence, gaze movements into turn anticipate body movement. The authors argue that pre-aligning of the head axis provides an external frame that can be used to control the rest of the body. Similar occurrence is noted when body turns are made without any forward motion and when turning a corner in a car. (Land, 1999) At times, the eye must be used for two different functions simultaneously. Since there is only one fovea and due to poor off-axis vision, the visual system resorts to time-sharing. A very good example of is when a driver is negotiating a bend and needs to look at the tangent point while passing a cyclist whom he checks on repeatedly (Shioiri, 1989). From the record, the driver alternates gaze between cyclist and tangent point several times and spends half a second on each. The lower record indicates that he steers by the edge of the road. This means that the coupling between hand and eye has to be turned off as he views the cyclist. Thus, the gaze not only switches between tasks but also the whole of his visual-motor control system. On the other hand, some ball sports are very fast. Consequently, there is no enough time for the player to use his usual ocular-motor machinery. Within a fraction of a second (as seen in baseball or cricket) batter has to formulate a properly timed and aimed stroke and judge the trajectory of the ball. The required accuracy is a few centimeters in space and a few milliseconds in time (Regan, 1992). In half a second one or at the most two saccades will occur and the speeds involved result into a smooth pursuit along of the ball’s trajectory. Practitioners of these sports usually use their eyes to gather the information they need in order to accomplish their roles. It is clear that eye movements play a vital role in the organization of our actions and that generally the eyes begin to collect information prior to the action's commencement (Johansson, 2001). Eye movements, thus, are a planned-in part of every action sequence and are not just summoned up when more information is needed. The eyes tend to look at points that are informative for the ongoing action. Good examples include: food preparation where the object is undergoing manipulation, steering it is the tangent point, while in ball games it is the bounce point. The spatial scale of the task determines the accuracy of these points is targeted by the gaze (Regan, 1992). Hence, in reading every fixation takes in about seven letter spaces (Johansson, 2001). This is the standard print at forty centimeter meaning that saccades are approximately1.331 long. Thus, from any one detected letter, the maximum angular distance of the fovea center is half of this which is 0.671. On the other extreme, the average size of ‘within object’ saccades in both sandwich and tea making was about 81, giving a maximum eccentricity target of 41 (Land M. T., 2001). This is six times greater than in reading. The difference, presumably, is because of the large size of culinary objects as compared with letters. Many other estimates fall between these two extreme values. A good example is (Johansson, 2001) who used a high-precision eye tracker to study the performance in a task in which a bar was grasped and lifted to make contact with a target switch avoiding a projecting obstacle on the way (Regan, 1992). They found out that the eyes always fixated certain distinct points (the target, the grasp site, and the surface to which the bar returned) frequently, fixated the obstacle and the tip of the bar. They estimated fixation precision by determining the sizes of circles that enclosed ninety percent of the fixation points for all nine subjects: which were 3.31 for the bar tip and 5.61 for the obstacle. For the target, most fixations were within a 31percent circle and they, as a result, regard 31 as the diameter of the ‘functional fovea’ for this task. This implies a maximum target eccentricity of 1.51 (Johansson, 2001). Shioiri studied the extraction of information from pictures, using a window which was contingent on eye-position (Shioiri, 1989). They found that the maximum area in which high-resolution pictorial information was extracted was about 101 across and larger windows provided no extra information. This shows that no further ‘useful resolution’ is available beyond 51 from the fixation point. This, however, cannot be universally true. Finally, Land, in his studies found that subjects could make accurate single head-and-eye saccades to appropriate objects that were as far as to 501 from the current fixation point (Land M. T., 2001). Even if position memory is involved here, some information that allows object identification must be available even in the far periphery. In conclusion, there has been great studies done and have revealed that we can state that saccade and fixation of the eye movement are vital to the animals who use it. It increases the degree of soundness of the decisions made after making a visual judgment. Biography Brain, R. (2006). Fixational eye movements and motion perception. Tokyo: University of Tokyo. Buswell. (1935). How People Look at Pictures. A Study of the Psychology of Perception in Art. , 22-30. Butsch, R. (1932). Eye movements and the eye–hand span in. Hayhoe, M. (2000). A Functional Account. Vision Using Routines: , 43-63. Johansson, R. W. (2001). eye–hand coordination in object manipulation. 6917–6932. Land, M. F. (1999). why animals move their eyes. Motion and vision: . Land, M. M. (1999). The roles of vision and eye movements in the control of activities of daily living. 1311–1328. Land, M. T. (2001). Steering with the head: the visual strategy of a racing driver. Laurent Itti, C. K. (May 1999;). A saliency-based search mechanism for overt and covert shifts of visual attention. Martinez-Conde, S. M. (2000). The Extraordinarily Rapid Disappearance of Entoptic Images. Proceedings of the National Academy of Sciences of the USA , 8001–8004. Patla, A. P. (1999). What guides the selection of alternate foot placement during locomotion in humans. Pritchard R.M., H. W. (1960). Visual Perception Approached by the Method of Stabilized Images. (Vol.14). Canada. Regan, D. (1992). Visual judgments and misjudgments in cricket, and the. Perception 21, 91–115. Shioiri, S. I. (1989). Useful resolution for picture perception as a. 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