question: Why does our vision not shake and wiggle like a video of say, someone mountain biking?
comment: Our eyes are constantly shifting and are able to move to maintain smooth vision while a bike camera is locked in place and bounces on a trail same as you feel while riding it
passages: The visual system in the brain is too slow to process that information if the images are slipping across the retina at more than a few degrees per second. Thus, to be able to see while we are moving, the brain must compensate for the motion of the head by turning the eyes. Another specialisation of visual system in many vertebrate animals is the development of a small area of the retina with a very high visual acuity. This area is called the fovea, and covers about 2 degrees of visual angle in people. To get a clear view of the world, the brain must turn the eyes so that the image of the object of regard falls on the fovea. Eye movement is thus very important for visual perception, and any failure can lead to serious visual disabilities. To see a quick demonstration of this fact, try the following experiment: hold your hand up, about one foot (30 cm) in front of your nose. Keep your head still, and shake your hand from side to side, slowly at first, and then faster and faster. At first you will be able to see your fingers quite clearly. But as the frequency of shaking passes about 1 Hz, the fingers will become a blur. Now, keep your hand still, and shake your head (up and down or left and right). No matter how fast you shake your head, the image of your fingers remains clear. This demonstrates that the brain can move the eyes opposite to head motion much better than it can follow, or pursue, a hand movement. When your pursuit system fails to keep up with the moving hand, images slip on the retina and you see a blurred hand.
   In many animals, including human beings, the inner ear functions as the biological analogue of an accelerometer in camera image stabilization systems, to stabilize the image by moving the eyes. When a rotation of the head is detected, an inhibitory signal is sent to the extraocular muscles on one side and an excitatory signal to the muscles on the other side. The result is a compensatory movement of the eyes. Typically eye movements lag the head movements by less than 10 ms.
  
  Section::::See also.
  
  BULLET::::- Adaptive optics
  
  BULLET::::- Deblurring
  
  BULLET::::- Heligimbal
  
  BULLET::::- Hyperlapse
  
  BULLET::::- Motion compensation
  
  BULLET::::- Shaky camera
   Wiggling works for the same reason that a transitional pan (or tracking shot) in a film provides good depth information: the visual cortex is able to infer distance information from motion parallax, the relative speed of the perceived motion of different objects on the screen. Many small animals bob their heads to create motion parallax (wiggling) so they can better estimate distance prior to jumping.
  
  Section::::Gallery.
  
  BULLET::::- The music video for "Broccoli" by D.R.A.M. makes extensive use of the wiggle stereoscopy effect using multiple frames per loop.
   Lesion studies have also supported the role of MT in motion perception and eye movements. Neuropsychological studies of a patient unable to see motion, seeing the world in a series of static 'frames' instead, suggested that V5 in the primate is homologous to MT in the human.
   However, since neurons in V1 are also tuned to the direction and speed of motion, these early results left open the question of precisely what MT could do that V1 could not. Much work has been carried out on this region, as it appears to integrate local visual motion signals into the global motion of complex objects.
   Another option for reducing the impression of jerkiness is to reduce the time between the frames of a wiggle image.
  
  Section::::Perception.
  
  The sense of depth from wiggle 3-D images is due to parallax and to changes to the occlusion of background objects.
  
  Although wiggle stereoscopy permits the perception of stereoscopic images, it is not a "true" three-dimensional stereoscopic display format in the sense that wiggle stereoscopy does not present the eyes with their own separate view each.
   Several methods of recording have been developed to observe these minuscule events, the most successful being the piezoelectric strain gauge method, which translates eye movement through a latex probe in contact with the eye leading to piezoelectric strain gauge. This method is used in research settings; more practical adaptations of this technology have been developed for use in clinical settings to monitor the depth of anesthesia. Despite the availability of these methods, tremor remains more difficult to measure than other fixational eye movements, and studies addressing medical applications of tremor movements are rare as a result. Some studies have, nevertheless, pointed to the possibility that tremor movements may be useful in assessing the progression of degenerative diseases including Parkinson's disease and multiple sclerosis.
   The apparent stereo effect results from syncing the timing of the wiggle and the amount of parallax to the processing done by the visual cortex. Three or five images with good parallax may produce a better effect than simple left and right images.
   BULLET::::- John Napier, a primatologist, claimed that "if the movie was filmed at 24 frame/s then the creature's walk cannot be distinguished from a normal human walk. If it was filmed at 16 or 18 frame/s, there are a number of important respects in which it is quite unlike man's gait." Napier, who published before Dahinden and Krantz, contended it was "likely that Patterson would have used 24 frame/s" because it "is best suited to TV transmission," while conceding that "this is entirely speculative."
   These results indicate that the human perceptual system neglects many useful pieces of information when it comes to spatially localizing target displacements occurring during a saccade. Surprisingly, in contrast to the perceptual system, the motor system is able to access precise spatial information in order to render precise motor actions during a saccade (Bridgeman, Lewis, Heit, & Nagle, 1979; Prablanc & Martin, 1992).
  
  Section::::Elimination.
   The inability to perceive motion is called akinetopsia and it may be caused by a lesion to cortical area V5 in the extrastriate cortex. Neuropsychological studies of a patient who could not see motion, seeing the world in a series of static "frames" instead, suggested that visual area V5 in humans is homologous to motion processing area MT in primates.
  
  Section::::First-order motion perception.
   Persistence of vision should be compared with the related phenomena of beta movement and phi movement. A critical part of understanding these visual perception phenomena is that the eye "is not a camera", i.e.: there is no frame rate for the human eye or brain. Instead, the eye/brain system has a combination of motion detectors, detail detectors and pattern detectors, the outputs of all of which are combined to create the visual experience.
   Section::::Vision.:Smooth pursuit movement.
  
  Eyes can also follow a moving object around. This tracking is less accurate than the vestibulo-ocular reflex, as it requires the brain to process incoming visual information and supply feedback. Following an object moving at constant speed is relatively easy, though the eyes will often make saccadic jerks to keep up. The smooth pursuit movement can move the eye at up to 100°/s in adult humans.
  
  It is more difficult to visually estimate speed in low light conditions or while moving, unless there is another point of reference for determining speed.
  
  Section::::Vision.:Optokinetic reflex.
   The application of optical flow includes the problem of inferring not only the motion of the observer and objects in the scene, but also the structure of objects and the environment. Since awareness of motion and the generation of mental maps of the structure of our environment are critical components of animal (and human) vision, the conversion of this innate ability to a computer capability is similarly crucial in the field of machine vision.
   The first description of what is now known as ocular microtremor was made in 1934 (4). More recent studies are less common for ocular microtremor than for other fixational eye movements. Some have suggested that the reason ocular microtremor studies are more rare may be because of the difficulty inherent in measuring microtremor. It is contentious whether ocular microtremor assists vision. Visual processes deteriorate rapidly in the absence of retinal image motion, with Stabilized Images.
  
  Some have suggested that tremor may not be a distinct eye movement at all.
  
  Section::::See also.
  
  BULLET::::- Fixational eye movements
  
  BULLET::::- Afterimage
  
  BULLET::::- human eye
   Humans, like all known things in the universe, are in constant motion; however, aside from obvious movements of the various external body parts and locomotion, humans are in motion in a variety of ways which are more difficult to perceive. Many of these "imperceptible motions" are only perceivable with the help of special tools and careful observation. The larger scales of imperceptible motions are difficult for humans to perceive for two reasons: Newton's laws of motion (particularly the third) which prevents the feeling of motion on a mass to which the observer is connected, and the lack of an obvious frame of reference which would allow individuals to easily see that they are moving. The smaller scales of these motions are too small to be detected conventionally with human senses.
   Section::::Anatomy.:Neuroanatomy.
  
  The brain exerts ultimate control over both voluntary and involuntary eye movements. Three cranial nerves carry signals from the brain to control the extraocular muscles. These are the oculomotor nerve, which controls the majority of the muscles, the trochlear nerve, which controls the superior oblique muscle, and the abducens nerve, which controls the lateral rectus muscle.
  
  In addition to the movement of muscles, numerous areas in the brain contribute to involuntary and voluntary eye movements. These include providing the conscious perception of vision, as well as areas that facilitate tracking.
  
  BULLET::::- Brain
  
  BULLET::::- Cerebral cortex
   In most cases the support constraint imposed is a priori in that it is modified by the researcher based on the evolving image. In theory this is not necessarily required and algorithms have been developed
   The middle temporal visual area (MT or V5) is a region of extrastriate visual cortex. In several species of both New World monkeys and Old World monkeys the MT area contains a high concentration of direction-selective neurons. The MT in primates is thought to play a major role in the perception of motion, the integration of local motion signals into global percepts, and the guidance of some eye movements.
  
  Section::::Middle temporal visual area (V5).:Connections.
   The most precise research is done using single-cell recordings in the primate brain. This research has yielded areas important to motion perception in primates such as area MT (middle temporal visual area), also referred to as V5, and area MST (medial superior temporal area). These areas contain cells characterized as direction cells, expansion/contraction cells, and rotation cells, which react to certain classes of movement.
  
  Section::::Neuroanatomy.:Neuroimaging.
   BULLET::::- The latter (e.g., Google Glass, GoPro), are commonly mounted on the head, and capture conventional video (around 35fps) that allows to capture fine temporal details of interactions. Consequently, they offer potential for in-depth analysis of daily or special activities. However, since the camera is moving with the wearer head, it becomes more difficult to estimate the global motion of the wearer and in the case of abrupt movements, the images can result blurred.
  
  In both cases, since the camera is worn in a naturalistic setting, visual data present a huge variability in terms of illumination conditions and object appearance.
   Humans and many animals do not look at a scene in fixed steadiness; instead, the eyes move around, locating interesting parts of the scene and building up a mental, three-dimensional 'map' corresponding to the scene (as opposed to the graphical map of avians, that often relies upon detection of angular movement on the retina). When scanning immediate surroundings or reading, human eyes make saccadic movements and stop several times, moving very quickly between each stop. The speed of movement during each saccade cannot be controlled; the eyes move as fast as they are able. One reason for the saccadic movement of the human eye is that the central part of the retina—known as the fovea—which provides the high-resolution portion of vision is very small in humans, only about 1–2 degrees of vision, but it plays a critical role in resolving objects. By moving the eye so that small parts of a scene can be sensed with greater resolution, body resources can be used more efficiently.
   It can also be noted that there are different types of eye movements: fixational eye movements (microsaccades, ocular drift, and tremor), vergence movements, saccadic movements and pursuit movements. Fixations are comparably static points where the eye rests. However, the eye is never completely still, but gaze position will drift. These drifts are in turn corrected by microsaccades, very small fixational eye-movements. Vergence movements involve the cooperation of both eyes to allow for an image to fall on the same area of both retinas. This results in a single focused image. Saccadic movements is the type of eye movement that makes jumps from one position to another position and is used to rapidly scan a particular scene/image. Lastly, pursuit movement is smooth eye movement and is used to follow objects in motion.
   BULLET::::1. The refractive power of the lens is not typically sufficient to form an image on the photoreceptor layer.
  
  BULLET::::2. Dorsal ocelli ubiquitously have massive convergence ratios from first-order (photoreceptor) to second-order neurons.
   Section::::Ocular microtremors.:Mechanism.
  
  Although originally thought to stem from spontaneous firing of motor units, the origin of ocular microtremors is now believed to be in the oculomotor nuclei in the reticular formation of the brainstem. This new insight opened the possibility of using ocular tremors as a gauge for neuronal activity in that region of the central nervous system. More research must be done, but recent studies strongly suggest that decreased activity in the brainstem correlates with decreased frequency of OMTs.
  
  Section::::Ocular microtremors.:Medical application.
  