The eye is the main body organ with the help of the brain that deals entirely with vision. There have been main theories that tend to explain how vision system performs its function. These theories relied on assumption. The first school of thought was based on the emission theory, that said vision occurred when rays emanated from the eye fall on the object, and an image is seen on the eye by refraction of the rays in the eye (Kristi. 45).
The second school of thought was what was called intro-mission approach. This thought came close to the modern theories. The intro-mission approach relied on the principle that 'like is only known to like'. The founders of this school of thought stated that the eye had an internal fire that interacted with the external fire and this made vision possible. The two schools of thought remained speculating due to lack of experiment to prove their proposal.
The Eye and Ear Senses
There were different proposals that were fronted as to how the eye and the brain made sense of the visual world, and this lead to the study of the vision system. Neuroscience came into being, to air out all the speculations and came up with a concrete idea of how the mammalian vision system works with more emphasize to mankind.
The vision system, is a complex and complicated system that involved the unconscious interference, although this was also based on the assumption that; light came from above, objects are seen and recognized upright and objects are not viewed from below(Kristi,12).
Psychologists raised many of the research questions that were from vision scientist and came up with the law of organization, which has led to change of perception and shown vision components' as an organized structural process, or pattern that follows a laid down sequence. Six factors that determined how visual system automatically groups elements into sequence, is what this theory proposed and they are as follows; Distance, Similarity, size, Symmetry, motion, and continuity. All this was organized under one process, the visual system.
It mainly functions properly in the presence of light. Different animals can see through different light spectrum. For example, bees can see through the ultraviolet light which man cannot see through.
Visual systems have the following components: the eye, optical nerve, optic tract, lateral geniculation, visual association cortex. This is part of the central nerve system that enables animals to make sense, from visual details they perceive from the environment. This system completes a number of tasks including interpretation of light rays to the eyes, and gives a clear picture of the perceived image of the world and its objects. The eye is a complex organ that allow light to pass through it at the cornea and refracted further by the lens. The cornea and the lens then project the refracted image to the retina.
The retina has a large number of photoreceptor cells, which are made up of molecules rich in proteins. Humans have two types of protein molecules involved in conscious vision. The proteins molecule (opsin) mainly absorbs a particle of light (photon), and relays a signal to the brain cell through a signal transduction pathway, which leads to hyper polarization of the photoreceptor system (David 45).
The eye can be able to see objects through the dark in different animals, while in others, can only see objects in a good lighted environment, and this is due to the presences of rods and cones found in the retina. Rods are situated in the periphery of the retina and functions at low levels of light. This is very common to animals that hunt or are active at night, an example is a dog. It can see clearly in the dark this due to the numerous numbers of rods in its eyes. Cones are situated at the center of the retina. Cones primarily distinguish features of the visual world including color at normal light transmission.
The photoreceptor in the retina usually synapses to the bipolar cells and to the ganglion cells, which in turn conduct action to the brain. High communication between the neuron in the retina led to a visual communication, this is through absorption of light of different wave length. This leads to transmission of information from the retina to the brain by the neurons. The presences' of rod in the retina enable it to adapt to different light exposure during the day, by changing its shape. This is called bleaching and as a result a nerve impulse is created and sent to the brain for interpretation,and course of appropriate action. The signals to the brain pass along the optic nerve (Christer, 23).
In the brain, a group of photosensitive ganglion cell sends the signals to the papillary reflex through the retina hypothalamic tract to areas involved in the control of the circadian rhythms. The photosensitive ganglion cell also plays a major role in the mediation between the unconscious and the conscious vision (Walter 23).
At the base of the hypothalamus in the brain, the optic nerve from the two eyes meet and cross each other at a point called optic chiasm. Here the different information from both eyes is combined and distributed according to field of view. It's in the right and left side of the brain.
The two optic tracts passing the information from the right and left visual fields, enters the brain thalamus side through the lateral geniculate nucleus which is a processing center and a sensory relay part of the brain. Information from the brain is transmitted to the visual cortex by the optic radiations nerves that are situated at both sides of the brain. Visual cortex being the largest system in the mammalian brain, is responsible for processing visual images from the thalamus of the brain, here all the major components of the image can be determined be it color, motion also edge and corner are detected (Christer 34).
The eye and brain make sense of the visual world by combination of different sensory information, relayed by the eye to the brain. For one, to make a good sense of the world; he or she needs more than one sense. Although from vision we can perceive some senses like depth, but it will be apparent from a perspective, for example, a tall building in a film, will relay the length of that building as being tall. A long verandah in a film will clearly indicate the depth or that building or the entire horizontal length of that particular building.
Combining sensory information may result in sensory fusion; this is inability to separate information, sending the overall perception in the brain. Tension and alertness of an individual leads to a lot of sensory information into the brain in a manageable way, seen, a large area of the brain is used in vision, if information streams in the brain in a non manageable way, it leads to chaos (Walter, 76).
To make cognition by the brain and eyes, it entirely depends on the brain wave. If the brain waves can be artificially manipulated, then the speed of cognition will be improved.