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Are The Eyes Part Of The Brain

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What Part Of The Brain Controls Color Vision

Are Your Eyes Part of Your Brain?

There is a particular part of the occipital lobe that handles color vision. Its called the visual cortex. There are two visual cortexes, a left and a right one on each occipital lobe.

For example, when you see an apple, the apples light gets picked up by the photoreceptors inside the eye . Rods and cones receive the wavelengths of light given off by the appleespecially the cones since theyre the eyes color receptor.

The cones send the impulse through the optic nerve to the visual cortex in the occipital lobe. The brain processes this input based on how many cones were activated and the signals strength. Thats how you see the color of the apple is red.

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Neural Control Of Saccades

Saccades and fixations work together to supply the brain with the information it needs to create a mental picture of the world, but the brain is involved in controlling where the eyes will move next. The brain needs to tell the eyes how far and in which direction they should move. When something attracts your attention and you direct your foveae toward it, two brain structures are important in telling the eyes when and how to move: the superior colliculus and the frontal eye fields.

The region of the brain called the superior colliculus takes information from your eyes, ears, and other senses and uses that information to move your eyes toward things that catch your attention . For example, if you are at school and hear the fire alarm go off in the corner of the room, your eyes will likely move toward the direction of that sound without you even thinking about it. The superior colliculus tells your eyes when and where to move, but it also helps control how you turn your head and shoulders. This is important because sometimes what you want to look at is out of the range of your eye movements. If a noise grabs your attention from behind you, for instance, you would need to move more of your body than just your eyes to be able to see what was causing the noise.

The Color System Of The Eye

Cone cells contain a pigment through which light must pass beforereaching the receptor. There are three pigments: One passes violet,with a wavelength of 430 nm one passes blue-green, with a wavelengthof 530 nm and the last pigment passes yellowish-green, with awavelength of 560 nm. In fact, these optical filters have filterskirts, meaning they pass light of other wavelengths, but with reducedsensitivity. Any monochromatic light actuallyactivates cone cells of multiple pigments, but at differentsensitivities. This also explains why we can see light with wavelengthsshorter than 430 nm, and longer than 560 nm.

No conecells, however, can truly perceive red. The closest we really get isyellowish-green. What we call red is really an opticalillusion, supplied by the brain by means of extrapolation. Oursensitivity to red is dramatically reduced compared to other colors,and our visual acuity in the red end of the spectrum is extremely bad.Everyone knows not to focus a projector using a redtest pattern. This is why the red gun in color-video equipment needsthe least resolution to be satisfactory .

Folk wisdom has many sayings about believing what you hear andbelieving what you see. The visual sense is just as prone to illusionas the auditory pathway, and equally filled with mystery andmisunderstanding. Maybe belief should rest not on the particularsensory pathway but rather on our understanding of the ways and meansthrough which we view the world.

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Blood Supply To The Brain

Two sets of blood vessels supply blood and oxygen to the brain: the vertebral arteries and the carotid arteries.

The external carotid arteries extend up the sides of your neck, and are where you can feel your pulse when you touch the area with your fingertips. The internal carotid arteries branch into the skull and circulate blood to the front part of the brain.

The vertebral arteries follow the spinal column into the skull, where they join together at the brainstem and form the basilar artery, which supplies blood to the rear portions of the brain.

The circle of Willis, a loop of blood vessels near the bottom of the brain that connects major arteries, circulates blood from the front of the brain to the back and helps the arterial systems communicate with one another.

Lobes Of The Brain And What They Control

human biology

Each brain hemisphere has four sections, called lobes: frontal, parietal, temporal and occipital. Each lobe controls specific functions.

  • Frontal lobe. The largest lobe of the brain, located in the front of the head, the frontal lobe is involved in personality characteristics, decision-making and movement. Recognition of smell usually involves parts of the frontal lobe. The frontal lobe contains Brocas area, which is associated with speech ability.
  • Parietal lobe. The middle part of the brain, the parietal lobe helps a person identify objects and understand spatial relationships . The parietal lobe is also involved in interpreting pain and touch in the body. The parietal lobe houses Wernickes area, which helps the brain understand spoken language.
  • Occipital lobe. The occipital lobe is the back part of the brain that is involved with vision.
  • Temporal lobe. The sides of the brain, temporal lobes are involved in short-term memory, speech, musical rhythm and some degree of smell recognition.

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The Eyes Are Windows Into The Brain

The eyes are a window into the workings of the brain. Many studies show that eye movements are closely linked to cognitive processes such as attention, memory, and decision-making. Eye movements not only reflect certain aspects of brain function, providing information about our thoughts and desires to others, but might also influence and actively participate in them.

The eyes also provide a glimpse into the aging and diseased brain. We now know that changes in eye movements accompany the changes that occur in the brain as a result of both normal aging and neurodegeneration. Eye movements may therefore prove to be important indicators of these processes, and there is growing interest in using them as a marker for early signs of conditions such as Alzheimers and Parkinsons diseases. Though the research is still in the early stages, it suggests that eye-tracking technology might eventually be useful in diagnosing such diseases.

Scanning the field

There are four basic types of eye movements. Vestibulo-ocular movements are reflexes that stabilize our eyes relative to the outside world to compensate for head movements vergence movements simultaneously rotate the eyes in opposite directions to align the fovea of each eye to a near or distant object and smooth pursuit movements are slow tracking moves that keep a moving object on the fovea.

Neurodegenerative diseases

Picking up the slack?

Structure And Function Of The Eyes

, MD, Mayo Clinic College of Medicine and Science

The structures and functions of the eyes are complex. Each eye constantly adjusts the amount of light it lets in, focuses on objects near and far, and produces continuous images that are instantly transmitted to the brain.

The orbit is the bony cavity that contains the eyeball, muscles, nerves, and blood vessels, as well as the structures that produce and drain tears. Each orbit is a pear-shaped structure that is formed by several bones.

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Causes Of Neurological Vision Loss

  • stroke or brain attack, where part of the brain is damaged by a haemorrhage or blockage in a blood vessel of the brain
  • traumatic brain injury for example, after a car accident or fall
  • infection, such as meningitis or cytomegalovirus
  • lack of oxygen, such as near-drowning or a heart attack, which can interrupt the flow of blood to the brain
  • disease, such as a brain tumour or multiple sclerosis.

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Why Do We Need To Move Our Eyes

The Visual System: How Your Eyes Work

One surprising fact about human vision is that, although the world appears uniformly clear to us, the clarity of the visual information we gather is not the same in all the parts of the eye. You can observe this yourself. First, stare at the purple circle in Figure 1. It is easy to read both the letters and the numbers surrounding the circle without moving your eyes. Now stare at the blue square. You can see the purple circle in the corner of your vision, but you can probably no longer read the numbers and letters around it. The blurry parts of your vision, where you can only gather limited information, are called the periphery . The clearest spot at the very center of your visual field is called the fovea . The fovea is located at the center of an important inner layer of the eyes called the retina. One reason that the retina is so important to vision is because it is made up of special cells called photoreceptors.

  • Figure 2 – The parts of the eye are shown here, viewed from the side.
  • Light first passes through the corneathe clear dome at the front of your eyeand then goes through the pupil, a dark opening in the middle of the iris. The lens then focuses the light on the retina as it passes through the inner section of the eye called the vitreous chamber. The fovea is a small area at the center of the retina where there are many special cells called cones that help you see clearly.

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Knowing The Different Parts Of The Eye Can Help You Understand How You See And What You Can Do To Help Keep The Eye Functioning Properly

The eye is one of the most complex parts of the body. The different parts of the eye allow the body to take in light and perceive objects around us in the proper color, detail and depth. This allows people to make more informed decisions about their environment. If a portion of the eye becomes damaged, you may not be able to see effectively, or lose your vision all together. What are the parts of the eye? Which part is not functioning properly when we suffer different vision problems like myopia and glaucoma? Which part produces tears?

How Your Eyes Betray Your Thoughts

A series of recent studies suggest that eye movements may both reflect and influence the workings of the brain

According to the old saying, the eyes are windows into the soul, revealing deep emotions that we might otherwise want to hide. Although modern science precludes the existence of the soul, it does suggest that there is a kernel of truth in this saying: it turns out the eyes not only reflect what is happening in the brain but may also influence how we remember things and make decisions.

Our eyes are constantly moving, and while some of those movements are under conscious control, many of them occur subconsciously. When we read, for instance, we make a series of very quick eye movements called saccades that fixate rapidly on one word after another. When we enter a room, we make larger sweeping saccades as we gaze around. Then there are the small, involuntary eye movements we make as we walk, to compensate for the movement of our head and stabilise our view of the world. And, of course, our eyes dart around during the rapid eye movement phase of sleep.

What is now becoming clear is that some of our eye movements may actually reveal our thought process.

Watching the eyes can even help predict what number a person has in mind. Tobias Loetscher and his colleagues at the University of Zurich recruited 12 volunteers and tracked their eye movements while they reeled off a list of 40 numbers.

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Left Hemisphere Vs Right Hemisphere Stroke

Along with different lobes and structures, the brain is alsodivided into two halves, called hemispheres.

Aside from the different areas of the brain that can beaffected by stroke, its also helpful to look at difference between the twohemispheres.

Generally speaking, the left hemisphere controls languageand logical reasoning while the right hemisphere is believed to control creativityand object recognition. This is why language difficulties after stroke areoften associated with left hemispherestrokes.

Furthermore, each hemisphere controls movement on the opposite side of the body. Usually, a left hemisphere stroke will cause motor impairments on the right side of the body while a right hemisphere stroke will likely impair the left side of the body.

When stroke impacts both hemispheres, its possible tosustain motor impairments on both sides of the body.

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How Do Eyes Work


The images we see are made up of light reflected from the objects we look at. This light enters the eye through the cornea, which acts like a window at the front of the eye. The amount of light entering the eye is controlled by the pupil, which is surrounded by the iris the coloured part of the eye.

Because the front part of the eye is curved, it bends the light, creating an upside down image on the retina. The brain eventually turns the image the right way up.

The retina is a complex part of the eye, and its job is to turn light into signals about images that the brain can understand. Only the very back of it is light sensitive: this part of the retina is roughly the area of a 10p coin, and is packed with photosensitive cells called rods and cones.

Cones are the cells responsible for daylight vision. There are three kinds, each responding to a different wavelength of light: red, green and blue. The cones enable us to see images in colour and detail. Rods are responsible for night vision. They are sensitive to light but not to colour. In darkness, the cones do not function at all.

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The Parietal And Temporal Lobes

We cant talk about the occipital lobe without giving a little credit to these two. While the occipital lobe carries most of the visual burden, its the parietal and temporal lobes that help us make sense of what were seeing.

The parietal lobe plays a big role in visuospatial cognition, our ability to recognize and adapt to the physical space around us. This includes abilities like depth perception, navigation and movement.

When you want to change the channel on TV, youre first using the occipital lobe to see the remote. But the parietal lobes visuospatial recognition is used to gauge how much distance is between you and the remote an important detail once you decide to reach for it.

The temporal lobe controls memory it assigns meaning to the images we see. After the occipital lobe registers the image of the TV remote, structures in the temporal lobe subconsciously remind us that the remote is used to change the channel, that it needs to be pointed at the TV, and which button we need to press to get to the channel were seeking.

The frontal lobe is usually not considered to be directly involved with vision, but scientists dont think it should be left out completely. According to the Georgia Institute of Technology, new research actually suggests it might play a role in vision after all.

Biometric Identification And Diagnosis Of Disease

The bifurcations and other physical characteristics of the inner retinal vascular network are known to vary among individuals, and these individual variances have been used for biometric identification and for early detection of the onset of disease. The mapping of vascular bifurcations is one of the basic steps in biometric identification. Results of such analyses of retinal blood vessel structure can be evaluated against the ground truth data of vascular bifurcations of retinal fundus images that are obtained from the DRIVE dataset. In addition, the classes of vessels of the DRIVE dataset have also been identified, and an automated method for accurate extraction of these bifurcations is also available. Changes in retinal blood circulation are seen with aging and exposure to air pollution, and may indicate cardiovascular diseases such as hypertension and atherosclerosis. Determining the equivalent width of arterioles and venules near the optic disc is also a widely used technique to identify cardiovascular risks.

The retina translates an optical image into neural impulses starting with the patterned excitation of the colour-sensitive pigments of its rods and cones, the retina’s . The excitation is processed by the neural system and various parts of the brain working in parallel to form a representation of the external environment in the brain.

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What Part Of The Brain Is Responsible For Vision

As soon as the information passes from the optic nerve to the remainder of the brain, it is sent to the occipital lobe, where vision is processed. The occipital lobe is located in the back of the brain, above the cerebellum, and forms the center of the visual perception system, according to the Centre for Neuro Skills. Each hemisphere has its own occipital lobe therefore, each occipital lobe processes the information sent to that particular hemisphere. The occipital lobe controls how an individual views sight, so damage to this brain section can result in visual field cuts, and problems identifying color or movement of a things.

Visual Cortex

The last part of the brain associated with vision is the visual cortex, where sensory and motor info is incorporated with vision. The Canadian Institutes of Health Research states that several visual pathways are included. For instance, the ventral visual path controls how an individual identifies items, while the dorsal visual path manages an individuals visual-motor action to things. To puts it simply, the visual cortex enables you to understand that youre taking a look at a plate, for example, and then permits you to choose it up.

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