Part : The Ear And The Brain
To understand how clients will respond to sound systems, and tohelp protect your hearing, consider the intricate and surprisingauditory pathways.
COMPARE FOR A MOMENT THE EYE and the ear. There is no question thatthe eye is more sensitive to the human environment. The dark-adaptedeye needs only 0.5 attojoules of energy at its retina to perceivelight. The ear needs about 100 joules of energy 20 orders ofmagnitude more at the eardrum to perceive a sound.
The dynamic range of the two sensory organs is also dramaticallydifferent, but the ear is much more versatile. The range from thethreshold of perception to the threshold of damage is about 90 dB inthe case of the eye. Thats an amazing dynamic range by any estimation.The dynamic range of hearing in an audiologically normal person is fiveorders of magnitude greater: 140 dB.
Consider also the frequency response of seeing and hearing. This isthe range of frequencies over which the sensory organ operates. The eyecan sense light ranging in frequency from infrared to ultraviolet .This is a range of about 0.7 octaves. The ear of a young person ofmoderate tastes, on the other hand, can hear sounds from around 20 Hzto 20 kHz, 10 octaves.
Both the eye and the ear are connected to the brain, and the sensorymechanisms of both interact in intimate and complex ways with it. Wederive more information about the world than the sensory organs alonecan provide. Consider this analogy from Albert Bregman:
GROSSANATOMY OF THE EAR
How The Eyes Communicate With The Brain
When we decide to look at something, a brainstem structure called the pons is called into action. It controls eye movement, constantly telling our eye muscles to move toward the correct stimulus of light .
When light enters the eye through the pupil, it strikes in the retina called rods and cones. Rod cells are responsible forperipheral vision and night vision, while cone cells react to brighter light, color and fine details.
When light hits its corresponding rod or cone, the cell activates, firing a nerve impulse through the optic nerve the middle man between the eye and the brain.
This impulse travels across countless nerve endings and eventually ends up with our pal the occipital lobe, where its processed and perceived as a visible image. This is eyesight.
Since an image isnt much help without meaning, the occipital lobe sends this visual information to the hippocampus in the temporal lobe. Here its stored as a memory.
All of this happens within the tiniest fraction of a second, allowing us to perceive the world in essentially real time.
The human brain is an incredibly complex web of neurons and synapses. And the more we understand about its mind-boggling ability to process and make sense of random collections of light, the more we can appreciate the equally complex world around us.
STILL HAVE QUESTIONS ABOUT YOUR BRAIN AND VISION? Talk to an eye doctor near you to schedule an appointment.
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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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Seven Intriguing Facts About Our Eyes And Vision
1. The image projected onto the back of our eyes is upside down. Our brain decodes this image so that we perceive it the right way up.
2. Experiments by MIT scientists show that the human brain can process and correctly identify images seen for as little as 13 milliseconds.
3. The muscles that control your eyes are the most active muscles in your body.
4. Concentrated at the outer edges of the retina, rod cells are involved in peripheral vision. They are far more sensitive to light than cone cells, which is why you can sometimes see stars out of the corner of your eye at night, but when you look straight at them they seem to disappear.
5. Human eyes are actually extremely sensitive to light – they can detect a single photon in a dark room, according to new research published in Nature Communications.
6. The ‘red eye’ effect in photos occurs when light from the flash bounces off the back of the eye, where there are lots of blood vessels in a layer called the choroid.
7. At the point where the optic nerve leaves the eye there aren’t any light receptor cells. This creates a blind spot. Most of the time we don’t see this empty, dark area though: our brain fills in the gap using information from the surrounding picture or other eye.
Seeing The Brain Through The Eyes
A neurosurgeon at the University of Cape Town is pioneering a way to diagnose a brain condition through patients eyes.
Since ancient times, the eye has been seen as a portal to the innermost secrets of the human mind and body a window to the soul. Taking a more literal approach to this metaphorical truth, Dr Llewellyn Padayachy, a paediatric neurosurgeon at the University of Cape Town has spent the past five years or so researching a novel diagnostic method that uses ultrasound and the eye as a window to the brain.
What you do as a paediatric neurosurgeon is treat a condition called hydrocephalus more than anything else, Padayachy explains. And the sad thing is, a lot of the children we treat, without a doubt, present to us much later than they should.
More often than not, the reason for this is that the children come from impoverished rural areas, where the condition would not have been picked up in a primary healthcare clinic, due to a lack of resources.
While accurate data regarding the number of hydrocephalus cases on the African continent is sparse, conservative estimates put it at some 100 000 cases annually. In the United States, it affects about one million people in every stage of life: from infants to the elderly.
Undergoing this sort of procedure is highly traumatic for any patient and even more so for babies and young children.
Journey of discovery
From rural clinics to the final frontier
Story: Nadia Krige. Photo: Pexels, Pixabay.
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What Are The Optic Nerve Branches
Each optic nerve has branches that travel to your brain or join with other fibers. When the two optic nerves cross at the optic chiasm:
- Half of the nerve fibers from your left eye continue to the left side of your brain.
- Half of your right eyes nerve fibers connect to the right side of your brain.
- The remaining nerve fibers join together. Your brain receives signals from both eyes at the same time to create a cohesive visual image .
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.
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You See Black Spots In Your Vision
Black spots in your vision, as well as blurriness, may be a sign of an eye condition known as macular degeneration. So these are two symptoms you don’t want to keep to yourself. “A diagnosis of macular degeneration early on can help patients prevent the advancement of the disease,”Dr. Jean Keamy, board-certified ophthalmologist, tells Bustle. “Treatment options for macular degeneration include vitamin therapy, lifestyle changes, and sometimes injections into the eye.”
You Have A Sensitivity To Light
Itâs natural for your vision to get cloudier as you age. This is what’s known as a cataract, and it can cause a sensitivity to light along with clouded or blurred vision, and a need to frequently change your eyeglasses prescription. Cataracts won’t go away on their own, so make sure you tell your eye doctor if you notice any of these signs.
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What Part Of The Brain Controls Vision
The brain consists of four main segments called lobes. The frontal lobe up front, the parietal lobe on top, the temporal lobe on bottom and the occipital lobe pulling up the rear. All of our senses, thoughts and actions start in one of these lobes.
Most visual functions are controlled in the occipital lobe, a small section of the brain near the back of the skull. But processing eyesight is no simple task, so other parts of the brain have to pitch in too.
You Have Persistent Discomfort
Eye pain for no reason is one thing. But if you experience eye discomfort after, say, drilling or hammering, it could be cause for concern. Get yourself checked by a doc to make sure there isnât something in your eye that could lead to an infection, as that’s definitely not something you want getting out of control.
While not all eye problems are a sign of something super serious, they still shouldn’t be ignored. If you feel like your vision is worsening, or if you’re experiencing any of the annoying symptoms above, be sure to make an appointment with your eye doctor.
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Ways Of Manipulating Hemispheric Dominance
|Any physical stimulus of the left hand side of the body is going to increase activity in your right brain hemisphere so a firm pinch on the left leg will encourage a larger right-brain contribution to the activity at hand. Similarly twisting a finger on the right hand is likely to produce an increase in the left hemisphere’s involvement in what is going on. Note that if the stimulus becomes too painful to bear, the brain will tend to move away from the source and will produce the opposite movement of a gentler, bearable stimulus.|
Part : The Eye And The Brain
The display of information must meet the needs of the eye. Someof these needs come from the eye itself, and some come from thebrain.
THE EYE, AS WE ALL KNOW, IS A LIGHT-sensitive organ of vision thatpermits us to discriminate among minute variations of shape, color,brightness and distance. Every successful visual display must beadapted to the peculiar characteristics of the eye, and everyoneworking with video needs to understand the sensory organ being served.The eyes are truly our windows onto the world, but how much do you knowof their operation and working? Many of us have a certain ommatophobia,a fear of the eye, or anyway a fear of looking too closely into it.
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What You Probably Didnt Know About How Your Eyes See
Â«What the eye doesnât see and the mind doesnât know, doesnât exist,Â» said D. H. Lawrence. And he was right, because vision is the result of teamwork between the eyes and the brain, which together create a complete and complex picture of the world around us. This is the latest thing that neurobiologists, physicists and optical experts around the world have learned about how we see.
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.
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New Bionic Eyes Beam Pictures Right Into Your Brain
This camera will send wireless signals to a chip surgically implanted in the brain.
Australian researchers from Monash University are developing new “bionic eyes” that don’t rely on the organic ocular system to restore sight to the blind. Rather than using a retinal implant that stimulates the optic nerves within the eye, the new device essentially amounts to a pair of glasses with a mounted camera that is connected directly to the brain. A blind Australian is scheduled to be the first to receive the new device next year.
The system requires implanting 11 small tiles into parts of the brain that receive and process signals related to vision. Each tile will contain 43 electrodes that can stimulate the brain with electrical signals to create dots of light similar to pixels, adding up to a total of just under 500 pixels of vision. The end result won’t be anything like the 1 to 2 million pixels a human eye can produce, but it could restore a semblance of vision to people whose retinas have been damaged beyond use.
Images that the camera receives are first routed through a digital processor on the side of the glasses. The processor breaks down the image and extracts the relevant information before wirelessly transmitting signals to the brain tiles. The result should be a crude image, which lead researcher Arthur Lowery compares to 1920s images produced by John Baird’s “televisor.”
Use It Or Lose It: Visual Activity Regenerates Neural Connections Between Eye And Brain
NIH-funded mouse study is first to show visual stimulation helps re-wire visual system and partially restores sight.
A study in mice funded by the National Institutes of Health shows for the first time that high-contrast visual stimulation can help damaged retinal neurons regrow optic nerve fibers, otherwise known as retinal ganglion cell axons. In combination with chemically induced neural stimulation, axons grew further than in strategies tried previously. Treated mice partially regained visual function. The study also demonstrates that adult regenerated central nervous system axons are capable of navigating to correct targets in the brain. The research was funded through the National Eye Institute , a part of NIH.
Reconnecting neurons in the visual system is one of the biggest challenges to developing regenerative therapies for blinding eye diseases like glaucoma, said NEI Director Paul A. Sieving, M.D., Ph.D. This research shows that mammals have a greater capacity for central nervous system regeneration than previously known.
The researchers induced optic nerve damage in mice using forceps to crush the optic nerve of one eye just behind the eyeball. The mice were then placed in a chamber several hours a day for three weeks where they viewed high-contrast imagesessentially changing patterns of black lines. The mice had modest but significant axonal regrowth compared to control mice that did not receive the high-contrast visual stimulation.
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A Computer In Your Head
Eric H. Chudler, Ph.D.Originally published in ODYSSEY magazine, 10:6-7, 2001 , Cobblestone Publishing Co.
What has billions of individual pieces, trillions of connections,weighs about 1.4 kilograms, and works on electrochemical energy? If youguessed a minicomputer, you’re wrong. If you guessed the human brain,you’re correct! The human brain: a mass of white-pink tissue that allowsyou to ride a bike, read a book, laugh at a joke, and remember yourfriend’s phone number. And that’s just for starters. Your brain controlsyour emotions, appetite, sleep, heart rate, and breathing. Your brain iswho you are and everything you will be.
The amazing brain has been compared to many different objects anddevices — from a spider web to a clock to a telephone switchboard.Nowadays, people like to compare it to a computer. Is your brain reallylike the metal box that hums on your desk? Let’s look at the similaritiesand differences between the two.