Posts tagged vision
Articles and news from the latest research reports.
Simple eye test could diagnose Alzheimer’s
The researchers from Lancaster University have found that those with the degenerative brain disease have difficulty with one particular test. They also found that the inability to carry out the tests in those who had already been diagnosed with Alzheimer’s was linked to lower memory function.
Photo: ALAMY
Dr Trevor Crawford said the latest results were potentially exciting. They showed, for the first time, a physical connection with the memory impairment that so often is the first noticeable symptom in Alzheimer’s.
Dr Crawford, of the department of Psychology and the Centre for Ageing Research, Lancaster University, said: “The diagnosis of Alzheimer’s disease is currently heavily dependent on the results of a series of lengthy neuropsychological tests.
"However, patients with a dementia often find that these tests are difficult to complete due to a lack of clear understanding and lapse in their attention or motivation.
"Over the last 10 years, researchers in laboratories around the world have been working on an alternative approach based on the brain’s control of the movements of the eye as a tool for investigating cognitive abilities, such as attention, cognitive inhibition and memory."
During the study, 18 patients with Alzheimer’s disease, 25 patients with Parkinson’s disease, 17 healthy young people and 18 healthy older people were asked to follow the movements of light on a computer monitor. In some instances they were asked to look away from the light. Detailed eye–tracking measurements showed stark contrasts in results.
Patients with Alzheimer’s made errors on the task when they were asked to look away from the light. They were unable correct those errors, despite being able to respond normally when they were asked to look towards the light.
These uncorrected errors were 10 times more frequent in the Alzheimers’ patients than the control groups. Researchers also measured memory function among those Alzheimer’s patients who found the test difficult and were able to show a clear correlation with lower memory function. Dr Crawford added: “The light tracking test could play a vital role in the diagnosis of Alzheimer’s.”
(Source: telegraph.co.uk)
Blindsight: Animals That See without Eyes
Recent insights into how animals see without eyes reveal that vision and light-detection are older and more widespread than biologists previously realized
All vertebrates’ eyes emerge from a single group of cells, called the eye field, located in the middle of the brain. The eye field cells evaginate to form two optic vesicles, which eventually give rise to two retinas, one on either side of the brain.
Eyes Emerge
Top image: In a ~5 somites embryo, eye field cells are stained red, and forebrain cells are outlined in green (upper left). A few hours later, in a ~10 somites embryo, the eye field (green) separates into two optic vesicles. At the same embryonic stage, the dorsal telencephalon, which sits atop the evaginating eyes, is labeled blue (bottom left). In both of these images, a midline positioned cross outlines the apical surface of the optic vesicles and the ventricular space. The animation follows the development of this same surface as the eyes emerge from the brain.
Sunrise in the Eye
Bottom image: Once the basic shape of the eye is specified, cells within the optic cup differentiate, populating the retina with neurons that sense light and refine the visual information before it is transmitted to the brain. In fish and amphibia, retinal stem cells are maintained throughout the animal’s lifetime in a stem cell niche located adjacent to the lens (yellow). Here in situ hybridization of a zebrafish eye (from a ~ 3-day-old larva) reveals gene expression patterns that distinguish retinal stem cells (red) from the cells that are becoming neurons (purple). By comparing gene expression patterns within the retinal stem cell niche in normal and mutant eyes, we gain insight into how stem cells turn into neurons.
(Source: cell.com)
The stalked eyes of mantis shrimp species that live in shallow water can have up to 16 kinds of photoreceptor cells, 12 of which are specialized for different colors. People make do with four kinds, three of which pick up colors.
Hanne Thoen of the University of Queensland in Brisbane, Australia, tested the color vision of mantis shrimp by training them to scoot out of their burrows toward a pair of optical fibers and punch at the one glowing a particular color. As she narrowed the color gap between the two fibers, she could tell when the animals no longer discerned a difference.
So far, Thoen has tested her mantis shrimp on six target colors ranging from a 425-nanometer purple to a 628-nanometer red. If the animals perform just as poorly at distinguishing colors in other wavelengths, then mantis shrimp may be using some unknown system of color perception.
People and other animals studied so far distinguish colors through brainpower by interpreting competing activity in different kinds of light-receptor cells. Instead of doing such fancy brainwork, mantis shrimp may just rely on what a particular specialized cell responds to strongly. Wavelengths that tickle the purple-sensitive cells may be just plain purple regardless of whether they’re more toward the blue or the ultraviolet.
To find out how mice use their high-resolution ganglion, a team from Harvard attached a tiny camera to a rat volunteer and then watched to see what sorts of things it focused on. Next, they played the video back directly onto the retinas of several test mice while simultaneously monitoring neural cell activity. In so doing, they found that the high-resolution cells sat mostly quiet, doing nothing.
When silhouettes of birds were projected overhead, the waiting ended as the ganglia sprang into action, interpreting every movement. This shows, the researchers say, that the high-resolution neuron groups in mice retinas serve not as interpreters of everyday life, but as highly specific predator detectors. More specifically they found the nerves reacted when the birds were in their center of view, meaning close and ready to snatch them up. Sadly, they also found that the nerves quit firing once the birds came close enough, indicating the mice were doomed.
An Artificial Retina with the Capacity to Restore Normal Vision
Two researchers at Weill Cornell Medical College have deciphered a mouse’s retina’s neural code and coupled this information to a novel prosthetic device to restore sight to blind mice. The researchers say they have also cracked the code for a monkey retina — which is essentially identical to that of a human — and hope to quickly design and test a device that blind humans can use.
The breakthrough, reported in the Proceedings of the National Academy of Sciences (PNAS), signals a remarkable advance in longstanding efforts to restore vision. Current prosthetics provide blind users with spots and edges of light to help them navigate. This novel device provides the code to restore normal vision. The code is so accurate that it can allow facial features to be discerned and allow animals to track moving images.
(Image credit: Frank Müller, Institute of Complex Systems)
Researchers from the Senckenberg Research Institute in Frankfurt have revealed one of the oddest spiders ever discovered. The Sinopoda scurion is the first eyeless huntsman spider in the world.
'I found the spider in a cave in Laos, around 100 kilometres away from the famous Xe Bang Fai cave,' said Peter Jäger, head of the arachnology section at the Senckenberg Research Institute in Frankfurt. 'We already knew of spiders of this genus from other caves, but they always had eyes and complete pigmentation.
The team believe the regression of the eyes is attributable to living permanently without daylight.
(Source: Daily Mail)
Today, neuroscientists believe that your eye doesn’t see color at all — your brain creates it and constructs it through neural processes. Different features including color, shape, location, and velocity are picked up by different regions of the brain and then integrated into a holistic perception of an object.
Disney researchers add sense of touch to augmented reality applications
Technology developed by Disney Research, Pittsburgh, makes it possible to change the feel of real-world surfaces and objects, including touch-screens, walls, furniture, wooden or plastic objects, without requiring users to wear special gloves or use force-feedback devices. Surfaces are not altered with actuators and require little if any instrumentation.
Instead, Disney researchers employ a newly discovered physical phenomenon called reverse electrovibration to create the illusion of changing textures as the user’s fingers sweep across a surface. A weak electrical signal, which can be applied imperceptibly anywhere on the user’s body, creates an oscillating electrical field around the user’s fingers that is responsible for the tactile feedback.
The technology, called REVEL, could be used to create “please touch” museum displays, add haptic feedback to games, apply texture to projected images on surfaces of any size and shape, provide customized directions on walls for people with visual disabilities and enhance other applications of augmented reality.