Bad Reflections These odd shapes, nick-named the ‘muffin’ (left) and the ‘potato’ (right), are a real test to our powers of observation. Our brains make sense of the world around us using binocular stereopsis: a process that compares what the left and right eyes see, using small differences between their viewpoints to estimate distance and depth. When looking at shiny things, however, this is much more of a challenge. Human test subjects looking at a 3-dimensional shiny muffin found its curve difficult to judge; their eyes were confused by false dips and bends in the glimmering reflections. The potato’s contours were, oddly, much easier to spot. Psychophysicists believe that when looking at highly irregular shapes, our brains decide to take binocular stereopsis with a pinch of salt and quickly search for other clues to work out shape and depth in the midst of so many brain-bending reflections. Written by John Ankers — Andrew Welchman University of Birmingham, UK Published in PNAS 110(6): 2413-2418
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Bad Reflections

These odd shapes, nick-named the ‘muffin’ (left) and the ‘potato’ (right), are a real test to our powers of observation. Our brains make sense of the world around us using binocular stereopsis: a process that compares what the left and right eyes see, using small differences between their viewpoints to estimate distance and depth. When looking at shiny things, however, this is much more of a challenge. Human test subjects looking at a 3-dimensional shiny muffin found its curve difficult to judge; their eyes were confused by false dips and bends in the glimmering reflections. The potato’s contours were, oddly, much easier to spot. Psychophysicists believe that when looking at highly irregular shapes, our brains decide to take binocular stereopsis with a pinch of salt and quickly search for other clues to work out shape and depth in the midst of so many brain-bending reflections.

Written by John Ankers

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Source: bpod.mrc.ac.uk

Eye Insights The eyes of fish grow larger throughout their lives because stem cells produce new tissue in the retina, the light-sensitive lining at the back of the eye. Humans and other mammals lack these stem cells, so the retina can neither grow nor be repaired naturally. Studies of zebrafish show that the development of stem cells in the retina is controlled by chemicals from nerve cells nearby. This research may lead to a better understanding of degenerative diseases of the eyes and nervous system in humans and the causes of cancer, which can occur when stem cells go out of control. Pictured is a cross-section of a zebrafish eye. The ring stained green with the dark centre is the lens, with the retina appearing as a semi-circle around it. Stem cells are concentrated in the regions at either end of the red-stained arcs of nerve connecting tissue. Written by Mick Warwicker — Kara Cerveny Zebrafish Research, UCL, London
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Eye Insights

The eyes of fish grow larger throughout their lives because stem cells produce new tissue in the retina, the light-sensitive lining at the back of the eye. Humans and other mammals lack these stem cells, so the retina can neither grow nor be repaired naturally. Studies of zebrafish show that the development of stem cells in the retina is controlled by chemicals from nerve cells nearby. This research may lead to a better understanding of degenerative diseases of the eyes and nervous system in humans and the causes of cancer, which can occur when stem cells go out of control. Pictured is a cross-section of a zebrafish eye. The ring stained green with the dark centre is the lens, with the retina appearing as a semi-circle around it. Stem cells are concentrated in the regions at either end of the red-stained arcs of nerve connecting tissue.

Written by Mick Warwicker

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Source: bpod.mrc.ac.uk

Neglected Eyes By definition, neglected diseases are overlooked. Their effects are not often deadly, but can still wreak havoc among an estimated billion people in the world’s poorest populations. Trachoma, a bacterial infection that leads to blindness, is a prime example. Illustrated by this map, in which country size relates to numbers of trachoma cases, the overwhelming burden of the disease falls on Africa and South-East Asia. And, although it causes no large, media-attracting outbreaks, the disease nonetheless takes a dramatic toll. Over 40 million people need treatment, as the roughening of the eyelids and in-growing of their lashes slowly but steadily destroys their eyes. But it doesn’t have to be this way. Treatments costing as little as 50p would go a long way to eliminate the disease, and prevent further growth of the group of more than one million people who have already lost their sight because of the disease. Written by Jan Piotrowski — Copyright SASI Group (University of Sheffield) and Mark Newman (University of Michigan)
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Neglected Eyes

By definition, neglected diseases are overlooked. Their effects are not often deadly, but can still wreak havoc among an estimated billion people in the world’s poorest populations. Trachoma, a bacterial infection that leads to blindness, is a prime example. Illustrated by this map, in which country size relates to numbers of trachoma cases, the overwhelming burden of the disease falls on Africa and South-East Asia. And, although it causes no large, media-attracting outbreaks, the disease nonetheless takes a dramatic toll. Over 40 million people need treatment, as the roughening of the eyelids and in-growing of their lashes slowly but steadily destroys their eyes. But it doesn’t have to be this way. Treatments costing as little as 50p would go a long way to eliminate the disease, and prevent further growth of the group of more than one million people who have already lost their sight because of the disease.

Written by Jan Piotrowski

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Source: bpod.mrc.ac.uk

In-flight Sight This section through the brain of a fruit fly, Drosophila, shows neurons [nerve cells] firing into action in preparation for flight. Yet something odd is going on – the neurons lit up at the centre of the brain (stained in green with their nuclei stained red) are actually sending messages to the optic lobes (ball-shaped areas on the left and right) where vision is controlled. These special neurons (known as octopamine neurons) boost the fly’s sight prior to take-off, aiding its panoramic view of the terrain whilst soaring high above the ground. Each neuron is 5,000 times thinner than an electrical wire and transmits these signals in a fraction of a second. Speedy ‘re-wiring’ of neurons occurs inside mammalian brains, too – the visual senses of the mouse brain are heightened during movement, a handy trick when you’re on the hunt for a meal, or trying to avoid becoming one. Written by John Ankers — Marie Suver, California Institute of Technology, USA Michael H. Dickinson, University of Washington, USA Copyright Elsevier 2012 Published in Current Biology 22(24): 2294-2303
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In-flight Sight

This section through the brain of a fruit fly, Drosophila, shows neurons [nerve cells] firing into action in preparation for flight. Yet something odd is going on – the neurons lit up at the centre of the brain (stained in green with their nuclei stained red) are actually sending messages to the optic lobes (ball-shaped areas on the left and right) where vision is controlled. These special neurons (known as octopamine neurons) boost the fly’s sight prior to take-off, aiding its panoramic view of the terrain whilst soaring high above the ground. Each neuron is 5,000 times thinner than an electrical wire and transmits these signals in a fraction of a second. Speedy ‘re-wiring’ of neurons occurs inside mammalian brains, too – the visual senses of the mouse brain are heightened during movement, a handy trick when you’re on the hunt for a meal, or trying to avoid becoming one.

Written by John Ankers

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Source: bpod.mrc.ac.uk

Shady Behaviour As our eyes scan this page, the cells in our retinas are firing off messages. It takes them a split-second to convert this picture – of similar cells inside the retina of a zebrafish – into electrical signals bound for the brain. A high-powered microscope was used here to zoom in on a cross-section of the fish’s retina, highlighting the contours of different layers of cells. The sensitive photoreceptors (the layer of larger, bulky cells on the left) gather light from the outside world, converting it into an electrical signal that penetrates deeper into the retinal tissue (the layers of cells on the right). Meanwhile, the black-coloured, inky pigment cells absorb any excess light, protecting the photoreceptors from damage. Our eyes, it appears, have their own internal pair of sunglasses. Written by John Ankers — Rachel Macdonald and Steve Wilson UCL, UK
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Shady Behaviour

As our eyes scan this page, the cells in our retinas are firing off messages. It takes them a split-second to convert this picture – of similar cells inside the retina of a zebrafish – into electrical signals bound for the brain. A high-powered microscope was used here to zoom in on a cross-section of the fish’s retina, highlighting the contours of different layers of cells. The sensitive photoreceptors (the layer of larger, bulky cells on the left) gather light from the outside world, converting it into an electrical signal that penetrates deeper into the retinal tissue (the layers of cells on the right). Meanwhile, the black-coloured, inky pigment cells absorb any excess light, protecting the photoreceptors from damage. Our eyes, it appears, have their own internal pair of sunglasses.

Written by John Ankers

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Source: bpod.mrc.ac.uk

Seeing Blind The human eye can distinguish about ten million colours thanks to the light-sensitive lining at the back of our eye. Containing millions of cells, called rods and cones, the retina (pictured flattened out from a mouse eye) absorbs light and transmits this visual information to the brain. Also within this specialised layer are thousands of melanopsin retinal ganglion cells (stained purple) that control our subconscious responses to light, such as the shrinking and expanding of our pupils. Scientists reveal that these cells also provide unexpected amounts of visual information to the brain during conscious vision. In mice completely lacking rods and cones, the contribution of these ganglion cells was enough to prompt responses to light. This discovery may help to solve the mystery of why some people who lose rods and cones as a result of eye disease can still consciously detect the presence of light even when blind. Written by Lux Fatimathas — Robert Lucas, University of Manchester, UK Satchidananda Panda, Salk Institute for Biological Studies, USA Originally published under Creative Commons (CC-BY 2.0) Published in PLoS Biology 8(12): e1000558
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Seeing Blind

The human eye can distinguish about ten million colours thanks to the light-sensitive lining at the back of our eye. Containing millions of cells, called rods and cones, the retina (pictured flattened out from a mouse eye) absorbs light and transmits this visual information to the brain. Also within this specialised layer are thousands of melanopsin retinal ganglion cells (stained purple) that control our subconscious responses to light, such as the shrinking and expanding of our pupils. Scientists reveal that these cells also provide unexpected amounts of visual information to the brain during conscious vision. In mice completely lacking rods and cones, the contribution of these ganglion cells was enough to prompt responses to light. This discovery may help to solve the mystery of why some people who lose rods and cones as a result of eye disease can still consciously detect the presence of light even when blind.

Written by Lux Fatimathas

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Source: bpod.mrc.ac.uk