Structure And Function Of The Third Geniculocortical Pathway In Primates.
Funder
National Health and Medical Research Council
Funding Amount
$296,777.00
Summary
Our understanding of the human visual system has been based on the idea that there are two main nerve pathways from the eye to the brain. One, called the parvocellular pathway, is for colour and detail vision, and the other, called the magnocellular pathway, is for movement perception. Damage to either pathway by disease such as glaucoma, or a lesion such as stroke, will cause specific changes in visual perception and these changes can be used to diagnose the nature of the disease or lesion. We ....Our understanding of the human visual system has been based on the idea that there are two main nerve pathways from the eye to the brain. One, called the parvocellular pathway, is for colour and detail vision, and the other, called the magnocellular pathway, is for movement perception. Damage to either pathway by disease such as glaucoma, or a lesion such as stroke, will cause specific changes in visual perception and these changes can be used to diagnose the nature of the disease or lesion. We will study a recently recognised third subdivision of the visual pathway, called the koniocellular pathway. The properties of koniocellular cells have not previously been studied in anthropoid primates, and their importance for human vision is not well understood. We will study the way that koniocellular cells respond to moving and patterned stimuli, and their connections with the cerebral cortex, in order to determine whether this pathway could contribute to aspects of normal and abnormal visual perception. We will follow up our preliminary evidence that koniocellular cells respond to visual stimuli of the type used to diagnose the early stages of eye diseases such as glaucoma. The results will give us a better understanding of the way that the nervous system processes visual information, and will clarify the basis of disturbances to normal visual function.Read moreRead less
Origin And Specificity Of Neuronal Signals For Colour Vision In Primates.
Funder
National Health and Medical Research Council
Funding Amount
$490,500.00
Summary
How do we see colours? What do colour blind people see? Although colour is one of the most important attributes of objects in the visual world, the way that colour is processed in the brain is poorly understood. The aim of this project is to study the way that nerve cells in the eye (the retina) and the visual part of the brain are specialised to transmit signals for colour perception. The visual system of humans and other primates includes nerve cells which are selective for a limited range of ....How do we see colours? What do colour blind people see? Although colour is one of the most important attributes of objects in the visual world, the way that colour is processed in the brain is poorly understood. The aim of this project is to study the way that nerve cells in the eye (the retina) and the visual part of the brain are specialised to transmit signals for colour perception. The visual system of humans and other primates includes nerve cells which are selective for a limited range of wavelengths reflected by objects in the visual world. We will study how this selectivity is generated, by examining how the colour receptors are connected within the retina to the cells which transmit nerve impulses to the brain. Between 5 and 7 percent of male humans have colour vision defects. Many objects which appear clearly different to colour-normal observers cannot be discriminated by colour-defective observers, and entry to professions such as the police and airline industry is restricted for individuals with colour vision defects. We will study the basis of reduced colour perception ability in red-green colour blindness. This will be done by measuring the responses of nerve cells in a species of primate (marmoset) in which many animals have colour vision receptors resembling those of humans with colour vision defects. We will measure the reliability with which individual neurones can transmit signals for colour vision when they receive input from such abnormal receptors. It is known that nerve cells transmit their message within the brain by means of brief electrical impulses called action potentials. In addition to studying the basis of human colour discrimination, the project also addresses one of the fundamental questions of sensory processing, by studying the reliability of the coded message carried by action potentials within the central nervous system.Read moreRead less
Myopia And Colour Vision: Potential Impact Of Colour Vision Gene Variation On Susceptibility To Myopia
Funder
National Health and Medical Research Council
Funding Amount
$227,947.00
Summary
The frequency of myopia has shown a rapid increase in recent years but the underlying cause remains largely unknown. Our recent work on severe myopia with dichromacy has indicated that some forms of myopia may arise through changes in cone visual pigments and the arrangement of cone photoreceptors in the retina which impact on the feedback loop between image formation and eye elongation. This study seeks to explore this link in detail in myopia patients that possess normal colour vision.
Network Properties Of Colour Pathways In Primates.
Funder
National Health and Medical Research Council
Funding Amount
$594,891.00
Summary
This project concerns the way in which the eye and brain work together, to enable perception of the colour, form, and movements of objects in the visual world. It is thought that these different attributes of the visual environment are signalled by several parallel nerve pathways in the visual system, but the nature of the neuronal code carried by these pathways remains poorly understood. The aim of our project is to address this basic question, in experimental studies of the intact primate visu ....This project concerns the way in which the eye and brain work together, to enable perception of the colour, form, and movements of objects in the visual world. It is thought that these different attributes of the visual environment are signalled by several parallel nerve pathways in the visual system, but the nature of the neuronal code carried by these pathways remains poorly understood. The aim of our project is to address this basic question, in experimental studies of the intact primate visual system. We plan two sets of experiments. Firstly, we will test the hypothesis that signals for both high-acuity form vision and red-green colour vision can be carried along a single neuronal pathway. We will determine whether response timing in nerve pathways provides a clue by which colour and brightness variation in the environment can be discriminated. Secondly, we will study the segregation of colour and acuity-related signals in the brain, using the method of functional optical imaging. This method, which allows nerve activity to be monitored at high resolution, over relatively large areas of the brain surface (cortex), will allow us test the hypothesis that colour signals are segregated to distinct regions of the visual cortex. These experiments address basic questions, but have application to human vision and visual dysfunction. Good acuity is essential for everyday tasks such as reading, and specific defects in colour vision are used for early detection of neurological dysfunction in diseases such as glaucoma and multiple sclerosis. Understanding the properties of neurons which underlie visual perception can thus help us to understand normal visual performance, and to develop better methods for detection and treatments for such disorders.Read moreRead less
Non-standard Receptive Fields In The Primate Visual System
Funder
National Health and Medical Research Council
Funding Amount
$392,983.00
Summary
We recently discovered that an evolutionary ancient brain pathway transmits visual signals for blue-yellow colour vision. We now plan to discover whether this pathway could also contribute to form and movement perception, and to visual functions (called blindsight) that survive damage to the main visual area of the brain. This project will contribute to understanding the effects of damage to visual pathways following stroke or brain injury, as well as to understanding normal visual function.
Characterising The Changes In Regulation Of Visual Contrast Sensitivity In Glaucoma.
Funder
National Health and Medical Research Council
Funding Amount
$337,600.00
Summary
Glaucoma is the second leading cause of blindness in developed nations. A recent study estimated the number of Australian's that will need regular visual examination in 2030 either because they have glaucoma or glaucomatous risk factors to be at least 800,000. As the ultimate aim of glaucoma treatment is to maintain vision, visual functional assessment is of paramount importance to glaucoma management . The current standard measure for the assessment of visual loss due to glaucoma is visual fiel ....Glaucoma is the second leading cause of blindness in developed nations. A recent study estimated the number of Australian's that will need regular visual examination in 2030 either because they have glaucoma or glaucomatous risk factors to be at least 800,000. As the ultimate aim of glaucoma treatment is to maintain vision, visual functional assessment is of paramount importance to glaucoma management . The current standard measure for the assessment of visual loss due to glaucoma is visual field testing. Regrettably, substantial damage to retinal ganglion cells (the primary neurons affected by glaucoma) is often present prior to the discovery of visual field loss using standard measures. Indeed studies have demonstrated that even 30-50% retinal ganglion cell loss may only manifest as a mild visual field deficit using current standard testing. This project will use novel techniques for exploring sight impairment in glaucoma, enabling a better understanding of the underlying neural damage. Our pilot work demonstrates that these methods can detect loss of sight in areas diagnosed as normal using standard visual field testing. The study will provide new technologies for the assessment of early vision loss due to glaucoma that may enable the detection of malfunction of retinal ganglion cells prior to their death. Such measures of neural malfunction are essential to establishing the efficacy of new pharmacological therapies (known as neuroprotective agents) for glaucoma aimed at keeping retinal ganglion cells alive and functioning. This project also has the potential to identify visual measures that have better capability for monitoring the progression of vision loss due to glaucoma. Early detection of glaucoma and its progression is essential so that treatment can be initiated or altered, slowing the progression of vision loss and its toll on both the individual and the community.Read moreRead less
The broad aim of this project is to understand how the eye receives visual signals and sends them to the brain. Our experimental goal is to study the structure of neural connections in a poorly understood division of the visual system, called the koniocellular pathway. The cells of the koniocellular pathway make up close to 10 percent of all projections from the eye to the brain, but their functions are almost completely unknown. The fovea is a specialised region of the retina (the nerve cells w ....The broad aim of this project is to understand how the eye receives visual signals and sends them to the brain. Our experimental goal is to study the structure of neural connections in a poorly understood division of the visual system, called the koniocellular pathway. The cells of the koniocellular pathway make up close to 10 percent of all projections from the eye to the brain, but their functions are almost completely unknown. The fovea is a specialised region of the retina (the nerve cells which line the back of the eye). It is characterised by a very high density of cone photoreceptors, and is essential for high-acuity vision. This makes the fovea the most important part of the primate retina, but the high density of nerve cells there is thought to be the reason why the fovea is especially vulnerable to disease and age-related degeneration. Our aim is to analyse, using high-resolution microscopic techniques, the connections of koniocellular-pathway cells within the retina. We specifically aim to discover whether the koniocellular pathway contributes to foveal vision. Recent work from our and other laboratories has shown that many koniocellular-pathway cells receive functional connections from short-wavelength sensitive (blue) cone photoreceptors. Thus, our study will provide new insights into the connectivity of blue-cone pathways in the fovea. Although these experiments address basic scientific questions, they can lead to improved clinical practice. Understanding the wiring diagram of the retina can inform clinical studies of conditions such as glaucoma, and helps to give a rational basis for development of treatments. For example, dysfunction in blue-cone pathways is an early sign of glaucoma, so understanding the connections of blue-cone pathways in the fovea can lead to improved methods for early detection of this leading cause of blindness.Read moreRead less
The Sydney Myopia Study: Prevalence And Risk Factors For Myopia And Other Eye Conditions In School-age Children.
Funder
National Health and Medical Research Council
Funding Amount
$596,375.00
Summary
This study aims to establish the exact extent of increasing levels of myopia in young Australians and the frequency of other treatable eye conditions such as reduced vision in one eye (amblyopia) and squint. We also aim to exam in detail, risk factors associated with myopia, such as parental myopia, living conditions and educational pressures, particularly those associated with reading and other forms of near-work. Increased understanding of factors leading to increasing myopia prevalence may en ....This study aims to establish the exact extent of increasing levels of myopia in young Australians and the frequency of other treatable eye conditions such as reduced vision in one eye (amblyopia) and squint. We also aim to exam in detail, risk factors associated with myopia, such as parental myopia, living conditions and educational pressures, particularly those associated with reading and other forms of near-work. Increased understanding of factors leading to increasing myopia prevalence may enable design of preventive strategies that could limit future increases in the ocurrence of myopia in Australia. The prevalence of myopia is increasing world-wide. In many Asian countries, it has reached epidemic proportions (80-90%) in young, educated people. In many other countries close to half the younger population is now short-sighted. Data from the Blue Mountains Eye Study and Melbourne Visual Impairment Project in older persons have suggested that the prevalence of myopia is increasing in Australia. Comparison with our recent pilot study on school children indicates that myopia prevalence has increased 2 to 3-fold in recent decades. Myopia or short-sightedness is now one of the five major causes of blindness. In countries where the prevalence of myopia is high, it is one of the top three. Myopia requires expensive optical and-or surgical correction of the refractive error for visual functioning. Unfortunately correction does not prevent the development of visual impairment and blindness from complications of myopia. Late in life, even low myopia is associated with an increased risk of both glaucoma and cataract. Myopia therefore imposes additional major health costs because of the burden of eye disease and the support costs for people affected by myopia-associated low vision or blindness. With increasing prevalence, the health care costs of myopia are likely to continue to rise in Australia.Read moreRead less