The Signals Of Nerve Cells That Provide The Capacity For Sight
Funder
National Health and Medical Research Council
Funding Amount
$385,115.00
Summary
Sight relies on the signals of nerve cells in the brain, but we know little about the way in which nerve cells support this, or why in some people sight is diminished. In this work we will measure the signals of nerve cells in the visual pathway to gain knowledge of these processes: we will make measurements in normal animals and in those that suffer from brain disorders. Our work will provide a scientific basis for the diagnosis and treatment of these disorders.
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
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
Neural Mechanisms That Limit The Visual Sensitivity Of Primates
Funder
National Health and Medical Research Council
Funding Amount
$379,400.00
Summary
This project concerns the way nerve cells in the brain enable the detection and perception of objects in the visual world. It is thought that nerve cells early in the visual pathway signal the presence or absence of light in a small part of the visual field, 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 will conduct two sets of exper ....This project concerns the way nerve cells in the brain enable the detection and perception of objects in the visual world. It is thought that nerve cells early in the visual pathway signal the presence or absence of light in a small part of the visual field, 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 will conduct two sets of experiments. Firstly, we will test the hypothesis that nerve cells in the early visual system are sensitive to only a small part of the visual field. We will determine whether the signals of pre-cortical nerve cells are dependant on spatial context. Secondly we wll study the signals of several nerve cells simultaneously using multiple electrodes. We will determine if the signals of many nerve cells are required to detect small visual stimuli like those used in perimetry. 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 defects in visual sensitivity are used for early detection of neurological dysfunction in diseases such as glaucoma and macular degeneration. Understanding the properties of neurons which underlie visual perception can thus help us to understand normal visual performance, and how this changes in partial sight. This can help 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.