Novel Approaches To Understanding Peripheral Vision In Patients With Central Vision Loss
Funder
National Health and Medical Research Council
Funding Amount
$367,101.00
Summary
The aim of my research is to develop novel interventions that enhance the peripheral vision of patients with central vision loss, and to investigate the neural correlates of visual perception in peripheral vision in typical adults. My research will inform rehabilitation strategies that optimise the visual function of patients with partial blindness, and provide a more thorough understanding of the underlying neural mechanisms that reduce the quality of peripheral vision.
Using Contextual Effects To Test Theories Of Coding In Visual Cortex
Funder
National Health and Medical Research Council
Funding Amount
$200,500.00
Summary
The visual cortex is the main structure in the brain that processes the visual scene. Cells in the cortex respond selectively to features of the scene such as the orientation of objects, the direction they move and their brightness relative to the background. Cortical cells are arranged in a topographic map of visual space, so that nearby cells respond to light from nearby parts of the image. Recent advances have shown that cells talk to each other so a stimulus in one part of the visual field c ....The visual cortex is the main structure in the brain that processes the visual scene. Cells in the cortex respond selectively to features of the scene such as the orientation of objects, the direction they move and their brightness relative to the background. Cortical cells are arranged in a topographic map of visual space, so that nearby cells respond to light from nearby parts of the image. Recent advances have shown that cells talk to each other so a stimulus in one part of the visual field can influence the responses of cells looking at other regions. This communication between cells is important in guiding the brain to focus on areas of the visual scene that are most important, a process known as attention. An example would be that a mouse moving through the periphery of someone's vision would attract their attention away from objects elsewhere in the scene. This project is designed to study the way that cells in the visual cortex cooperate to guide attention. Attention is important because it reduces the need to process all the detail in the visual scene with the same level of accuracy, leaving more resources free to process what is important. Attention deficits are a problem for people with dyslexia, so understanding the physiological basis of attention is an important goal. As well as attention, the visual system has a range of other mechanisms to select important information from the visual scene. For example, visual adaptation tends to improve the ability to code changes in the visual scene at the expense of reducing the sensitivity of the system overall. This project will investigate the relationship between attentional and adaptive mechanisms in the visual cortex. We expect to establish the precise physiological mechanisms that drive adaptive and attentional mechanisms in the mammalian brain.Read moreRead less
Functional Anisotropies In The Processing Of Orientation And Direction-of-motion By Human Visual Cortex
Funder
National Health and Medical Research Council
Funding Amount
$366,164.00
Summary
We will study patterns of activity in the human brain to identify the cortical signature of normal visual function. The correspondences between patterns of brain activity and the structure and motion of the visual image in the normal human brain will provide data against which brain activity in a range of disorders from amblyopia to schizophrenia can be assessed.
Orientation-specific Contextual Modulation In Human Visual Cortex
Funder
National Health and Medical Research Council
Funding Amount
$290,413.00
Summary
Context has a strong infuence on our visual perception. We will study patterns of activity in the normal human brain to identify the cortical signature of contextual modulation in vision. The correspondences between patterns of brain activity and visual perception in the normal human brain will provide data against which brain activity in disorders such as schizophrenia and bipolar disorder can be assessed.
The GABAergic System In Eye Growth Control And Myopia
Funder
National Health and Medical Research Council
Funding Amount
$318,142.00
Summary
Shortsightedness (myopia) is the most common visual disorder. High myopia is associated with an increased risk of eye diseases. Current treatments do not stop myopia developing or decrease the associated risk of eye disease. The continued worsening of myopia is very concerning. A safe effective treatment that can either prevent myopia or stop its progression to extreme levels is needed. We have data showing that GABA ergic drugs modify myopia. This proposal will determine the mechanisms.
Brain Pathways Serving Conscious And Sub-conscious Vision
Funder
National Health and Medical Research Council
Funding Amount
$571,444.00
Summary
In humans and other primates the visual system comprises evolutionary new pathways (called magnocellular or M, and parvocellular or P) superimposed on evolutionary old pathways (called koniocellular or K). These parallel pathways carry visual information from the retina, through a brain centre in the thalamus called lateral geniculate nucleus (LGN), to the cerebral neocortex. Our aim is to study the role of the K pathway in visual processing.
Properties Of Human Photoreceptors Measured Using A Scanning Laser Ophthalmoscope To Illuminate And Image The Retina
Funder
National Health and Medical Research Council
Funding Amount
$352,000.00
Summary
Vision begins with the detection of light by the rod and cone photoreceptors in the retina lining the interior of the eye. Although much is already known about the way that light is detected and the signals are processed, a great deal remains to be learned. Some of the outstanding questions could be answered using modifications to a relatively new instrument called a scanning laser ophthalmoscope (SLO) which provides images of the interior of the eye. The aims of this project are to develop a mo ....Vision begins with the detection of light by the rod and cone photoreceptors in the retina lining the interior of the eye. Although much is already known about the way that light is detected and the signals are processed, a great deal remains to be learned. Some of the outstanding questions could be answered using modifications to a relatively new instrument called a scanning laser ophthalmoscope (SLO) which provides images of the interior of the eye. The aims of this project are to develop a modified SLO, which is able to measure the levels of visual pigment (rhodopsin) in the living eye, which is also able to deliver visual stimuli to the eye, and which finally is extended to use adaptive optics so that it can image and excite individual cone photoreceptors. Using this device, we will be able to measure the regeneration of visual pigment following exposures to intense illumination, to help explain the slow recovery of visual sensitivity after intense light. We will also be able to measure the electroretinogram (ERG) from localized retinal areas, to investigate how the properties of the photoreceptor cells vary across the retina. And finally we will be able not only to visualize the individual tiny cone photoreceptors, but also to stimulate them selectively, so that we can determine the responses of the different classes of cone (red-, green-, and blue-sensitive cones) in the living human eye.Read moreRead less
Functional Interactions Between Primate Cortical Areas In Tasks Involving Attention And Short-term Memory
Funder
National Health and Medical Research Council
Funding Amount
$267,280.00
Summary
To navigate and operate in the cluttered and dynamic sensory world around us, our brains need to be able to attend to specific objects or features in the environment, identify them and also know where they exist at any one instant of time, prior to performing the appropriate action. The attention, memory, decision and motor components involved in this process possibly involve a variety of cortical areas and neuronal operations. The special primate preparation we have developed permits us to eluc ....To navigate and operate in the cluttered and dynamic sensory world around us, our brains need to be able to attend to specific objects or features in the environment, identify them and also know where they exist at any one instant of time, prior to performing the appropriate action. The attention, memory, decision and motor components involved in this process possibly involve a variety of cortical areas and neuronal operations. The special primate preparation we have developed permits us to elucidate at a neuronal level many of these brain mechanisms. By recording neuronal activities in two different cortical areas simultaneously as the monkey performs a memory task that he has been trained on, we will test the following ideas: (1) A cortical region in the dorsal, parietal stream directs spatial attention by gating other visual areas to process only a selected region of the visual world (2) A region in the ventral, temporal stream directs attention to specific features in the visual world by gating earlier cortical areas (3) The parietal cortical areas that mediate intention for action hold the relevant information in working memory till it is forwarded to the more anterior premotor areas. These experiments have the potential to reveal the basic neuronal scheme that underpins functions such as attention, visual recognition and memory, which are impaired in many neurological disorders.Read moreRead less
Functional Connectivity Between Visual Cortical Areas In The Non-human Primate
Funder
National Health and Medical Research Council
Funding Amount
$387,585.00
Summary
Visual information going from the eyes to the brain is processed in different parts of the brain to extract useful information. However, to be able to select what is important from among the vast number of objects in the scene, top-down signals from higher areas need to act on incoming signals in earlier areas. This project aims to identify what sort of neural pathways are involved in this and how it is done at the cellular level.
Role Of Cortico-cortical Connections In Mediating Cerebral Cortex Plasticity: Visual Cortex Model
Funder
National Health and Medical Research Council
Funding Amount
$362,500.00
Summary
In mammals injury to the retina not only affects the neurones within the eye but also induces changes in the other parts of the brain, particularly in the visual cortex. It has been found that after retinal injury cells in the visual cortex, normally receiving an input from the injured part of the retina, now receive an input from adjacent normal retina ( ectopic receptive field ). All mammals with well developed vision have a large number of separate visual cortical areas (more than 30 in prima ....In mammals injury to the retina not only affects the neurones within the eye but also induces changes in the other parts of the brain, particularly in the visual cortex. It has been found that after retinal injury cells in the visual cortex, normally receiving an input from the injured part of the retina, now receive an input from adjacent normal retina ( ectopic receptive field ). All mammals with well developed vision have a large number of separate visual cortical areas (more than 30 in primates). These areas are arranged in a hierarchy in which it is thought that as features of the visual stimuli become more complex they are discriminated in the areas higher in the hierarchy. These higher-order areas also project back to lower-order areas. This feedback activity from the higher areas can be reversibly abolished by cooling a given area to about 10oC and then rewarming it back to its normal temperature. We will try to determine if in cats (animals with well developed vision) following damage to a small region of the retina the feedback activity from higher visual cortical areas affects the ectopic receptive fields in the lower visual cortical areas. Another possibility is that the ectopic receptive field apparent following retinal damage might depend on horizontal connections within the particular cortical area, running from normal cortex to the area of cortex affected by the lesion. We propose to test this idea by blocking reversibly (with chemical agents) transmission of these horizontal fibres and determining the characteristics of neurones in the area affected by the lesion. Understanding the role of feedback and horizontal cortico-cortical connections in establishing new ectopic receptive fields following spatially delineated damage to the retina will help us to understand the mechanisms underlying perceptual distortions and visual hallucinations which occur following retinal traumas or some age-related retinal degenerations.Read moreRead less