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Our work
has important applications in the development of tools and technologies
for robotics and medicine.The group is part of the campus wide
Centre
for Visual Sciences and the ARC Centre for Excellence in Vision Science.
Current Research
Visual Processing in Mammalian Brains
My laboratory studies the neural basis of visual perception by recording single cell activity in cat and monkey cortex and by measuring human reactions to visual stimulation. Topics include the neural basis of motion processing and adaptation to contrast and motion. In behaving monkeys we record neural activity during eye movements and relate the findings to perception. Laboratory webpage.
Bio-inspired principles of flight control
Our laboratory investigates the processes and techniques involved in insect vision. All insects are limited by severe size and weight restrictions, which means that they cannot carry large brains or highly complex visual systems. This means that they often employ simple optical or neural 'tricks' to achieve complex behavioural tasks. We are interested in investigating these 'tricks' with the intention of applying the principles of insect vision to real world engineering type problems. Our main study animal is the dragonfly, which is capable of amazingly acrobatic flights at very high speed. We are especially interested in how the three simples eyes of the dragonfly (the ocelli) may contribute to their acrobatic abilities.
Neuroethology of Visual Information Processing and Colour Vision
The aim of our research is to explore the relationship between an animals' information processing
requirements and the design of their visual system. We are especially interested in how these
factors constrain and shape their decision making, as seen in their behaviour. We work with a range
of study animals such as fiddler crabs and marsupials.
Human Brain Dynamics
We are studying interactions in the hierarchy of cortical areas using multimodal neuroimaging techniques. This includes the multifocal mapping of activity in early cortical areas combining responses recorded with electroencephalography and magnetoencephalography with spatial constraints obtained with functional magnetic resonance imaging, and the study of the effects of transcranial magnetic stimulation on perceptual processes.
Development of Visual Diagnostics for Eye Diseases
We are studying how the eye processes motion, size, texture,
and brightness. We are also interested in multifocal methods with
applications in neurophysiology, and objective perimetry for diseases
like glaucoma and multiple sclerosis.
Development of the Visual System
We are studying the development of the visual system using the marsupial mammal, the wallaby, as a model. The protracted and largely postnatal development of its visual system makes it an excellent alternative to common laboratory placental mammals for developmental studies. Molecular and anatomical methods are used to investigate mechanisms involved in establishing maps of the visual world in visual centres in the brain. A stereotaxic atlas of the wallaby brain is available here.
Retinal and Myopia Research
Our current major emphasis is how retinal circuits control eye growth, and hence regulate the development of short-sightedness. In human epidemiological studies, we explore environmental (education and life-style) factors that promote short-sightedness. In parallel laboratory experimentation, we explore the optical and cellular/molecular pathways that control eye growth, in an attempt to develop preventive regimes.
Foveal Development and Macular Degeneration
Signals from cone photoreceptors provide the basis of almost all of our useful vision. Pathways originating from cones mediate high acuity, colour vision via so-called 'Midget' pathways, which dominate the central few millimeters of primate retina, including the fovea centralis ('fovea'). During early development foveal cones are amongst the first cells to differentiate, appearing as cuboidal, epithelial-like cells. Over the first few years of life they become slender, elongated cells with an elaborate axon, and highly elongated inner and outer segments. A slender shape facilitates close-packing of cones at the fovea, and is the anatomical stubstrate of high resolution vision. In the central fovea, the photoreceptor mosaic comprises cones exclusively, at their highest spatial density; these cones are narrower and more elongated than elsewhere in the retina.
Attainment of adult-like acuity functions in childhood is associated with a slender, elongated cone morphology at the fovea; loss of this morphology is a critical feature of both age-related macular degeneration (AMD) and retinal detachment. Despite the critical relationship between cone shape and visual function, the mechanisms that mediate morphological differentiation during development, and the maintenance of cones through adulthood and old-age, have not been identified. Work in this lab is directed at understanding the mechanisms underlying morphological differentiation of cone photoreceptors, development of the fovea and surrounding macula, and ageing and degeneration of the macula, as occurs in Age-related Macula Degneration.
Retinitis Pigmentosa
We are exploring the mechanisms which control the stability of nerve cells of the central nervous system, and whose breakdown results in neuronal death, causing the degenerative disease of the CNS. Many of our projects concern the retina of the eye, and especially the neurones specialised to detect light, the photoreceptors. These highly active and specialised neurones are amongst the most fragile of CNS cells; they degenerate in response to both genetic and environmental stresses. Retinitis pigmentosa (RP) is a diagnosis given to a group of diseases where the insidious death of retinal photoreceptor occurs causes blindness. RP affects 1 person in 4,000, thus about 5,000 Australians and 1-2 million people world-wide. Patients are usually in their late teens or early 20's when diagnosed and they face a life of gathering blindness with no effective treatment. Our laboratory is part of a world-wide effort to find effective treatment.
Effects of environmental factors on the rodent retina
Extensive work has been done on the causes of retinal degenerations. About 50% are clearly genetic, the other 50% occur without family history. Several features of retinitis pigmentosa also remain unexplained, particularly the relentless progression of the disease. Many forms of RP are caused by genetic mutation of rod-specific genes, yet the degeneration spreads from the rods to the cones, causing the loss of the entire photoreceptor population and blindness. Recent work in our laboratory led us to formulate an "oxygen toxicity" hypothesis, to explain the progressive nature of the disease. In this series of studies we are looking at the effects of different oxygen levels or light intensity levels on photoreceptor survival in normogenetic and degenerative retinae. By understanding the mechanisms underlying retinal degenerations, we will be able to model retinal degenerations and to study the effects of therapeutical interventions on these theoretical models, and to use our knowledge in clinical trials.
Protective mechanisms in the rodent retina
Examining the effects of changing environmental factors on the progress of retinal degneration, genetic or environmental, we are learning the process of the disease and the protective mechanisms by which the retina fights to survive. It has become clear in recent years that the degeneration takes place against a background of active resistance by the retina. The mechanisms by which the retina protects itself are also becoming clear. The retina is able to secrete proteins - sometimes called factors - which somehow protect retinal cells against damage. The mechanisms of secretion and action of these factors remain largely unknown. In this series of experiments we assess the role of protective (neurotrophic) factors in the normal retina's resistance to stress, such as light damage, identify the high-affinity receptors involved and trace their regulation by genetic and environmental stress. By using electroretinography we also assess the direct effects of these factors on photoreceptor function.
Roles of Mitochondria in Retinal Degenerations
Mitochondria serve (at least) 3 functions in every cell. They are the site of oxidative metabolism, and the source of signals which induce or suppress apoptotic (programmed) cell death. Mitochondria are abundant in photoreceptors, and we have begun testing whether mitochondrial damage is a factor in photoreceptor degeneration. We have shown for the first time that deletions in mtDNA (mitochondrial DNA) are abnormally frequent in degenerating retina. Recent studies have shown that somatically aquired mutations such as deletion of mtDNA are caused by oxygen damage or UV irradiation during the life of the individual. Accumulation of these somatic mutations in postmitotic cells (such as neurones) causes bioenergetic deficiency leading to age-associated dysfunction of cells and organs. An accelerated accumulation of mtDNA fragmentation leads to premature ageing and/or degenerative diseases. In this study we are screening photoreceptors of normal ageing and degenerative retinae . We are also looking at the role of mtDNA deletions in light induced retinal degenerations.
Retinal cell damage and repair: development of cellular biology based therapies
Photoreceptors are the light sensitive cells in the retina, and the sites where light is captured and transformed from electromagnetic waves to neural signals. Thus, photoreceptors are making the first steps in the process of vision. Damage to the photoreceptors leads to severe visual disturbances or blindness. Understanding the mechanisms that lead to photoreceptor damage and the processes by which the retinal tissue is trying to heal damaged cells are important. To find out more about the repair systems of the retina, we are using rodent models of retinal degenerations to follow the progression of cell damage and repair. Using genetic and environmentally-induced retinal dystrophy models, we are looking at signs of reversible and irreversible damage in photoreceptors, and the long-term consequences of cell loss on the function and structure of the retina. Changes in retinal metabolism, mitochondrial status and protective factor expressions are the focus of our investigations. Using our understanding of the cell biology of these cells and the protective mechanisms, we are developing non-invasive therapeutical approaches to prevent or slow photoreceptor degenerations.
Visual Ecology
We aim to understand the evolution and adaptive significance of eye specialisations in animals. One of our major projects at the moment is to establish an inventory of visual tasks in fiddler crabs. We also use a mobile robotic gantry to reconstruct the views seen by flying insects. For further details see Visual Ecology webpage.
Insect Vision, Perception and Navigation
Insects such as honeybees are impressive
navigators despite their relatively small brains and simple nervous
systems. We aim to elucidate principles of vision, flight control
and navigation in honeybees through behavioural experiments.
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Research School of Biological
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The Australian National University
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Student Opportunities
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Links
Centre
for Visual Sciences (CVS)
Australasian
Ophthalmic and Visual Sciences Meeting (AOVSM)
Visual Ecology
A stereotaxic atlas of the
wallaby brain
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