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.
Visual Neuroethology - 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.
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.
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.
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.
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.
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.
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.
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.
