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
Generation Of Complex Responses In Retinal Ganglion Cells
Funder
National Health and Medical Research Council
Funding Amount
$490,500.00
Summary
The retinal ganglion cells, whose axons form the optic nerve, comprise numerous distinct types, which respond to visual stimuli in either a simple or complex manner. The project will investigate how the complex responses of the direction-selective ganglion cells (DSGCs) and the local-edge-detector ganglion cells (LEDs) are generated. It appears that the retinal neurons providing inhibitory input to DSGCs and LEDs use different neurotransmitters, and the project will investigate how this shapes t ....The retinal ganglion cells, whose axons form the optic nerve, comprise numerous distinct types, which respond to visual stimuli in either a simple or complex manner. The project will investigate how the complex responses of the direction-selective ganglion cells (DSGCs) and the local-edge-detector ganglion cells (LEDs) are generated. It appears that the retinal neurons providing inhibitory input to DSGCs and LEDs use different neurotransmitters, and the project will investigate how this shapes the response properties of the ganglion cells. This will be done both by recording the visually evoked responses of the ganglion cells in an isolated preparation of the retina and by using two-photon laser-scanning microscopy to functionally image the neuronal interactions between the neurons that inhibit the DSGCs.Read moreRead less
The retina lines the back of the eye and sends multiple movies of the visual world to the brain. This project aims to investigate how these multiple information channels are created. Descriptions of the basic pattern of wiring in the healthy retina will help clinical researchers to understand the disruptions that occur in visual disease. The precision of normal retinal wiring also delineates the precision required to restore normal function to a diseased or degenerating eye.
Integration Of Information By Cells In Mammalian Visual Cortices: Role Of Feedforward And Feedback Inputs.
Funder
National Health and Medical Research Council
Funding Amount
$294,098.00
Summary
In highly 'visual' mammals, such as humans or domestic cats information channels originating in the retina extract and process in parallel information about certain features of the visual world such as shape or motion. The extracted information is sent to the primary visual cortex in the brain. The primary visual cortex 'distributes' this information to different 'higher-order' cortical areas which process the information further. Nerve cells in visual cortices have clearly defined receptive fie ....In highly 'visual' mammals, such as humans or domestic cats information channels originating in the retina extract and process in parallel information about certain features of the visual world such as shape or motion. The extracted information is sent to the primary visual cortex in the brain. The primary visual cortex 'distributes' this information to different 'higher-order' cortical areas which process the information further. Nerve cells in visual cortices have clearly defined receptive fields (RFs), that is, regions of the visual space from which appropriate visual stimuli will activate the cell. Contrary to the previous assumptions however, many of the basic RF properties of cortical neurones are not static but appear to depend on constant dynamic interplay between different components of nerve network in which the neurones are embedded. We wish to study the dynamic changes in the spatial structure of RFs of single neurones in mammalian primary visual cortex. We will examine changes in the structure of RFs of shape processing neurones when low contrast, large visual stimuli are presented. Since the low contrast stimuli extending beyond the confines of RFs of cortical neurones are akin to those in the natural visual scenes we hope to gain insights concerning mechanisms underlying perceptual processing of shapes in natural scenes. We will also study the spatial organization of RFs of neurones in primary visual cortex during reversible inactivation of higher-order visual areas. This will allow us to gain insights concerning the role of 'feedback' projections from the higher-order areas. Furthermore, we will study the responses of cells in one of the higher-order motion processing cortical areas. Comparing the responses in this area to complex motions during normal conditions with those during reversible inactivation of one of the reciprocally connected areas will provide us with insights concerning the mechanisms underlying processing of complex motions.Read moreRead less
The Role Of Vestibular Efferents In The Mammalian Vestibulo-ocular Reflex.
Funder
National Health and Medical Research Council
Funding Amount
$323,341.00
Summary
The aim of this study is to determine how a group of nerve fibres that travel from the brain to the balance organ alter balance function in mammals. Balance function in mice will be tested under conditions that modify the balance system response. Results will be compared between normal mice and mutant mice in which these nerves do not function. This work will determine how these nerves alter balance function and whether they are a viable target for future patient treatments.
The Role Of Adipokines In Modulation Of Gastric Vagal Afferent Satiety Signals
Funder
National Health and Medical Research Council
Funding Amount
$624,535.00
Summary
When we feel full after a meal it is the result of a variety of different nerve signals from the gut in response to distension of the stomach and specific nutrients. These signals are disordered in obesity and may be influenced by factors released from fat stores in the body. The aim of this project is to determine how these factors interact with gastric nerve satiety signals and thus identify targets for the pharmacological treatment of obesity.
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.
Dizziness, vertigo, and imbalance affect nearly half the population by the age of 60 and balance-related falls, especially in the elderly, are a serious health concern. Surveys of primary care doctors have shown that dizziness and vertigo are as prevalent as hypertension and angina, and approximately 40% of the population experience dizziness severe enough to seek medical attention. Unfortunately, most symptoms are not relieved by currently available medical treatment. There is, however, a remar ....Dizziness, vertigo, and imbalance affect nearly half the population by the age of 60 and balance-related falls, especially in the elderly, are a serious health concern. Surveys of primary care doctors have shown that dizziness and vertigo are as prevalent as hypertension and angina, and approximately 40% of the population experience dizziness severe enough to seek medical attention. Unfortunately, most symptoms are not relieved by currently available medical treatment. There is, however, a remarkable hidden reserve of 'self-repair' in the balance system that can be triggered under certain conditions. We call this process 'vestibular compensation' and if we can understand those conditions and discover the means by which this reserve affects the nervous system, we may be able harness its power to alleviate the all distressing symptoms of imbalance. Perhaps we may even be able to apply these principles to other critical systems that may need repair. We propose to look at a key region in the central nervous system that is responsible for processing balance signals and may be very important in 'vestibular compensation'. We will try to activate this recovery process under controlled conditions so that we can understand the changes that occur. Specifically we will examine the role of vestibular (balance) neurons in the central nervous system that appear to be modified following trauma of the inner ear balance organs. We will use our new recording techniques to examine these vestibular neurons to see how their intrinsic properties may change and what external or internal factors influences this change. Our aim is to understand what factors promote and what factors inhibit full recovery.Read moreRead less
The human brain has many subdivisions (�areas�) that are dedicated to vision, but in many cases their functions remain unclear. This project will study an area located deep in the brain, about which very little is known, and which appears to be affected from early stages in conditions such as Alzheimer�s disease. By understanding the patterns of electrical activity of cells in this region, and their connections with other brain areas, we hope to decipher their contribution to sensory cognition.