Neuronal Linking Of Attention, Perception And Action
Funder
National Health and Medical Research Council
Funding Amount
$586,469.00
Summary
We are able to perceive and interact with the environment around us primarily because a filter of attention selects just the objects or features of relevance in the world and helps to make appropriate motor responses. This project will study how attentional networks of the brain operate to link our perception and action. An understanding of this process is fundamental to revealing the underlying pathology in many neurological conditions where attention is impaired.
One of the main trends in the evolution of the primate brain was the huge expansion of the cortical areas devoted to visual processing. However, the exact role of individual areas remains highly controversial, making detailed physiological and anatomical studies in suitable primate models a key step to elucidating their function in the human brain. We will address one particular aspect of this problem, namely the organisation of the cortical areas that provide visual control for skilled movement ....One of the main trends in the evolution of the primate brain was the huge expansion of the cortical areas devoted to visual processing. However, the exact role of individual areas remains highly controversial, making detailed physiological and anatomical studies in suitable primate models a key step to elucidating their function in the human brain. We will address one particular aspect of this problem, namely the organisation of the cortical areas that provide visual control for skilled movements. It is proposed that there are two parallel brain circuits involved in the analysis of motion, one tracking the movement of objects, and the other analysing a person s self-motion. Consider, for example, the task of a tennis player who has to return a serve. In order to achieve this, the brain must precisely integrate information about the ball s motion, as well as information about the player s speed and direction. This requires precise control of eye movements (to keep the eyes on the ball), as well as the ability to control the limb and trunk muscles. The aim of this study will be to map the anatomical framework underlying our ability to process all the relevant visual motion information, and to coordinate the appropriate motor responses. Such work is fundamental for understanding the functional organisation of the brain. It also has the potential to lay the groundwork for developments in areas of applied research, including medicine (e.g. the design of better rehabilitation strategies for people with brain damage), robotics- artificial intelligence (e.g. the improvement of artificial systems capable of vision), and the cognitive sciences (e.g. a better understanding of factors that limit human responses to visual stimuli).Read moreRead less
Effects Of Prism Adaptation On Space Perception Following Chronic And Reversible Cortical Lesions
Funder
National Health and Medical Research Council
Funding Amount
$319,336.00
Summary
Damage to one side of the brain following a stroke often produces a debilitating disorder called spatial neglect. Affected patients persistently ignore objects, sounds or touches on the side of space opposite their brain injury. This disorder occurs despite normal sensory function, and reflects damage to the brain's internal representations of one side of space, causing patients to behave as if that side of space no longer exists. Spatial neglect is difficult to rehabilitate and is a major predi ....Damage to one side of the brain following a stroke often produces a debilitating disorder called spatial neglect. Affected patients persistently ignore objects, sounds or touches on the side of space opposite their brain injury. This disorder occurs despite normal sensory function, and reflects damage to the brain's internal representations of one side of space, causing patients to behave as if that side of space no longer exists. Spatial neglect is difficult to rehabilitate and is a major predictor of poor functional recovery after stroke, but there are no effective treatments for it. A promising new treatment for spatial neglect has been recently discovered, which involves patients practicing pointing to a visual target while wearing spectacle-mounted prism lenses that systematically correct for their altered view of the world. Following a brief period of this training, patients' show increased ability to perceive visual objects presented to the previously neglected side of space. Studies have shown that the prism treatment can have long-term benefits for many neglect sufferers. However, it is not known what the brain mechanisms underlying the treatment effects are, and to what degree the effects generalize to all affected senses. The proposed project aims to investigate whether prism treatment ameliorates spatial neglect of sounds as well as visual objects in a group of stroke patients. The project will also systematically examine which part of the brain is critical for the beneficial effects of prism treatment by using focal magnetic stimulation to create reversible, virtual lesions in the brains of healthy participants. Addressing these issues has clear implications for identifying suitable candidates for the treatment, and for understanding how the sensory world is represented in the human brain.Read moreRead less
Auditory Attentional Processes In Stroke Patients With Unilateral Neglect And In Normal Listeners
Funder
National Health and Medical Research Council
Funding Amount
$281,900.00
Summary
A common consequence of a stroke affecting the parietal lobe of the right hemisphere of the brain is a failure to attend to stimuli presented to the left side of the patient. This disorder, called unilateral spatial neglect, affects up to 50% of all stroke sufferers, and poses a significant problem for recovery of function. Neglect has been most widely studied in the modality of vision. Although neglect of auditory stimuli and of stimuli in other modalities has been reported, it has been studied ....A common consequence of a stroke affecting the parietal lobe of the right hemisphere of the brain is a failure to attend to stimuli presented to the left side of the patient. This disorder, called unilateral spatial neglect, affects up to 50% of all stroke sufferers, and poses a significant problem for recovery of function. Neglect has been most widely studied in the modality of vision. Although neglect of auditory stimuli and of stimuli in other modalities has been reported, it has been studied in much less detail, and the relationship between visual and auditory neglect has not been investigated using tasks of similar complexity. One aim of this project is to examine the relationship between auditory and visual neglect using tasks that are carefully matched for complexity and cognitive demands. A second aim relates to the important recent discovery that substantial changes in a visual scene can go unnoticed unless the observer's attention is drawn to them, a phenomenon termed change blindness. The project will examine the ability of normal listeners and of stroke patients to detect changes in complex auditory environments in which sounds arise from multiple sources located in different regions of space. We aim to establish whether there is a change deafness phenomenon analogous to change blindness, and if this is exacerbated in stroke patients with neglect. The results of this project will increase our understanding of the nature of normal auditory attentional processes and of their disruption as a consequence of stroke. The importance of these studies derives from the fact that hearing and attention to auditory stimuli serve a critical role in human communication and as an early warning system for events in the environment that are not within a person's visual field. Increased understanding of disturbances in auditory attention in neglect patients could lead to better rehabilitation of neglect, for which there is currently no effective treatment.Read moreRead less
Representation Of Spatial Coordinate Systems Within Posterior Parietal Cortex And Hippocampus
Funder
National Health and Medical Research Council
Funding Amount
$43,759.00
Summary
To accurately reach for an object or walk from one room to another, our brains need to be able to locate objects around us and detect obstacles in our path. Our amazing ability to make an accurate eye movement directly towards an object such as a cup of tea and move our hand smoothly and directly to the cup is something we all take for granted. However, this ability requires enormous computational complexity which our brains have evolved to handle with ease. We plan to determine the parts of the ....To accurately reach for an object or walk from one room to another, our brains need to be able to locate objects around us and detect obstacles in our path. Our amazing ability to make an accurate eye movement directly towards an object such as a cup of tea and move our hand smoothly and directly to the cup is something we all take for granted. However, this ability requires enormous computational complexity which our brains have evolved to handle with ease. We plan to determine the parts of the brain that perform these computations by using a relatively new technique called functional magnetic resonance imaging or fMRI. This is a non-invasive technique that requires a person to lie in an MRI scanner and perform simple eye movement tasks while the scanner takes images of the brain. With this technology we are able to determine which regions of the brain are most active during the performance of each task, thereby giving us an insight into how the brain works. An area of the brain called the parietal lobe is thought to be involved in the localization of objects, such as reaching for a cup of tea. We will study this area using fMRI to determine how a map of space is represented within the parietal lobe. This region of the brain communicates with another region, the hippocampus which is thought to be involved in navigation, such as walking about the house or driving in the city. Functional MRI will be used to study the hippocampus of our subjects while they perform simple navigational tasks through a maze which is simulated on a computer screen. This will reveal the role hippocampus plays in navigation and the relationship between the parietal lobe and hippocampus. We hope that the greater understanding of hippocampus that will arise from this study will enable us to devise a robust method for imaging hippocampal function with fMRI. We expect that these techniques will aid in the diagnosis of hippocampal abnormalities in patients with temporal lobe epilepsy.Read moreRead less
A decade ago the adult brain was thought of as a structurally-fixed organ. Against this are well-documented cases of slow recovery after massive injuries or stroke. Simple models of brain injury using the tactile, visual and auditory systems of animals as models have now revealed multiple stages of recovery (plasticity). Some of these are inbuilt into the wiring of the neural systems such that functional plasticity can result without the need for any structural or cellular changes. A second grou ....A decade ago the adult brain was thought of as a structurally-fixed organ. Against this are well-documented cases of slow recovery after massive injuries or stroke. Simple models of brain injury using the tactile, visual and auditory systems of animals as models have now revealed multiple stages of recovery (plasticity). Some of these are inbuilt into the wiring of the neural systems such that functional plasticity can result without the need for any structural or cellular changes. A second group of plastic phenomena depend upon minute changes in the connections between neurons and these are invoked in the first few days following an injury (synaptic plasticity; changes in the pattern and strength of the connections between neurons). Aside from being model systems, there are also parallels of this plasticity with clinical situations such as losses in hearing and sight, and of the adaptations made by the brain in response to prosthetics (e.g. bionic ear) and resorative surgery but the degree of relevance for these situations is unclear. An intriguing aspect of the experiments on auditory and visual systems is that neurons with inputs from both ears, or both eyes, undergo the plastic changes when the relevant sense organ on only one side is damaged but the other is intact. In fact, on the basis of the limited available evidence, it appears that the changes are independent of there being a normal input from the other side. This is difficult to explain in terms of the modern understanding neuronal plasticity at a cellular level. It is thus proposed to study both auditory and visual models of this brain plasticity with stimuli which are systematically varied to extract the extent of bilateral interaction in the induced plasticity. This will enable prediction of how these plasticity mechanisms will be involved in adaptations made to prosthetics and surgical corrections.Read moreRead less