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 Saccadic Eye Movements On Perception And Visual Memory.
Funder
National Health and Medical Research Council
Funding Amount
$255,750.00
Summary
We all make rapid eye movements, called saccades, three times a second all our waking lives. They allow us to direct our gaze at what catches our attention, but they sweep images across our retinas and alter all the linkages between the eyes and the brain. The question at the heart of this project is how the visual system maintains perceptual stability given the disruption to the flow of visual input that saccades necessarily cause. It has to do more than suppress disturbing signals; it has to l ....We all make rapid eye movements, called saccades, three times a second all our waking lives. They allow us to direct our gaze at what catches our attention, but they sweep images across our retinas and alter all the linkages between the eyes and the brain. The question at the heart of this project is how the visual system maintains perceptual stability given the disruption to the flow of visual input that saccades necessarily cause. It has to do more than suppress disturbing signals; it has to link the present with the past. In recent years we and others have made substantial progress toward answering this question. In this project we plan a four-pronged attack that will take us further. We anticipate that our results will reveal how the visual system maintains and adjusts its representations of space and time, integrates signals from before and after saccades, and regulates the flow of information from memory to achieve a seamless melding of the present with the past. This project is not directed at any particular clinical problem, but disturbances of perception and memory are aspects of many clinical conditions. If we succeed in our aims what we discover will constitute a major scientific discovery which should find application to many conditions in which perception and memory are disturbed, from dyslexia to brain damage and even affective disorders such as schizophrenia and depression.Read moreRead less
Signalling Of Muscle Force By Golgi Tendon Organs During Exercise And Fatigue
Funder
National Health and Medical Research Council
Funding Amount
$181,320.00
Summary
It is a common experience for objects being carried to feel heavier and tasks needing muscular effort to become more difficult as one becomes tired and the muscles fatigue during exertion. The sensation of muscle force depends on two factors. One, a sense of the effort required to perform a task, is generated in the central nervous system and. The other, a sense of the force actually developed by the muscles, is generated in the muscles themselves by signals from sensory receptors called Golgi t ....It is a common experience for objects being carried to feel heavier and tasks needing muscular effort to become more difficult as one becomes tired and the muscles fatigue during exertion. The sensation of muscle force depends on two factors. One, a sense of the effort required to perform a task, is generated in the central nervous system and. The other, a sense of the force actually developed by the muscles, is generated in the muscles themselves by signals from sensory receptors called Golgi tendon organs. The sensation of muscle force and the heaviness of objects results from a combination of both senses, but the contribution of each is unknown. The aim of the project is to determine whether the disturbance of force sense in fatigued muscles results from changes in the way tendon organs signal the actual force developed by the muscles. This will be important for understanding how force sense is disturbed following exercise and in disease states, and for understanding the normal way muscle force is sensed in everyday situations. Disturbances of force sense after exercise will be documented in human subjects by asking them to generate what they perceive to be equal forces in both arms or legs, before and after one limb only is exercised. Errors in force estimation will show up as mismatches between the two limbs. The difficulty with human experiments is that the signals generated by tendon organs cannot be measured directly, but only inferred, perhaps wrongly. This difficulty will be overcome by measuring tendon organ activity directly in anaesthetised animals, where the muscles will be electrically stimulated to perform exercise similar to that in the human experiments. A change in tendon organ signalling will be taken to mean that similar changes in humans could be responsible for disturbances of force sense. In further experiments, the mechanism of the changes will be explored.Read moreRead less
Mechanisms Of Mechanotransduction In Primary Visceral Afferents
Funder
National Health and Medical Research Council
Funding Amount
$253,500.00
Summary
Mechanotransduction is the process whereby mechanical stimuli are converted into signals in sensory nerves. This forms the basis of touch, hearing, position sense and many aspects of internal perception. It also constitutes a major component of pain. Our group aims to discover the molecular basis of mechanotransduction in mammals, and in particular how it relates to signaling of events in the digestive system. We and our collaborators have been among the first to explore this question, and have ....Mechanotransduction is the process whereby mechanical stimuli are converted into signals in sensory nerves. This forms the basis of touch, hearing, position sense and many aspects of internal perception. It also constitutes a major component of pain. Our group aims to discover the molecular basis of mechanotransduction in mammals, and in particular how it relates to signaling of events in the digestive system. We and our collaborators have been among the first to explore this question, and have found that three genes are responsible for many aspects of mechanotransduction. Each gene is transcribed to produce a channel or pore in the membrane of sensory nerve fibres which responds to mechanical forces by allowing ions to enter and induce electrical signals. Our early findings in mice with disruption of individual genes indicate that a complex positive and negative interaction of these channels must underlie normal mechanotransduction. However, these channels must represent only a part of the transduction mechanism, with extracellular and intracellular anchors inevitably playing a major role. The identity of such anchoring proteins in mammals is currently emerging, and we are fortunate to have access to mice deficient in specific genes that will provide information about candidates for this role. Through our studies on mechanotransduction in the digestive system in parallel with our collaborators' studies on mechanotransduction in skin we shall not only identify the fundamental mechanisms of mammalian mechanotransduction, but also reveal which components of mechanotransducers are peculiar to the gut. Such peculiarities provide molecular targets for therapy of diseases in which alteration of mechanosensory signaling is itself an aim.Read moreRead less
Reflex Control Of Human Jaw Muscles By Periodontal Mechanoreceptors
Funder
National Health and Medical Research Council
Funding Amount
$405,173.00
Summary
An understanding of the functional connection between the jaw muscles and various receptor organs in and around the mouth is necessary to elucidate the process of chewing and its underlying rules. Unless the details of this functional connection in health and disease are thoroughly understood, the diagnosis and treatment of chewing related disorders will remain at the present state. For example: a We still do not know why chewing in edentulous subjects is less efficient and why the bite forces i ....An understanding of the functional connection between the jaw muscles and various receptor organs in and around the mouth is necessary to elucidate the process of chewing and its underlying rules. Unless the details of this functional connection in health and disease are thoroughly understood, the diagnosis and treatment of chewing related disorders will remain at the present state. For example: a We still do not know why chewing in edentulous subjects is less efficient and why the bite forces in these individuals immediately fall to about 20 % of the teethed value. Do jaw muscles in these subjects get weak because they get less support from the receptor organs around the teeth? a We still do not understand the cause-causes of the temporomandibular dysfunction (a painful disease involving jaw muscles) which forms 18.7 % of total dental patients consulted per week in South Australia. This South Australian study indicated that the current treatments (such as pain killers, night plates, massage) Ocures? only about the half of all patients. We cannot increase the success of the treatment if we do not fully understand the control mechanisms of chewing? It is expected that the results of this study will establish the functional connection between one of the most important receptor organs in the mouth (periodontal mechanoreceptors) to the jaw muscle motoneurons in subjects with healthy teeth and gums and will illustrate the importance of keeping the periodontium healthy for developing strong and smooth masticatory forces. This knowledge can also allow us to treat jaw related disorders by approaches that bring back normal operation of the system. For example, this knowledge may help us design active dentures that replace the missing support.Read moreRead less