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Professor Vaughan Macefield
Senior Lecturer: Dr David Mahns
Professor Vaughan Macefield
Prof Vaughan Macefield is Foundation Chair of Integrative Physiology at the School of Medicine, Western Sydney University, and a Conjoint Senior Principal Research Fellow at Neuroscience Research Australia (NeuRA). He is also the Deputy Dean and Director of Research at the School of Medicine.
A former NHMRC Senior Research Fellow, he completed his PhD in neurophysiology at UNSW in 1986, and undertook advanced training in human neurophysiology in Sweden and the US, before establishing his own laboratories at Prince of Wales Medical Research Institute (now NeuRA) in 1994.
Vaughan is the National and NSW State Coordinator of the Australian Brain Bee Challenge, Australia's only neuroscience competition for high school students. He also actively promotes science to school audiences through school site visits and in-house presentations, as well as contributing to events such as Science in the Suburbs and the Sydney Science Festival.
Professor Macefield's Research
Professor Macefield specializes in recording from single nerve fibres via tungsten microelectrodes inserted into the peripheral nerves of awake human subjects, and is known nationally and internationally as a world expert in recording the firing properties of human sympathetic neurones (e.g. those supplying blood vessels) in health and disease and as a leading investigator in human sensorimotor control. In 1996 he was awarded the $10,000 Sunderland Award for "Excellence in Sensorimotor Biology."
He has active collaborations with many groups in universities and hospitals in Australia and in Sweden and the USA, and has attracted postdoctoral scientists from Sweden, Denmark, Canada and Australia. For over 10 years Prof Macefield has been been examining the changes in control of the autonomic nervous system following human spinal cord injury. Over the last decade his research has extended into the study of pain and its effects on the autonomic and somatic nervous systems, using brain imaging techniques (fMRI) to study the processing of pain originating in muscle and skin. Most recently, he has developed the technique of concurrent microneurography and fMRI, through which sites responsible for the generation of sympathetic nerve activity to muscle or skin can be identified in the human brain.
His research is currently supported by the National Health and Medical Research Council of Australia and the Australian Research Council.
Professor Macefield's Team
- Dr Rachael Brown, Associate Research Fellow. Rachael was formerly a clinical nurse specialist working in the acute spinal unit, and it was her interest in blood pressure control following a spinal cord injury that lead her to undertake a PhD with Professor Macefield which she received in 2009. She has since been working with Professor Macefield, utilizing the technique of microneurography, with a focus on cardiovascular control. Recently, Rachael published work showing, for the first time, that watching a 'first person' video of someone else running can increase cardiovascular parameters such as heart rate, despite the fact the subject is sitting relaxed with no muscle activity. Her current research involves examining gender differences in muscle sympathetic nerve activity during long-lasting muscle pain.
- Dr Chloe Taylor, Senior Lecturer. Chloe undertook her PhD at Liverpool John Moores University in the UK and has been employed as a lecturer in Sport and Exercise Science at Western Sydney University since July 2011. Chloe's research focus is cardiovascular control, in particular the responses to physiological challenges such as exercise and orthostasis, and the effects of time and day. A key area of her research involves the assessment of cardiovagal and sympathetic baroreflex sensitivity and its role in blood pressure regulation with respect to these challenges. Chloe is currently conducting a study of inter-individual differences in blood pressure responses to mental and physical stressors, looking specifically at the effects of sex and ageing. She is also involved in a project using microneurography to measure sympathetic nerve activity to contracting muscles, exploring the roles of central command and the metaboreflex.
- Rania Fatouleh, PhD student. Rania's work aims to identify the brain sites responsible for the increase in muscle sympathetic nerve activity (MSNA) in obstructive sleep apnoea (OSA). Increased MSNA is a precursor to hypertension and elevated cardiovascular morbidity and mortality. However, the mechanisms underlying the high MSNA in OSA are not well understood. By recording MSNA concurrently with functional Magnetic Resonance Imaging (fMRI) Rania is aiming to identify the central processes responsible for the sympathoexcitation. Long-term treatment with continuous positive airway pressure (CPAP) decreases MSNA in OSA but this is not reflected in a fall in blood pressure. Therefore Rania is testing the same OSA patients after 6 and 12 of CPAP to detect all changes after treatment.
- Elie Hammam, Associate Research Fellow. Elie received his PhD from Western Sydney University School of Medicine. He undertook a series of neurophysiological studies locally and at the Hong Kong University of Science and Technology (HKUST) to better understand the vestibular system's contribution to the control of blood flow and blood pressure in human subjects. Using microneurographic recordings of sympathetic nerve activity, he showed that low-frequency postural changes induce a robust modulation of sympathetic outflow to both muscle and skin, even at levels of motion below perceptual threshold. In addition, Elie has an interest in employing microneurography and functional magnetic resonance imaging (fMRI) of the brainstem and the whole brain in heart failure patients. He was awarded a scholarship to the School of Advanced Neuroscience Imaging from the International Brain Research Organisation (2013) and highly commended for the Vice Chancellor's Excellence Award in Engagement (2014).
- Khadigeh El Sayed, PhD student. Under Professor Vaughan Macefield's supervision, Khadigeh completed her Honours degree in 2011. Her project aimed at assessing the role of the vestibular system in cardiovascular control which, in turn, looked at how vestibular inputs from each side of the head modulate sympathetic nerve activity to muscle and skin. This was achieved by making bilateral recordings with the application of low-frequency (0.08Hz) sinusoidal Galvanic Vestibular Stimulation (sGVS) using microneurography. Currently, her PhD project involves the investigation of inter-individual differences in muscle sympathetic nerve activity (via microneurography) and blood pressure responses to mental and physical stressors in healthy young males and females. Following this, she will also look at the effects of aging on these responses.
- Daniel Boulton, PhD student. Daniel is a Sport and Exercise Science graduate who completed Honours in 2012 and is currently undertaking a PhD degree. Daniel's research is investigating the role of central command and peripheral reflexes in the control of muscle sympathetic nerve activity to active and inactive limbs during exercise. Microneurography is used to directly record nerve activity in both resting and exercising limbs.
- Michael Leitch, PhD student. Michael has previously shown that irregular trains of stimuli, emulating the firing of actual motoneurones during voluntary contractions, produce greater contractile responses of single motor units than regular (non-physiological) trains of identical mean frequency but zero variability. In the current research he intends to extend this line of reasoning, through a series of experiments, utilizing intraneural microstimulation of single human motor axons. Michael will attempt to create optimal patterns that maximize the contractile responses of human motor units. By using optimized patterns of stimuli that emulate the firing of real motoneurones during voluntary contractions he hopes to be able to contribute important new information on muscle physiology and develop novel means of applying functional electrical stimulation (FES) to muscles that have been weakened or paralysed by stroke or spinal cord injury.
- James Wright, PhD student. James is attempting to build a closed loop neuroprosthetic assistive device for suffers of motor impairment. By using microneurography to record afferent sensory activity during object manipulation the project aims to incorporate natural sensory feedback as a sensor signal in the control of a neuroprosthetic.
- Sophie Kobuch, PhD student. Sophie is studying the effects of long-lasting experimental muscle pain, induced by hypertonic saline solution, on sympathetic outflow to muscle in awake human subjects. It has been shown that in some subjects, this form of pain causes muscle sympathetic nerve activity, blood pressure and heart rate to fall, while in others they increase. This is despite the fact that both groups of subjects rate the pain identically, and describe it identically. Sophie will investigate whether baseline physiological and psychological parameters could predict the direction of the sympathetic response. Furthermore, she will be using concurrent microneurography and functional brain imaging to identify areas in the brain responsible for the sustained increase or decrease in muscle sympathetic nerve activity in response to long-lasting experimental muscle pain in humans.
- Thomas Knellwolf, Bachelor of Medical Research student. Thomas's research is centred on the relationship between the vestibular system and muscle spindles. He has previously demonstrated there is no vestibular modulation of spindle afferents in subjects whilst in a near-vertical position. His current research involves the further examination of this relationship in freestanding subjects with postural perturbations. This will be achieved by recording from single unit afferents innervating muscle spindles located in the muscles of the foot, by way of the microneurographic technique, whilst applying sinusoidal Galvanic Vestibular Stimulation (sGVS) at a range of frequencies. Subjects will be either seated or freestanding on a motorized platform that will undergo low-frequency sinusoidal movements. By comparing the degree of modulation between seated and freestanding subjects, with and without postural perturbations, he hopes to characterize the conditions under which muscle spindles experience independent vestibular modulation.
- Natasha Singh, Master of Research student. Natasha's research aims to characterize the physiological changes occurring during slow actual or virtual motion at low frequencies. The investigation will identify at which frequencies of movement relaxation and sleepiness - symptoms of sopite syndrome - are induced. Her study will employ sinusoidal galvanic vestibular stimulation (sGVS), a means of selectively stimulating the vestibular apparatus, as well as slow sinusoidal movements of seated subjects, Natasha's study will use stimulation methods at very low frequencies, below 0.08 Hz, to determine how well these frequencies entrain muscle and skin sympathetic nerve activity - recorded using microneurography - and induce the symptoms of sopite syndrome.
Dr David Mahns is a Senior Lecturer in Integrative Physiology at the School of Medicine, Western Sydney University. David completed his PhD in cardiovascular physiology at Prince of Wales Medical Research Institute in 1999, before undertaking postdoctoral training in neurophysiology at the University of New South Wales and being appointed as a Lecture in Physiology at the University of New South Wales in 2003. In 2006 David established his own laboratories at the Western Sydney University.
Dr Mahns' Research
In most circumstances we can readily distinguish between painful and non-painful stimuli. It is widely appreciated that non-painful and painful sensations rely on the activation of distinct groups (or classes) of sensory nerves. Despite this common perception, it remains unclear whether distinguishing between innocuous (non-painful) and noxious (painful) stimuli result from the activation of single class of sensory nerves, convergence of inputs arising from multiple classes or the pattern of activation within the central nervous system. The broad aim of Dr Mahn's work is to define the contribution of different nerves (and central pathways) to pain arising from deep (e.g. viscera, muscle and bone) and superficial (skin) structures. In order achieve this his team is using a range of recoding techniques, that allow recording from individual nerve fibres, and psychophysical techniques that allow the group to better understand how the nervous system detects and relays information about pain.
David is the recipient of a current NHMRC project grant, Neural Mechanism of Bone Pain and a Western Sydney University Research Grant, Peripheral encoding of forces associated with manipulation by tactile afferents. He is involved in several research projects involving collaborations with Prof Macefield and Prof John Morley (Western Sydney University), Dr Ingvars Birznieks (Neuroscience Research Australia), Dr Richard Vickery (University of New South Wales) and A/Prof Gustavo Duque and Dr Wei Li (University of Sydney).
Dr Mahns' Team
- Dr Saad Nagi, Research Fellow. What triggers the crossover between non-painful and painful sensations is yet to be fully elucidated especially in clinical pain-states such as allodynia, i.e. pain evoked by otherwise innocuous (tactile/cold) stimuli. Saad's research interests revolve around the mechanisms underlying the most intrinsic imprints of sentience such as touch, temperature and pain. Psychophysical tools are being employed in healthy and clinical individuals to explore the interplay of these sensations, and the role of different peripheral nerve fibres in coding of stimulus features. Recent investigations have demonstrated that a class of low-threshold unmyelinated mechanoreceptors, dubbed C-tactile fibres, mediates the crossover between pleasurable-touch and painful-touch, thereby unveiling a novel substrate of tactile allodynia, or more broadly pain modulation. Further investigations are under way with the aim of determining the response properties and innervation patterns of this afferent class, in addition to exploring the role of cognitive influences in pain modulation.
- Sumaiya Shaikh, PhD student. Sumaiya's previous work was to determine the neural correlates of affective sensations with pain using psychophysical methods. She is also a part of the broader project testing pain symptoms behaviourally duing sutureless peripheral nerve repair and is currently involved in projects which test the anatomical changes in cutaneous sensory mediators after injuries. She is also using a range of immunohistochemical techniques and staining methods to visualise what derives the change, centrally and/or peripherally after acute and chronic nerve injuries particularly focusing on tactile and cold allodynia.
- Mohamad Samour, PhD student. The sensory function of the peripheral and central nervous system is frequently described as following predictable or rigid rules wherein individual nerves perform specific tasks with little overlap. However, it is increasingly appreciated that sensory systems can operate in a diversity of modes in effect revealing an underlying plasticity within the sensory systems. Through human psychophysical studies and electrophysiological experiments, my goal is to understand the fundamental functions of one of the most underrepresented group of fibres, C fibres, in reference to pain, tactile sensation and thermal sensibility.
- James Dunn, Honours student. James is a graduate of the Bachelor of Science (Advanced) program at Western Sydney University, majoring in human biosciences. The objective of his current research is to re-explore Weber's illusion, a somewhat forgotten tactile illusion that makes the body perceive cold objects as heavier than normal ones despite there being no difference in the weight of the objects. Along with the rest of the research group James will also investigate possible ways in which transcranial magnetic stimulation can impact upon pain memory and pain perception.