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 Collaborators
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 Alexander Burton, Research Fellow. Alex completed his Bachelor of Nursing in 1998 and Bachelor of Science(Hons) in 2004. Under Professor Macefield he completed his PhD in 2009 where he investigated the autonomic responses to painful stimuli in healthy human subjects and those with spinal cord injuries. Alex is also skilled in the areas of pain, sleep quality, anxiety and mood assessment and his research has been published in high quality peer-reviewed international journals. As a postdoctoral researcher, Dr Burton established a human autonomic laboratory investigating post-infective fatigue syndrome with A/Prof Ute Vollmer-Conna, which was successful in attracting significant funding. Alex is currently exploring the effects of tonic pain on muscle spindle activity. He is particularly interested in seeing how one's perception of muscle effort, control and proprioception is affected during pain. He is also interested in knowing why some people show increases in sympathetic activity during pain, while others do not.
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.
Dr Rania Fatouleh, Research Fellow. Rania received her PhD from Western Sydney University School of Medicine in 2015. Her thesis studied the functional and structural changes in the brain in patients with obstructive sleep apnoea (OSA) before and after treatment with continuous positive airway pressure (CPAP). This aimed to improve our understanding of the disturbances in autonomic control that manifest in OSA. Her current postdoctoral position with Professor Macefield aims to utilize her previously established techniques of recording concurrent microneurography and fMRI to understand the brain changes associated with high levels of muscle sympathetic nerve activity (MSNA) in patients with renovascular hypertension. This will extend our understanding of the cortical and subcortical areas of the brain responsible for generating sympathetic outflow in this condition in humans.
Dr Elie Hammam, Research Fellow. Elie received his PhD from Western Sydney University School of Medicine in 2015. 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).
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, Master of Philosophy (Medicine) 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.
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. an> David is the recipient of a current NHMRC project grant,Neural Mechanism of Bone Painand 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.
James Dunn, PhD student. A graduate of Western Sydney University's Bachelor and Honours programs in Advanced Science, James has continued his research at WSU into his postgraduate studies.The focal point of his PhD is the investigation of the role small unmyelinated fibres plays in both normal function and in neuropathic conditions such as allodynia and diabetic neuropathy.