Chairs
Professor David Attwell FRS, University College London, UK
Professor David Attwell FRS, University College London, UK
David Attwell studied physics as an undergraduate in Oxford, and then did a PhD working on nerve and muscle with Julian Jack. After a post-doc in Berkeley working on the retina with Frank Werblin, he came to UCL as a Lecturer and is now Jodrell Professor of Physiology. His research has covered synaptic transmission and information processing in the CNS, the properties of glial cells, glutamate uptake and how it reverses and releases glutamate in ischaemia, the energy supply to the brain and its regulation at the capillary level by pericytes, and the cellular basis of BOLD imaging. He is a Fellow of the Royal Society and of the Academy of Medical Sciences.
09:10-09:40
Uses, misuses, new uses and fundamental limitations of MRI in cognitive science
Professor Robert Turner, Max Planck Institute for Human Cognitive and Brain Sciences, Germany
Abstract
When BOLD contrast was discovered in the early 1990s, it provoked an explosion of interest in exploring human cognition using brain mapping techniques based on MRI. Standards for data acquisition and analysis were rapidly put in place, in order to assist comparison of results across laboratories. Recently, MRI data acquisition capabilities have improved dramatically, inviting a rethink of strategies for relating functional brain activity at the systems level with its neuronal substrates and functional connections. This presentation will review the following questions:
a) What can structural and functional BOLD MRI reveal about human cognition that other techniques cannot provide?
b) In which areas of cognitive science has fMRI made major contributions?
c) What are the implicit assumptions underlying now-popular analysis techniques, and what are the flaws in these assumptions?
d) Can MRI-based myeloarchitectural parcellation of the cortex and high resolution fMRI methodology make these assumptions unnecessary?
e) Are there other ways of analyzing MRI/fMRI data that provide deeper insight?
f) Will cortical layer-specific fMRI enable questions of causality to be addressed, and what are the best candidate techniques for such acquisitions?
g) What are the likely fundamental limitations of all MRI and fMRI methods?
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Professor Robert Turner, Max Planck Institute for Human Cognitive and Brain Sciences, Germany
Professor Robert Turner, Max Planck Institute for Human Cognitive and Brain Sciences, Germany
Robert Turner played a key role in the invention of actively shielded gradient coils used widely in MRI, in the development of diffusion weighted imaging of the human brain, which allows assessment of brain connectivity and evaluation of stroke damage, and in the discovery of functional MRI by measurement of the effects of blood oxygenation changes. As a Max-Planck Institute Director in Leipzig, Germany, he has been engaged in the discovery of native cortical anatomical maps of individual living human brains using ultra-high field MRI.
He started his academic career as a physicist, studying maths and physics at Cornell University until 1968, and completed his doctorate in physics at Simon Fraser University, Vancouver. After three years as a post-doctoral physicist at the Cavendish Laboratory, Cambridge, he broadened his horizons by studying social anthropology at University College London. During the period of ethnographic fieldwork that followed, he encountered MRI, which had been recently invented, and realized that this technique could provide insight into basic aspects of human nature, via maps of human brain organization. Returning to physics as a lecturer at Nottingham University in 1984, he built his own MRI scanner in 1984, designed and built gradient coils for MRI, and assisted the Nobel Prize winning Sir Peter Mansfield in developing ultra-fast MRI techniques. As a Visiting Scientist at NIH between 1988 and 1994, he pioneered functional magnetic resonance imaging (fMRI) and diffusion weighted imaging. This led to his appointment as Wellcome Principal Research Fellow and Professor in Imaging Physics at the Institute of Neurology in London, where he established fMRI as a tool for cognitive neuroscience.
09:50-10:20
Neurovascular coupling: when its reliability as a marker of neuronal activity gets challenged
Professor Edith Hamel, Montreal Neurological Institute, McGill University, Canada
Abstract
Changes in neuronal activity are spatially and temporally coupled to concurrent changes in cerebral blood flow (CBF), a process known as neurovascular coupling (NVC) that forms the basis of several brain imaging techniques. Yet, it is unclear how reliable this coupling remains during altered brain states and, particularly, under pathological conditions. Using the whisker-to-barrel pathway, a well-established model of NVC, we tested whether the coupling between neuronal activity and CBF would be affected by changes in brain states induced by varying the levels of acetylcholine (ACh), a potent modulator of sensory processing. Under acute increases in ACh tone, whisker-evoked hemodynamic responses and neuronal signals (LFPs and band-limited power) were potentiated despite no change in the extent and identity of the neuronal network recruited within the activated barrel. Inversely, chronic ACh deprivation compacted the activated barrel and reduced both sensory-evoked hemodynamic and neuronal responses. Our findings indicate that hemodynamic signals dependably reflect changes in the activity of the neural circuit underlying sensory processing under states of enhanced ACh neurotransmission and in conditions of a cholinergic deprived network as seen in Alzheimer’s disease.
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Professor Edith Hamel, Montreal Neurological Institute, McGill University, Canada
Professor Edith Hamel, Montreal Neurological Institute, McGill University, Canada
Dr Edith Hamel is director of the Laboratory of Cerebrovascular Research at the Montreal Neurological Institute, McGill University, Montréal, Canada. Her research focuses on neuro-glio-vascular interactions that assure a proper blood supply to activated brain areas, a phenomenon known as ‘neurovascular coupling’. These interactions are at the basis of several brain imaging techniques that use hemodynamic signals to map changes in brain activity under physiological and pathological conditions. An important aspect of her research is dedicated to the understanding of how specific neuronal populations sculpt changes in neuronal activity in response to specific stimuli and how these changes are communicated to blood vessels. Another aspect of Dr Hamel’s research aims at understanding the impact of cerebrovascular alterations on cognitive failure in Alzheimer’s disease and vascular dementia. Dr Hamel has published over 135 peer-reviewed journal articles, and she is currently President of the International Society of Cerebral Blood Flow and Metabolism.
11:00-11:30
Vasomotion: a link from ultra-slow neuronal activity to blood oxygenation
Professor David Kleinfeld, University of California, San Diego, USA
Abstract
The blood-oxygenation-level-dependent (BOLD) fMRI signal is a central technology of modern cognitive neuroscience. An intriguing issue is that ultra-slow variations (~ 0.1 Hz) in the oxygenation of brain tissue appear to be mirrored across conjugate brain areas in the two hemispheres. This is referred to as ‘resting-state’ BOLD fMRI and this finding has been inverted in many studies of human cognition, so that ultra-slow co-fluctuations are interpreted as ‘function connections’. Yet the mechanism to support this interpretation remains to be discovered. Here we address this relation in awake mice through measurements of neuronal activity, tissue oxygenation, and conventional and ultra-large field two-photon imaging of vascular dynamics. We provide evidence that arteriole vasomotion can link ongoing, coordinated neuronal activity with ultra-slow oscillations in blood oxygenation. This result may justify inferring neuronal connections from synchronous ultra-slow vasodynamics between different brain areas.
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Professor David Kleinfeld, University of California, San Diego, USA
Professor David Kleinfeld, University of California, San Diego, USA
David Kleinfeld is a Distinguished Professor of Physics and of Neurobiology (courtesy) and currently holds the Endowed Chair in Experimental Biophysics. He trained in experimental physics with George Feher, then shifted his research efforts to the study of networks within nervous systems while a Member of Technical Staff at AT&T Bell Laboratories. His ongoing programs address the basis of exploration and active sensation within brainstem circuits and the relation of vascular architecture and vasodynamics to the control of blood flow within cortex. These two programs are synergistic and further involve the development of tools for neurological data acquisition and analysis. David is committed to the education of young neuroscientists. Beyond training protégés that have gone on to faculty positions at research universities, he has co-directed and/or lectured at postgraduate summer schools at Cold Spring Harbor Laboratory, Laval University, and the Marine Biological Laboratory for over two decades.
11:40-12:10
Model-based approaches that connect BOLD imaging and dopaminergic transmission in humans
Professor Read Montague, Virginia Tech Carilion Research Institute, USA and University College London, UK
Abstract
Using a simple sequential decision task we provide new data showing a cross cohort relationship between BOLD responses during the decision task and sub-second electrochemical estimates of dopamine and serotonin from the dorsal striatum. Not surprisingly the relationship among these three separate measures is not simple even allowing for the possibility that some features of the signaling are unique to the state of the subjects’ brains (i.e. Parkinson’s Disease or Essential Tremors). Dopamine and serotonin appear to correlate with error signals for experienced rewards and one form of counterfactual signals (what might have been gained or loss had the choice been different). Moreover, fluctuations in these two transmitters prospectively encode a subject’s strategy on their next choice (stay or shift) with dopamine carrying this information following a positive prediction error and serotonin carrying it following a negative prediction error. We speculate about the connection between the measured BOLD response and the measured neuromodulator response; however the results do suggest more complexity than is latent is models built solely around the BOLD response.
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Professor Read Montague, Virginia Tech Carilion Research Institute, USA and University College London, UK
Professor Read Montague, Virginia Tech Carilion Research Institute, USA and University College London, UK
Read Montague holds a Principal Research Fellowship from the Wellcome Trust and is a principal at the Wellcome Trust Centre for Neuroimaging. He is a professor of physics at Virginia Tech Carilion Research Institute where he is also founding director of the Computational Psychiatry Unit and Human Neuroimaging Lab. Montague's work lies at the intersection of computational neuroscience and neuroimaging, and in recent years has focused on imaging brain function during active social exchange. Montague is broadly interested in the detailed neurobiology of social behaviour with a particular emphasis on the role of neuromodulatory systems that deliver dopamine and serotonin throughout the brain. His laboratory uses theoretical, computational, and experimental approaches to these issues. In particular, the group now employs novel approaches to functional neuroimaging, new biomarkers for mental disease, spectroscopy, real-time voltammetry, and computational simulations. Montague also directs the Roanoke Brain Study, a project aimed at understanding decision-making through the lifespan and its relationship to brain development, function, and disease. Work in the laboratory is supported by the National Institutes of Health, National Science Foundation, The Kane Family Foundation, Autism Speaks, The MacArthur Foundation, The Dana Foundation, and The Wellcome Trust.