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Head injury
030 Brain imaging studies of self processing
  1. S Laureys

    Author information: Steven Laureys graduated as a Medical Doctor from the Vrije Universiteit Brussel, Belgium, in 1993. While specialising in neurology he entered a research career and obtained his M.Sc. in Pharmaceutical Medicine working on pain and stroke using in vivo microdialysis and diffusion MRI in the rat (1997). Drawn by functional neuroimaging, he moved to the Cyclotron Research Center at the University of Liège, Belgium, where he obtained his Ph.D. studying residual brain function in the vegetative state in 2000. He is board-certified in neurology (1998) and in end-of-life and palliative medicine (2004). He edited The Boundaries of Consciousness (Elsevier 2005) and co-edited The Neurology of Consciousness (Academic Press 2009). He currently leads the Coma Science Group at the Cyclotron Research Centre of the University of Liège, Belgium. He is clinical professor of neurology, at the Liège University Hospital and Senior Research Associate at the National Fund for Scientific Research. Since 2008, Laureys is chair of the European Neurological Society Subcommittee on Coma and Disorders of Consciousness [2] and since 2009 he is invited professor at the Royal Academy of Belgium. His team assesses the recovery of neurological disability and of neuronal plasticity in severely brain damaged patients with altered states of consciousness by means of multimodal functional neuroimaging. It aims at characterising the brain structure and the residual cerebral function in patients who survive a severe brain injury: patients in coma, vegetative state, minimally conscious state and locked in syndrome. The importance of this project is twofold. First, these patients represent a problem in terms of diagnosis, prognosis, treatment and daily management. Second, these patients offer the opportunity to explore human consciousness, which is presently one major conundrum neurosciences have to solve. Indeed, these patients present a complete, nearly graded, range of conscious states from unconsciousness (coma) to full awareness (locked-in syndrome). This research confronts clinical expertise and bedside behavioural evaluation of altered states of consciousness.

Abstract

Abstract: Recent neuroimaging and electrophysiology studies are illuminating the relationships between awareness and: (i) global brain function; (ii) regional brain function; (iii) changes in functional connectivity; and (iv) primary vs associative cortical activation in response to external stimulation. Is awareness lost when overall cortical activity falls below a certain threshold? In the vegetative state, global metabolic activity decreases to about 50% of normal levels—similar to what is observed in sleep, anaesthesia and coma. However, it seems that some areas in the brain are more important than others for consciousness. Voxel-based statistical analyses have identified a dysfunction in a wide frontoparietal network encompassing the polymodal associative cortices. Consciousness seems not exclusively related to the activity in the frontoparietal network but, as importantly, to the functional connectivity within this network and with the thalami. In addition to measuring resting brain function and connectivity, neuroimaging studies have identified which brain areas still “activate” during external stimulation in vegetative patients. Studies using external (noxious or auditory) stimulation showed robust activation in subcortical and primary sensory cortex which was however isolated and dissociated from the frontoparietal cortical network. Of clinical importance, this knowledge now permits to improve the diagnosis of patients with disorders of consciousness, which remains very challenging at the bedside. Current technology now also permits to show command-specific changes in EEG or fMRI signals providing motor-independent evidence of conscious thoughts. Such brain computer interfaces now permit communication via voluntary EEG or fMRI control, enabling locked-in patients to control their surroundings and giving a voice to minimally conscious state patients. http://www.comascience.org with state-of-the-art multimodal imaging combining the information from positron emission tomography (PET), functional MRI, structural MRI, electroencephalography (EEG), event related potential (ERP) and transcranial magnetic stimulation (TMS) data.

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