Publications
618 results found
Fagerholm ED, Lorenz R, Scott G, et al., 2015, Cascades and Cognitive State: Focused Attention Incurs Subcritical Dynamics, Journal of Neuroscience, Vol: 35, Pages: 4626-4634, ISSN: 1529-2401
Ghajari M, Sharp DJ, 2015, Computational analysis of white matter response to rear and lateral impacts, Pages: 229-230
Majewska P, Ribeiro Violante I, Lorenz R, et al., 2015, EEG characteristics of memory deficits in acute traumatic brain injury patients with post-traumatic amnesia, The Society of British Neurological Surgeons Meeting 2015
Kramer AH, Charaffedine R, O'Rourke BP, et al., 2015, Fidgetin-Like 2: At the heart of regeneration, Publisher: AMER SOC CELL BIOLOGY, ISSN: 1059-1524
Scott G, Fagerholm ED, Mutoh H, et al., 2014, Voltage imaging of waking mouse cortex reveals emergence of critical neuronal dynamics, The Journal of Neuroscience, Vol: 34, Pages: 16611-16620, ISSN: 0270-6474
Complex cognitive processes require neuronal activity to be coordinated across multiple scales, ranging from local microcircuits to cortex-wide networks. However, multiscale cortical dynamics are not well understood because few experimental approaches have provided sufficient support for hypotheses involving multiscale interactions. To address these limitations, we used, in experiments involving mice, genetically encoded voltage indicator imaging, which measures cortex-wide electrical activity at high spatiotemporal resolution. Here we show that, as mice recovered from anesthesia, scale-invariant spatiotemporal patterns of neuronal activity gradually emerge. We show for the first time that this scale-invariant activity spans four orders of magnitude in awake mice. In contrast, we found that the cortical dynamics of anesthetized mice were not scale invariant. Our results bridge empirical evidence from disparate scales and support theoretical predictions that the awake cortex operates in a dynamical regime known as criticality. The criticality hypothesis predicts that small-scale cortical dynamics are governed by the same principles as those governing larger-scale dynamics. Importantly, these scale-invariant principles also optimize certain aspects of information processing. Our results suggest that during the emergence from anesthesia, criticality arises as information processing demands increase. We expect that, as measurement tools advance toward larger scales and greater resolution, the multiscale framework offered by criticality will continue to provide quantitative predictions and insight on how neurons, microcircuits, and large-scale networks are dynamically coordinated in the brain.
Monti RP, Hellyer P, Sharp D, et al., 2014, Estimating time-varying brain connectivity networks from functional MRI time series, NEUROIMAGE, Vol: 103, Pages: 427-443, ISSN: 1053-8119
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- Citations: 114
Jenkins P, De Simoni S, Grover P, et al., 2014, HIPPOCAMPAL CONNECTIVITY AND POST-TRAUMATIC AMNESIA, Meeting of the Associatiion-of-British-Neurologists, Publisher: BMJ PUBLISHING GROUP, ISSN: 0022-3050
Scott G, Sharp DJ, Ramlackhansingh A, et al., 2014, NEUROINFLAMMATION AND AMYLOID PATHOLOGY AFTER TBI, JOURNAL OF NEUROLOGY NEUROSURGERY AND PSYCHIATRY, Vol: 85, ISSN: 0022-3050
Sharp DJ, 2014, The association of traumatic brain injury with rate of progression of cognitive and functional impairment in a population-based cohort of Alzheimer's disease: the Cache County dementia progression study by Gilbert <i>et</i> <i>al</i>. Late effects of traumatic brain injury on dementia progression, INTERNATIONAL PSYCHOGERIATRICS, Vol: 26, Pages: 1591-1592, ISSN: 1041-6102
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- Citations: 6
Jilka SR, Scott G, Ham T, et al., 2014, Damage to the Salience Network and Interactions with the Default Mode Network, JOURNAL OF NEUROSCIENCE, Vol: 34, Pages: 10798-10807, ISSN: 0270-6474
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- Citations: 156
Lin C, Kayali O, Morozov EV, et al., 2014, Influence of fibre type on flexural behaviour of self-compacting fibre reinforced cementitious composites, CEMENT & CONCRETE COMPOSITES, Vol: 51, Pages: 27-37, ISSN: 0958-9465
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- Citations: 42
O'Rourke BP, Gomez-Ferreria MA, Berk RH, et al., 2014, Cep192 Controls the Balance of Centrosome and Non-Centrosomal Microtubules during Interphase, PLOS ONE, Vol: 9, ISSN: 1932-6203
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- Citations: 28
Leech R, Scott G, Carhart-Harris R, et al., 2014, Spatial Dependencies between Large-Scale Brain Networks, PLoS ONE, Vol: 9
<p>Functional neuroimaging reveals both increases (task-positive) and decreases (task-negative) in neural activation with many tasks. Many studies show a <italic>temporal</italic> relationship between task positive and task negative networks that is important for efficient cognitive functioning. Here we provide evidence for a <italic>spatial</italic> relationship between task positive and negative networks. There are strong spatial similarities between many reported task negative brain networks, termed the default mode network, which is typically assumed to be a spatially fixed network. However, this is not the case. The spatial structure of the DMN varies depending on what specific task is being performed. We test whether there is a fundamental <italic>spatial</italic> relationship between task positive and negative networks. Specifically, we hypothesize that the distance between task positive and negative voxels is consistent despite different spatial patterns of activation and deactivation evoked by different cognitive tasks. We show significantly reduced variability in the distance between within-condition task positive and task negative voxels than across-condition distances for four different sensory, motor and cognitive tasks - implying that deactivation patterns are spatially dependent on activation patterns (and <italic>vice versa</italic>), and that both are modulated by specific task demands. We also show a similar relationship between positively and negatively correlated networks from a third ‘rest’ dataset, in the absence of a specific task. We propose that this spatial relationship may be the macroscopic analogue of microscopic neuronal organization reported in sensory cortical systems, and that this organization may reflect homeostatic plasticity necessary for efficient brain function.</p>
Nigmatullina Y, Hellyer PM, Nachev P, et al., 2014, The neuroanatomical correlates of vestibular adaptation in ballet dancers, Joint Congress of European Neurology, Publisher: SPRINGER HEIDELBERG, Pages: S190-S191, ISSN: 0340-5354
Kwok H-T, Baxter D, DeFelice J, et al., 2014, The neuropathology of blast traumatic brain injury in a porcine polytrauma model, BRAIN INJURY, Vol: 28, Pages: 779-780, ISSN: 0269-9052
Baker S, Williams H, Sharp D, et al., 2014, Sports-related concussion and diffusion tensor imaging findings in rugby players, BRAIN INJURY, Vol: 28, Pages: 686-686, ISSN: 0269-9052
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- Citations: 1
Nigmatullina Y, Hellyer PM, Nachev P, et al., 2014, The neuroanatomical correlates of vestibular adaptation in ballet dancers, Joint Congress of European Neurology, Publisher: WILEY-BLACKWELL, Pages: 278-278, ISSN: 1351-5101
Simmonds AJ, Wise RJS, Collins C, et al., 2014, Parallel systems in the control of speech, HUMAN BRAIN MAPPING, Vol: 35, Pages: 1930-1943, ISSN: 1065-9471
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- Citations: 19
Charafeddine R, Makdisi J, Friedman J, et al., 2014, FIDGETIN-LIKE 2: A NOVEL MICROTUBULE-BASED REGULATOR OF WOUND HEALING, Publisher: WILEY-BLACKWELL, Pages: A34-A34, ISSN: 1067-1927
Sharp DJ, Scott G, Leech R, 2014, Network dysfunction after traumatic brain injury, NATURE REVIEWS NEUROLOGY, Vol: 10, Pages: 156-166, ISSN: 1759-4758
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- Citations: 427
Ham TE, Bonnelle V, Hellyer P, et al., 2014, The neural basis of impaired self-awareness after traumatic brain injury, BRAIN, Vol: 137, Pages: 586-597, ISSN: 0006-8950
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- Citations: 83
Hellyer PJ, Shanahan MP, Scott G, et al., 2014, The control of global brain dynamics: opposing actions of frontoparietal control and default mode networks on attention, Journal of Neuroscience, Vol: 34, Pages: 451-461, ISSN: 1529-2401
Understanding how dynamic changes in brain activity control behavior is a major challenge of cognitive neuroscience. Here, we consider the brain as a complex dynamic system and define two measures of brain dynamics: the synchrony of brain activity, measured by the spatial coherence of the BOLD signal across regions of the brain; and metastability, which we define as the extent to which synchrony varies over time. We investigate the relationship among brain network activity, metastability, and cognitive state in humans, testing the hypothesis that global metastability is “tuned” by network interactions. We study the following two conditions: (1) an attentionally demanding choice reaction time task (CRT); and (2) an unconstrained “rest” state. Functional MRI demonstrated increased synchrony, and decreased metastability was associated with increased activity within the frontoparietal control/dorsal attention network (FPCN/DAN) activity and decreased default mode network (DMN) activity during the CRT compared with rest. Using a computational model of neural dynamics that is constrained by white matter structure to test whether simulated changes in FPCN/DAN and DMN activity produce similar effects, we demonstate that activation of the FPCN/DAN increases global synchrony and decreases metastability. DMN activation had the opposite effects. These results suggest that the balance of activity in the FPCN/DAN and DMN might control global metastability, providing a mechanistic explanation of how attentional state is shifted between an unfocused/exploratory mode characterized by high metastability, and a focused/constrained mode characterized by low metastability.
Cutfield NJ, Scott G, Waldman AD, et al., 2014, Visual and proprioceptive interaction in patients with bilateral vestibular loss, NEUROIMAGE-CLINICAL, Vol: 4, Pages: 274-282, ISSN: 2213-1582
Following bilateral vestibular loss (BVL) patients gradually adapt to the loss of vestibular input and rely more on other sensory inputs. Here we examine changes in the way proprioceptive and visual inputs interact. We used functional magnetic resonance imaging (fMRI) to investigate visual responses in the context of varying levels of proprioceptive input in 12 BVL subjects and 15 normal controls. A novel metal-free vibrator was developed to allow vibrotactile neck proprioceptive input to be delivered in the MRI system. A high level (100 Hz) and low level (30 Hz) control stimulus was applied over the left splenius capitis; only the high frequency stimulus generates a significant proprioceptive stimulus. The neck stimulus was applied in combination with static and moving (optokinetic) visual stimuli, in a factorial fMRI experimental design. We found that high level neck proprioceptive input had more cortical effect on brain activity in the BVL patients. This included a reduction in visual motion responses during high levels of proprioceptive input and differential activation in the midline cerebellum. In early visual cortical areas, the effect of high proprioceptive input was present for both visual conditions but in lateral visual areas, including V5/MT, the effect was only seen in the context of visual motion stimulation. The finding of a cortical visuo-proprioceptive interaction in BVL patients is consistent with behavioural data indicating that, in BVL patients, neck afferents partly replace vestibular input during the CNS-mediated compensatory process. An fMRI cervico-visual interaction may thus substitute the known visuo-vestibular interaction reported in normal subject fMRI studies. The results provide evidence for a cortical mechanism of adaptation to vestibular failure, in the form of an enhanced proprioceptive influence on visual processing. The results may provide the basis for a cortical mechanism involved in proprioceptive substitution of vestibular func
Leech R, Sharp DJ, 2014, The role of the posterior cingulate cortex in cognition and disease, BRAIN, Vol: 137, Pages: 12-32, ISSN: 0006-8950
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- Citations: 1374
Sharp DJ, 2014, Mitosis Methods and Protocols Preface, MITOSIS: METHODS AND PROTOCOLS, Editors: Sharp, Publisher: HUMANA PRESS INC, Pages: V-V, ISBN: 978-1-4939-0328-3
Lin C, Kayali O, Morozov EV, et al., 2014, USAGE OF HIGH VOLUME FLY ASH IN SELF-CONSOLIDATING STRAIN-HARDENING CEMENTITIOUS COMPOSITES, 3rd International Symposium on Design, Performance and Use of Self-Consolidating Concrete (SCC-China), Publisher: R I L E M PUBLICATIONS, Pages: 251-251, ISSN: 1461-1147
Deligianni F, Varoquaux G, Thirion B, et al., 2013, A Framework for Inter-Subject Prediction of Functional Connectivity From Structural Networks, IEEE TRANSACTIONS ON MEDICAL IMAGING, Vol: 32, Pages: 2200-2214, ISSN: 0278-0062
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- Citations: 23
Carhart-Harris RL, Leech R, Erritzoe D, et al., 2013, Functional Connectivity Measures After Psilocybin Inform a Novel Hypothesis of Early Psychosis, SCHIZOPHRENIA BULLETIN, Vol: 39, Pages: 1343-1351, ISSN: 0586-7614
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- Citations: 135
Baxter D, Sharp DJ, Feeney C, et al., 2013, Pituitary Dysfunction after Blast Traumatic Brain Injury: The UK BIOSAP Study, ANNALS OF NEUROLOGY, Vol: 74, Pages: 527-536, ISSN: 0364-5134
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- Citations: 59
Nigmatullina Y, Hellyer PJ, Nachev P, et al., 2013, The Neuroanatomical Correlates of Training-Related Perceptuo-Reflex Uncoupling in Dancers, Cerebral Cortex, Vol: 25, Pages: 554-562
Sensory input evokes low-order reflexes and higher-order perceptual responses. Vestibular stimulation elicits vestibular-ocular reflex (VOR) and self-motion perception (e.g., vertigo) whose response durations are normally equal. Adaptation to repeated whole-body rotations, for example, ballet training, is known to reduce vestibular responses. We investigated the neuroanatomical correlates of vestibular perceptuo-reflex adaptation in ballet dancers and controls. Dancers' vestibular-reflex and perceptual responses to whole-body yaw-plane step rotations were: (1) Briefer and (2) uncorrelated (controls' reflex and perception were correlated). Voxel-based morphometry showed a selective gray matter (GM) reduction in dancers' vestibular cerebellum correlating with ballet experience. Dancers' vestibular cerebellar GM density reduction was related to shorter perceptual responses (i.e. positively correlated) but longer VOR duration (negatively correlated). Contrastingly, controls' vestibular cerebellar GM density negatively correlated with perception and VOR. Diffusion-tensor imaging showed that cerebral cortex white matter (WM) microstructure correlated with vestibular perception but only in controls. In summary, dancers display vestibular perceptuo-reflex dissociation with the neuronatomical correlate localized to the vestibular cerebellum. Controls' robust vestibular perception correlated with a cortical WM network conspicuously absent in dancers. Since primary vestibular afferents synapse in the vestibular cerebellum, we speculate that a cerebellar gating of perceptual signals to cortical regions mediates the training-related attenuation of vestibular perception and perceptuo-reflex uncoupling.
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