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  • Conference paper
    Majewska P, Ribeiro Violante I, Lorenz R, De Simoni S, Sharp Det 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
  • Journal article
    Scott G, Fagerholm ED, Mutoh H, Leech R, Sharp DJ, Shew WL, Knöpfel Tet 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.
  • Journal article
    Scott G, Hellyer PJ, Hampshire A, Leech Ret al., 2014,

    Exploring spatiotemporal network transitions in task functional MRI

    , Hum. Brain Mapp., Pages: n/a-n/a, ISSN: 1097-0193
  • Journal article
    Monti RP, Hellyer P, Sharp D, Leech R, Anagnostopoulos C, Montana Get al., 2014,

    Estimating time-varying brain connectivity networks from functional MRI time series

    , NEUROIMAGE, Vol: 103, Pages: 427-443, ISSN: 1053-8119
  • Journal article
    Hiebert NM, Vo A, Hampshire A, Owen AM, Seergobin KN, MacDonald PAet al., 2014,

    Striatum in stimulus-response learning via feedback and in decision making.

    , Neuroimage, Vol: 101, Pages: 448-457

    Cognitive deficits are recognized in Parkinson's disease. Understanding cognitive functions mediated by the striatum can clarify some of these impairments and inform treatment strategies. The dorsal striatum, a region impaired in Parkinson's disease, has been implicated in stimulus-response learning. However, most investigations combine acquisition of associations between stimuli, responses, or outcomes (i.e., learning) and expression of learning through response selection and decision enactment, confounding these separate processes. Using neuroimaging, we provide evidence that dorsal striatum does not mediate stimulus-response learning from feedback but rather underlies decision making once associations between stimuli and responses are learned. In the experiment, 11 males and 5 females (mean age 22) learned to associate abstract images to specific button-press responses through feedback in Session 1. In Session 2, they were asked to provide responses learned in Session 1. Feedback was omitted, precluding further feedback-based learning in this session. Using functional magnetic resonance imaging, dorsal striatum activation in healthy young participants was observed at the time of response selection and not during feedback, when greatest learning presumably occurs. Moreover, dorsal striatum activity increased across the duration of Session 1, peaking after most associations were well learned, and was significant during Session 2 where no feedback was provided, and therefore no feedback-based learning occurred. Preferential ventral striatum activity occurred during feedback and was maximal early in Session 1. Taken together, the results suggest that the ventral striatum underlies learning associations between stimuli and responses via feedback whereas the dorsal striatum mediates enacting decisions.
  • Journal article
    Nombela C, Rowe JB, Winder-Rhodes SE, Hampshire A, Owen AM, Breen DP, Duncan GW, Khoo TK, Yarnall AJ, Firbank MJ, Chinnery PF, Robbins TW, O'Brien JT, Brooks DJ, Burn DJ, Barker RAet al., 2014,

    Genetic impact on cognition and brain function in newly diagnosed Parkinson's disease: ICICLE-PD study

    , Brain, Vol: 137, Pages: 2743-2758, ISSN: 0006-8950

    Parkinson’s disease is associated with multiple cognitive impairments and increased risk of dementia, but the extent of these deficits varies widely among patients. The ICICLE-PD study was established to define the characteristics and prevalence of cognitive change soon after diagnosis, in a representative cohort of patients, using a multimodal approach. Specifically, we tested the ‘Dual Syndrome’ hypothesis for cognitive impairment in Parkinson’s disease, which distinguishes an executive syndrome (affecting the frontostriatal regions due to dopaminergic deficits) from a posterior cortical syndrome (affecting visuospatial, mnemonic and semantic functions related to Lewy body pathology and secondary cholinergic loss). An incident Parkinson’s disease cohort (n = 168, median 8 months from diagnosis to participation) and matched control group (n = 85) were recruited to a neuroimaging study at two sites in the UK. All participants underwent clinical, neuropsychological and functional magnetic resonance imaging assessments. The three neuroimaging tasks (Tower of London, Spatial Rotations and Memory Encoding Tasks) were designed to probe executive, visuospatial and memory encoding domains, respectively. Patients were also genotyped for three polymorphisms associated with cognitive change in Parkinson’s disease and related disorders: (i) rs4680 for COMT Val158Met polymorphism; (ii) rs9468 for MAPT H1 versus H2 haplotype; and (iii) rs429358 for APOE-ε2, 3, 4. We identified performance deficits in all three cognitive domains, which were associated with regionally specific changes in cortical activation. Task-specific regional activations in Parkinson’s disease were linked with genetic variation: the rs4680 polymorphism modulated the effect of levodopa therapy on planning-related activations in the frontoparietal network; the MAPT haplotype modulated parietal activations associated with spatial rotations; and APOE allelic varia
  • Journal article
    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
  • Journal article
    Scott G, Sharp DJ, Ramlackhansingh A, Hellyer P, Leech R, Greenwood R, Turkheimer F, Heckemann R, Matthews P, Brooks Det al., 2014,

    NEUROINFLAMMATION AND AMYLOID PATHOLOGY AFTER TBI

    , JOURNAL OF NEUROLOGY NEUROSURGERY AND PSYCHIATRY, Vol: 85, ISSN: 0022-3050
  • Conference paper
    Jenkins P, De Simoni S, Grover P, Waldman A, Sharp Det al., 2014,

    HIPPOCAMPAL CONNECTIVITY AND POST-TRAUMATIC AMNESIA

    , Meeting of the Associatiion-of-British-Neurologists, Publisher: BMJ PUBLISHING GROUP, ISSN: 0022-3050
  • Journal article
    MacFarlane JW, Payton OD, Keatley AC, Scott GPT, Pullin H, Crane RA, Smilion M, Popescu I, Curlea V, Scott TBet al., 2014,

    Lightweight aerial vehicles for monitoring, assessment and mapping of radiation anomalies

    , JOURNAL OF ENVIRONMENTAL RADIOACTIVITY, Vol: 136, Pages: 127-130, ISSN: 0265-931X

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