Peter J Hellyer

Peter J Hellyer
King's College London · Neuroimaging

BSc, MRes, PhD

About

83
Publications
60,763
Reads
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3,952
Citations
Citations since 2016
59 Research Items
3694 Citations
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20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
Additional affiliations
September 2014 - October 2015
King's College London
Position
  • Resarch Associate
November 2011 - November 2014
Imperial College London
Position
  • PhD Student

Publications

Publications (83)
Article
Neurological conditions present with cognitive impairment that greatly affects the quality of life of the patients and should be routinely evaluated. However, it can be difficult to detect and impractical to monitor with classic in person cognitive assessment due to limitations of sensitivity, scalability and cost. Internet- and app-based tools for...
Article
Full-text available
For most neuroimaging questions the range of possible analytic choices makes it unclear how to evaluate conclusions from any single analytic method. One possible way to address this issue is to evaluate all possible analyses using a multiverse approach, however, this can be computationally challenging and sequential analyses on the same data can co...
Article
Full-text available
Background Preliminary evidence has highlighted a possible association between severe COVID-19 and persistent cognitive deficits. Further research is required to confirm this association, determine whether cognitive deficits relate to clinical features from the acute phase or to mental health status at the point of assessment, and quantify rate of...
Preprint
Full-text available
The COVID-19 pandemic represents a unique context for studying the spread of conspiratorial beliefs within the general population and their role in mediating compliance with government guidance. Here, we apply multivariate and machine learning methods to analyse data from tens of thousands of members of the British public at 6-monthly timepoints du...
Article
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The ability to monitor one's behaviour is frequently impaired following TBI, impacting on patients' rehabilitation. Inaccuracies in judgement or self-reflection of one's performance provides a useful marker of metacognition. However, metacognition is rarely measured during routine neuropsychology assessments and how it varies across cognitive domai...
Article
Full-text available
Background There is widespread concern regarding how the COVID-19 pandemic has affected mental health. Emerging meta-analyses suggest that the impact on anxiety/depression may have been transient, but much of the included literature has major methodological limitations. Addressing this topic rigorously requires longitudinal data of sufficient scope...
Article
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Recent studies indicate that COVID-19 infection can lead to serious neurological consequences in a small percentage of individuals. However, in the months following acute illness, many more suffer from fatigue, low motivation, disturbed mood, poor sleep and cognitive symptoms, colloquially referred to as 'brain fog'. But what about individuals who...
Article
Full-text available
Objective To compare cognitive testing scores in neurosurgeons and aerospace engineers to help settle the age old argument of which phrase—“It’s not brain surgery” or “It’s not rocket science”—is most deserved. Design International prospective comparative study. Setting United Kingdom, Europe, the United States, and Canada. Participants 748 peop...
Article
There has been considerable speculation regarding how people cope during the COVID-19 pandemic; however, surveys requiring selection from prespecified answers are limited by researcher views and may overlook the most effective measures. Here, we apply an unbiased approach that learns from people's collective lived experiences through the applicatio...
Poster
Full-text available
Introduction: Patients with minor stroke are often discharged from the hyperacute stroke unit (HASU) without therapy or nursing follow-up. During their admission they are given information on their stroke, medication and secondary prevention. Stroke survivors tell us information provision is poor and undetected hidden impairments have significant,...
Poster
Full-text available
Background And Aims: Post stroke cognitive impairment is common, affecting recovery and quality of life. UK Clinical Guidelines state that everyone should be screened for cognitive impairment following stroke. Commonly used screening tools are often not sensitive enough to pick up subtle higher-level difficulties that may impact return to work and...
Preprint
The ability to monitor one's behaviour is frequently impaired following TBI, impacting on patients' rehabilitation and resulting in poor functional outcomes. Inaccuracies in the judgement or self-reflection of one’s performance provides a useful marker of metacognition. However, cognition is complex, comprising distinct sub-domains; how metacogniti...
Article
Full-text available
The COVID-19 pandemic (including lockdown) is likely to have had profound but diverse implications for mental health and well-being, yet little is known about individual experiences of the pandemic (positive and negative) and how this relates to mental health and well-being, as well as other important contextual variables. Here, we analyse data sam...
Preprint
Full-text available
Recent studies indicate that COVID-19 infection can lead to serious neurological consequences in a small percentage of individuals. However, in the months following acute illness, many more suffer from fatigue, low motivation, disturbed mood, poor sleep and cognitive symptoms, colloquially referred to as 'brain fog'. But what about individuals who...
Article
Full-text available
Background There is growing concern about possible cognitive consequences of COVID-19, with reports of ‘Long COVID’ symptoms persisting into the chronic phase and case studies revealing neurological problems in severely affected patients. However, there is little information regarding the nature and broader prevalence of cognitive problems post-inf...
Article
Full-text available
This study examined post-traumatic stress disorder (PTSD) symptoms in 13 049 survivors of suspected or confirmed COVID-19, from the UK general population, as a function of severity and hospital admission status. Compared with mild COVID-19, significantly elevated rates of PTSD symptoms were identified in those requiring medical support at home (eff...
Article
Full-text available
The relationship between biomechanical forces and neuropathology is key to understanding traumatic brain injury. White matter tracts are damaged by high shear forces during impact, resulting in axonal injury, a key determinant of long-term clinical outcomes. However, the relationship between biomechanical forces and patterns of white matter injurie...
Article
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Vestibular dysfunction, causing dizziness and imbalance, is a common yet poorly understood feature in patients with TBI. Damage to the inner ear, nerve, brainstem, cerebellum and cerebral hemispheres may all affect vestibular functioning, hence, a multi-level assessment—from reflex to perception—is required. In a previous report, postural instabili...
Preprint
Full-text available
A bstract For most neuroimaging questions the huge range of possible analytic choices leads to the possibility that conclusions from any single analytic approach may be misleading. Examples of possible choices include the motion regression approach used and smoothing and threshold factors applied during the processing pipeline. Although it is possi...
Preprint
Full-text available
Case studies have revealed neurological problems in severely affected COVID-19 patients. However, there is little information regarding the nature and broader prevalence of cognitive problems post-infection or across the full spread of severity. We analysed cognitive test data from 84,285 Great British Intelligence Test participants who completed a...
Preprint
Full-text available
How has the Covid-19 pandemic affected mental health? What are the most common positives and negatives? How do population variables mediate the impact on mood and behaviour? Who is most at risk of adverse consequences? Which pragmatic measures can help? We address these questions in a data-driven manner by applying multivariate, machine-learning an...
Preprint
Full-text available
We developed two novel self-ordered switching (SOS) fMRI paradigms to investigate how human behaviour and underlying network resources are optimised when learning to perform complex tasks with multiple goals. SOS was performed with detailed feedback and minimal pretraining (study 1) or with minimal feedback and substantial pretraining (study 2). In...
Article
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The use of machine learning (ML) algorithms has significantly increased in neuroscience. However, from the vast extent of possible ML algorithms, which one is the optimal model to predict the target variable? What are the hyperparameters for such a model? Given the plethora of possible answers to these questions, in the last years, automated ML (au...
Article
The outcomes from spinal nerve decompression surgery are highly variable with a sizable proportion of elderly foraminal stenosis patients not regaining good pain relief. A better understanding of nerve root compression before and following decompression surgery and whether these changes are mirrored by improvements in symptoms may help to improve c...
Preprint
The use of machine learning (ML) algorithms has significantly increased in neuroscience. However, from the vast extent of possible ML algorithms, which one is the optimal model to predict the target variable? What are the hyperparameters for such a model? Given the plethora of possible answers to these questions, in the last years, automated machin...
Article
Full-text available
In many clinical and scientific situations the optimal neuroimaging sequence may not be known prior to scanning and may differ for each individual being scanned, depending on the exact nature and location of abnormalities. Despite this, the standard approach to data acquisition, in such situations, is to specify the sequence of neuroimaging scans p...
Article
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Age-related degenerative changes in the lumbar spine frequently result in nerve root compression causing severe pain and disability. Given the increasing incidence of lumbar spinal disorders in the aging population and the discrepancies between the use of current diagnostic imaging tools and clinical symptoms, novel methods of nerve root assessment...
Article
The concept of "emergence" has become commonplace in the modelling of complex systems, both natural and man-made; a functional property" emerges" from a system when it cannot be readily explained by the properties of the system's sub-units. A bewildering array of adaptive and sophisticated behaviours can be observed from large ensembles of elementa...
Article
Decreases in cortical volume (CV), thickness (CT) and surface area (SA) have been reported in individuals with schizophrenia by in vivo MRI studies. However, there are few studies that examine these cortical measures as potential biomarkers of treatment resistance (TR) and treatment response (NTR) in schizophrenia. This study used structural MRI to...
Article
Full-text available
In many clinical and scientific situations the optimal neuroimaging sequence may not be known prior to scanning and may differ for each individual being scanned, depending on the exact nature and location of abnormalities. Despite this, the standard approach to data acquisition, in such situations, is to specify the sequence of neuroimaging scans p...
Article
Low-dimensional yet rich dynamics often emerge in the brain. Examples include oscillations and chaotic dynamics during sleep, epilepsy, and voluntary movement. However, a general mechanism for the emergence of low dimensional dynamics remains elusive. Here, we consider Wilson-Cowan networks and demonstrate through numerical and analytical work that...
Article
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This study focuses on microstructural changes that occur within the mammalian lung when subject to blast and how these changes influence strain distributions within the tissue. Shock tube experiments were performed to generate the blast injured specimens (cadaveric Sprague-Dawley rats). Blast overpressures of 100 and 180 kPa were studied. Synchrotr...
Article
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Traumatic brain injury often produces executive dysfunction. This characteristic cognitive impairment often causes long-term problems with behaviour and personality. Frontal lobe injuries are associated with executive dysfunction, but it is unclear how these injuries relate to corticostriatal interactions that are known to play an important role in...
Article
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Purpose: Diffusion tensor imaging (DTI) has shown promise in the measurement of peripheral nerve integrity, although the optimal way to apply the technique for the study of lumbar spinal nerves is unclear. The aims of this study are to use an improved DTI acquisition to investigate lumbar nerve root integrity and correlate this with functional mea...
Article
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Author summary In recent years, there has been growing interest in using computational models based on the human structural connectome to better understand the brain. These simulations typically investigate spontaneous neural dynamics, in the absence of tasks, sensory input or motor output. Here, we take a different approach, embodying a computatio...
Data
Power-law scaling in avalanche dynamics associated with local homeostatic plasticity in neural dynamics. Cascade Size (i.e. the number of regions of the model involved in a putative neural avalanche). Here we present the negative log-likelihood of a perfect power-law fit of neural dynamics. Red, Orange, Green and Blue Markers represent the same reg...
Data
Power-law scaling in avalanche dynamics associated with phase-transition in the simulated neural dynamics. Top: cascade Size (i.e. the number of regions of the model involved in a putative neural avalanche) Bottom: cascade Length (i.e. the distribution of the lengths of each putative neural avalanche). Here we present Kappa (relative to a perfect p...
Data
Behavioral dynamics within the non-plastic and local homeostasis forms of the agent model. Models were run for 2000 epochs, and the movement of the model was plotted into real coordinate space (A) for the Non-plastic (Green trails), Local Homeostatic (Blue Trails) and Combined local and macroscopic (Red Trails) Model. (TIF)
Poster
Full-text available
Schizophrenia is a severe psychiatric condition characterized by symptoms such as hallucinations, paranoia, and delusions. Standard treatment for schizophrenia is effective for the majority patients however approximately 33% of patients remain treatment resistant (TR). It has been suggested that the underlying neurobiological mechanism for TR may b...
Article
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Objective: Traumatic brain injury (TBI) is a common disabling condition with limited treatment options. Diffusion tensor imaging (DTI) measures recovery of axonal injury in white matter (WM) tracts after TBI. Growth hormone deficiency (GHD) after TBI may impair axonal and neuropsychological recovery, and serum IGF-I may mediate this effect. We con...
Article
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L-[1-¹¹C]leucine PET can be used to measure in vivo protein synthesis in the brain. However, the relationship between regional protein synthesis and on-going neural dynamics is unclear. We use a graph theoretical approach to examine the relationship between cerebral protein synthesis (rCPS) and both static and dynamical measures of functional conne...
Article
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An exciting avenue of neuroscientific research involves quantifying the time-varying properties of functional connectivity networks. As a result, many methods have been proposed to estimate the dynamic properties of such networks. However, one of the challenges associated with such methods involves the interpretation and visualization of high-dimen...
Article
Traumatic brain injury can lead to the neurodegenerative disease chronic traumatic encephalopathy. This condition has a clear neuropathological definition but the relationship between the initial head impact and the pattern of progressive brain pathology is poorly understood. We test the hypothesis that mechanical strain and strain rate are greates...
Article
Full-text available
A frontoparietal network of brain regions is often implicated in both auditory and visual information processing. Although it is possible that the same set of multimodal regions subserves both modalities, there is increasing evidence that there is a differentiation of sensory function within frontoparietal cortex. Magnetic resonance imaging (MRI) i...
Article
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In recent years, there have been many computational models exploring how spontaneous neural dynamics arise out of the brain's structural connectome. Most of these models have focused on the resting state (with no external input) or investigate the effects of simple sensory inputs. However, neural systems exist to process incoming information from t...
Article
Full-text available
Significance Lysergic acid diethylamide (LSD), the prototypical “psychedelic,” may be unique among psychoactive substances. In the decades that followed its discovery, the magnitude of its effect on science, the arts, and society was unprecedented. LSD produces profound, sometimes life-changing experiences in microgram doses, making it a particular...
Article
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Objective: To image β-amyloid (Aβ) plaque burden in long-term survivors of traumatic brain injury (TBI), test whether traumatic axonal injury and Aβ are correlated, and compare the spatial distribution of Aβ to Alzheimer disease (AD). Methods: Patients 11 months to 17 years after moderate-severe TBI underwent (11)C-Pittsburgh compound B ((11)C-P...
Article
Full-text available
Traumatic brain injury can trigger chronic neuroinflammation, which may predispose to neurodegeneration. Animal models and human pathological studies demonstrate persistent inflammation in the thalamus associated with axonal injury, but this relationship has never been shown in vivo. Using [ 11 C]-PK11195 positron emission tomography, a marker of m...