Papers by David McGonigle
Transcranial modulation of brain oscillatory responses: A concurrent tDCS–MEG investigation
NeuroImage, 2015
Despite the increasing use of transcranial direct current stimulation (tDCS), the physiological m... more Despite the increasing use of transcranial direct current stimulation (tDCS), the physiological mechanisms underlying its effects are still largely unknown. One approach to directly investigate the effects of the neuromodulation technique on the brain is to integrate tDCS with non-invasive neuroimaging in humans. To provide new insight into the neurobiology of the method, DC stimulation (1mA, 600s) was applied concurrently with Magnetoencephalography (MEG), while participants engaged in a visuomotor task before, during and after the period of tDCS. Responses in the motor beta band (15-30Hz) and visual gamma band (30-80Hz) were localised using Synthetic Aperture Magnetometry (SAM). The resulting induced and evoked oscillatory responses were subsequently analysed. A statistically significant reduction of average power in the visual gamma band was observed for anodal compared to sham stimulation. The magnitude of motor evoked responses was also found to be significantly modulated by anodal stimulation. These results demonstrate that MEG can be used to derive inferences on the cortical mechanisms of tDCS.
Nips, 2006
Structural equation models can be seen as an extension of Gaussian belief networks to cyclic grap... more Structural equation models can be seen as an extension of Gaussian belief networks to cyclic graphs, and we show they can be understood generatively as the model for the joint distribution of long term average equilibrium activity of Gaussian dynamic belief networks. Most use of structural equation models in fMRI involves postulating a particular structure and comparing learnt parameters across different groups. In this paper it is argued that there are situations where priors about structure are not firm or exhaustive, and given sufficient data, it is worth investigating learning network structure as part of the approach to connectivity analysis. First we demonstrate structure learning on a toy problem. We then show that for particular fMRI data the simple models usually assumed are not supported. We show that is is possible to learn sensible structural equation models that can provide modelling benefits, but that are not necessarily going to be the same as a true causal model, and suggest the combination of prior models and learning or the use of temporal information from dynamic models may provide more benefits than learning structural equations alone.
Ambiguity in Motor Selection: An fMRI Test of Appropriate Actions
Stimulating somatosensory psychophysics: a double-blind, sham-controlled study of the neurobiological mechanisms of tDCS
Frontiers in Cellular Neuroscience, 2015
The neuromodulation technique transcranial direct current stimulation (tDCS) is thought to produc... more The neuromodulation technique transcranial direct current stimulation (tDCS) is thought to produce its effects on behavior by altering cortical excitability. Although the mechanisms underlying the observed effects are thought to rely on the balance of excitatory and inhibitory neurotransmission, the physiological principles of the technique are not completely understood. In this study, we examine the influence of tDCS on vibrotactile adaptation, using a simple amplitude discrimination paradigm that has been shown to exhibit modifications in performance due to changes in inhibitory neurotransmission. Double-blind tDCS (Anodal/Sham) of 1 mA was delivered for 600 s to electrodes positioned in a somatosensory/contralateral orbit montage. Stimulation was applied as part of a pre/post design, between blocks of the behavioral tasks. In accordance with previous work, results obtained before the application of tDCS indicated that amplitude discrimination thresholds were significantly worsened during adaptation trials, compared to those achieved at baseline. However, tDCS failed to modify amplitude discrimination performance. Using a Bayesian approach, this finding was revealed to constitute substantial evidence for the null hypothesis. The failure of DC stimulation to alter vibrotactile adaptation thresholds is discussed in the context of several factors that may have confounded the induction of changes in cortical plasticity.
INVESTIGATING AUTISTIC TRAITS AND SIMPLE SENSORY PROCESSING
Journal of Neurology, Neurosurgery & Psychiatry, 2014
Linking GABA to Tactile Function in ASD: A Pilot Magnetic Resonance Spectroscopy (MRS) Study
Background: Sensory processing difficulties are a prevalent but poorly understood aspect of the b... more Background: Sensory processing difficulties are a prevalent but poorly understood aspect of the behavioural presentation of Autism Spectrum Disorder (ASD). Recent work from post-mortem and animal studies suggests that a deficit in cortical inhibitory transmission may underlie and explain some aspects of these symptoms. To date, however, no research has yet substantiated this proposal by demonstrating that neurobiological measures of cortical inhibitory deficits are connected to sensory symptoms observed behaviourally. In this study we combine tactile psychophysics and non-invasive measurements of the inhibitory neurotransmitter GABA (using Magnetic Resonance Spectroscopy; MRS) to measure and quantify aspects of atypical touch sensitivity in ASD. Objectives: This pilot study investigates two hypotheses: (1) The performance of participants with ASD on a tactile discrimination task will not be affected by the presence of a prior adapting stimulus – a task thought to be crucially relian...
Exploring the Sensory Symptoms in Adults with ASD Through Self-Report
Background: The Diagnostic Interview for Social and Communication Disorders (DISCO) is a semi-str... more Background: The Diagnostic Interview for Social and Communication Disorders (DISCO) is a semi-structured parent interview that assesses the broad range of symptoms present in individuals with ASD, including the presence of sensory features. Research using the DISCO has reported that sensory features are reported in a high percentage of individuals with ASD. Sensory atypicalities are widely present in individuals with ASD but frequency estimates vary according to type of report and tool used. The DISCO differs from other techniques, such as the Sensory Profile, as it is based on sensory modalities. Objectives: The objective was to assess the frequency of self-reported sensory atypicalities in high functioning adults using a new questionnaire developed from the DISCO. The association between responding to this questionnaire and responding to the Sensory Profile was analysed. The research also analysed the association between responses to the new sensory questionnaire responses and res...
OF NEUROPHYSIOLOGICAL TIME SERIES
Test-retest reliability in fMRI: Or how I learned to stop worrying and love the variability
NeuroImage, Jan 15, 2012
This paper briefly recounts the details of one of the first studies of whole brain, single subjec... more This paper briefly recounts the details of one of the first studies of whole brain, single subject variability in functional Magnetic Resonance Imaging (fMRI). In this paper I will not attempt to provide an overview of fMRI reliability, but will instead revisit the choices we made in performing our experiment as we did.
Calebrain: A harmonisation project for multi-centre structural and functional MRI
Moment-to-moment gastric sensation during intermittent distension is determined primarily by volume, rather than pressure or tension
Blind imagination'': Brain activation after loss of the mind's eye
Current practice in the use of MEGA-PRESS spectroscopy for the detection of GABA
NeuroImage, 2013
There is increasing interest in the use of edited proton magnetic resonance spectroscopy for the ... more There is increasing interest in the use of edited proton magnetic resonance spectroscopy for the detection of GABA in the human brain. At a recent meeting held at Cardiff University, a number of spectroscopy groups met to discuss the acquisition, analysis and interpretation of GABA-edited MR spectra. This paper aims to set out the issues discussed at this meeting, reporting areas of consensus around parameters and procedures in the field and highlighting those areas where differences remain. It is hoped that this paper can fulfill two needs, providing a summary of the current 'state-of-the-art' in the field of GABA-edited MRS at 3T using MEGA-PRESS and a basic guide to help researchers new to the field to avoid some of the pitfalls inherent in the acquisition and processing of edited MRS for GABA.
Neuroimage, 2000
The results from a single functional magnetic resonance imaging session are typically reported as... more The results from a single functional magnetic resonance imaging session are typically reported as indicative of the subject's functional neuroanatomy. Underlying this interpretation is the implicit assumption that there are no responses specific to that particular session, i.e., that the potential variability of response between sessions is negligible. The present study sought to examine this assumption empirically. A total of 99 sessions, comprising 33 repeats of simple motor, visual, and cognitive paradigms, were collected over a period of 2 months on a single male subject. For each paradigm, the inclusion of session-by-condition interactions explained a significant amount of error variance (P < 0.05 corrected for multiple comparisons) over a model assuming a common activation magnitude across all sessions. However, many of those voxels displaying significant session-by-condition interactions were not seen in a multisession fixed-effects analysis of the same data set; i.e., they were not activated on average across all sessions. Most voxels that were both significantly variable and activated on average across all sessions did not survive a randomeffects analysis (modeling between-session variance). We interpret our results as demonstrating that correct inference about subject responses to activation tasks can be derived through the use of a statistical model which accounts for both within-and between-session variance, combined with an appropriately large session sample size. If researchers have access to only a single session from a single subject, erroneous conclusions are a possibility, in that responses specific to this single session may be claimed to be typical responses for this subject.
tES-MEG: Simultaneous Combined Transcranial Electrical Stimulation and Magnetoencephalography
Brain Stimulation, 2015
Journal of Neuroscience, 2011
The neural mechanisms underlying variability in human sensory perception remain incompletely unde... more The neural mechanisms underlying variability in human sensory perception remain incompletely understood. In particular, few studies have attempted to investigate the relationship between in vivo measurements of neurochemistry and individuals' behavioral performance. Our previous work found a relationship between GABA concentration in the visual cortex and orientation discrimination thresholds ). In the present study, we used magnetic resonance spectroscopy of GABA and psychophysical testing of vibrotactile frequency thresholds to investigate whether individual differences in tactile frequency discrimination performance are correlated with GABA concentration in sensorimotor cortex. Behaviorally, individuals showed a wide range of discrimination thresholds ranging from 3 to 7.6 Hz around the 25 Hz standard. These frequency discrimination thresholds were significantly correlated with GABA concentration (r = −0.58; p < 0.05) in individuals' sensorimotor cortex, but not with GABA concentration in an occipital control region (r = −0.04). These results demonstrate a link between GABA concentration and frequency discrimination in vivo, and support the hypothesis that GABAergic mechanisms have an important role to play in sensory discrimination.
Psychological Medicine, 2010
Background. A wide range of neuropsychiatric conditions, including schizophrenia and autistic spe... more Background. A wide range of neuropsychiatric conditions, including schizophrenia and autistic spectrum disorder (ASD), are associated with impairments in social function. Previous studies have shown that individuals with schizophrenia and ASD have deficits in making a wide range of social judgements from faces, including decisions related to threat (such as judgements of approachability) and decisions not related to physical threat (such as judgements of intelligence). We have investigated healthy control participants to see whether there is a common neural system activated during such social decisions, on the basis that deficits in this system may contribute to the impairments seen in these disorders.
Between- and within-scanner variability in the CaliBrain study n-back cognitive task
Psychiatry Research: Neuroimaging, 2010
Psychiatric neuroimaging techniques are likely to improve understanding of the brain in health an... more Psychiatric neuroimaging techniques are likely to improve understanding of the brain in health and disease, but studies tend to be small, based in one imaging centre and of unclear generalisability. Multicentre studies have great appeal but face problems if functional magnetic resonance imaging (fMRI) data from different centres are to be combined. Fourteen healthy volunteers had two brain scans on different days at three scanners. Considerable effort was first made to use similar scanning sequences and standardise task implementation across centres. The n-back cognitive task was used to investigate between- and within-scanner reproducibility and reliability. Both the functional imaging and behavioural results were in good accord with the existing literature. We found no significant differences in the activation/deactivation maps between scanners, or between repeat visits to the same scanners. Between- and within-scanner reproducibility and reliability was very similar. However, the smoothness of images from the scanners differed, suggesting that smoothness equalization might further reduce inter-scanner variability. Our results for the n-back task suggest it is possible to acquire fMRI data from different scanners which allows pooling across centres, when the same field strength scanners are used and scanning sequences and paradigm implementations are standardised.
Loss of imagery phenomenology with intact visuo-spatial task performance: A case of ‘blind imagination’
Neuropsychologia, 2010
The capacity for imagery, enabling us to visualise absent items and events, is a ubiquitous featu... more The capacity for imagery, enabling us to visualise absent items and events, is a ubiquitous feature of our experience. This paper describes the case of a patient, MX, who abruptly lost the ability to generate visual images. He rated himself as experiencing almost no imagery on standard questionnaires, yet performed normally on standard tests of perception, visual imagery and visual memory. These unexpected findings were explored using functional MRI scanning (fMRI). Activation patterns while viewing famous faces were not significantly different between MX and controls, including expected activity in the fusiform gyrus. However, during attempted imagery, activation in MX&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s brain was significantly reduced in a network of posterior regions while activity in frontal regions was increased compared to controls. These findings are interpreted as suggesting that MX adopted a different cognitive strategy from controls when performing the imagery task. Evidence from experimental tasks thought to rely on mental imagery, such as the Brooks&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; matrices and mental rotation, support this interpretation. Taken together, these results indicate that successful performance in visual imagery and visual memory tasks can be dissociated from the phenomenal experience of visual imagery.
Functional Magnetic Resonance Imaging (fMRI) reproducibility and variance components across visits and scanning sites with a finger tapping task
NeuroImage, 2010
Multicentre MRI studies offer great potential to increase study power and flexibility, but it is ... more Multicentre MRI studies offer great potential to increase study power and flexibility, but it is not yet clear how reproducible the results from multiple centres may be. Here we present results from the multicentre study 'CaliBrain', examining the reproducibility of fMRI data within and between three sites. Fourteen subjects were scanned twice on three 1.5 T GE scanners using an identical scanning protocol. We present data from a motor task with three conditions, sequential and random finger tapping and rest. Similar activation maps were obtained for each site and visit; brain areas consistently activated during the task included the premotor, primary motor and supplementary motor areas, the striatum and cerebellum. Reproducibility was evaluated within and between sites by comparing the extent and spatial agreement of activation maps at both the subject and group levels. The results were within the range previously reported for similar tasks on single scanners and both mea...
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Papers by David McGonigle