Anthony S. David

YNICL Journal 2024 Journal Article

Response to the Letter Concerning the Publication: Neuroimaging in Functional Neurological Disorder: State of the Field and Research Agenda. Perez DL et al. Neuroimage Clin. 2021;30:102623

• David L. Perez
• Timothy R. Nicholson
• Ali A. Asadi-Pooya
• Matthew Butler
• Alan J. Carson
• Anthony S. David
• Quinton Deeley
• Ibai Diez

In their letter, Tuller and colleagues raise concerns regarding the following introductory phrase and the linked Stone et al (2010) reference: "this renewed interest parallels recognition that FND [functional neurological disorder] is the 2nd most common outpatient neurologic diagnosis."While we appreciate there is complexity to epidemiological considerations in FND, we do not agree with the concerns raised.We share our perspective on this matter with the following four points:

YNICL Journal 2021 Journal Article

Neuroimaging in Functional Neurological Disorder: State of the Field and Research Agenda

• David L. Perez
• Timothy R. Nicholson
• Ali A. Asadi-Pooya
• Indrit Bègue
• Matthew Butler
• Alan J. Carson
• Anthony S. David
• Quinton Deeley

Functional neurological disorder (FND) was of great interest to early clinical neuroscience leaders. During the 20th century, neurology and psychiatry grew apart - leaving FND a borderland condition. Fortunately, a renaissance has occurred in the last two decades, fostered by increased recognition that FND is prevalent and diagnosed using "rule-in" examination signs. The parallel use of scientific tools to bridge brain structure - function relationships has helped refine an integrated biopsychosocial framework through which to conceptualize FND. In particular, a growing number of quality neuroimaging studies using a variety of methodologies have shed light on the emerging pathophysiology of FND. This renewed scientific interest has occurred in parallel with enhanced interdisciplinary collaborations, as illustrated by new care models combining psychological and physical therapies and the creation of a new multidisciplinary FND society supporting knowledge dissemination in the field. Within this context, this article summarizes the output of the first International FND Neuroimaging Workgroup meeting, held virtually, on June 17th, 2020 to appraise the state of neuroimaging research in the field and to catalyze large-scale collaborations. We first briefly summarize neural circuit models of FND, and then detail the research approaches used to date in FND within core content areas: cohort characterization; control group considerations; task-based functional neuroimaging; resting-state networks; structural neuroimaging; biomarkers of symptom severity and risk of illness; and predictors of treatment response and prognosis. Lastly, we outline a neuroimaging-focused research agenda to elucidate the pathophysiology of FND and aid the development of novel biologically and psychologically-informed treatments.

YNICL Journal 2016 Journal Article

Volumetric, relaxometric and diffusometric correlates of psychotic experiences in a non-clinical sample of young adults

• Mark Drakesmith
• Anirban Dutt
• Leon Fonville
• Stanley Zammit
• Abraham Reichenberg
• C. John Evans
• Philip McGuire
• Glyn Lewis

BACKGROUND: Grey matter (GM) abnormalities are robust features of schizophrenia and of people at ultra high-risk for psychosis. However the extent to which neuroanatomical alterations are evident in non-clinical subjects with isolated psychotic experiences is less clear. METHODS: Individuals (mean age 20 years) with (n = 123) or without (n = 125) psychotic experiences (PEs) were identified from a population-based cohort. All underwent T1-weighted structural, diffusion and quantitative T1 relaxometry MRI, to characterise GM macrostructure, microstructure and myelination respectively. Differences in quantitative GM structure were assessed using voxel-based morphometry (VBM). Binary and ordinal models of PEs were tested. Correlations between socioeconomic and other risk factors for psychosis with cortical GM measures were also computed. RESULTS: GM volume in the left supra-marginal gyrus was reduced in individuals with PEs relative to those with no PEs. The greater the severity of PEs, the greater the reduction in T1 relaxation rate (R1) across left temporoparietal and right pre-frontal cortices. In these regions, R1 was positively correlated with maternal education and inversely correlated with general psychopathology. CONCLUSIONS: PEs in non-clinical subjects were associated with regional reductions in grey-matter volume reduction and T1 relaxation rate. The alterations in T1 relaxation rate were also linked to the level of general psychopathology. Follow up of these subjects should clarify whether these alterations predict the later development of an ultra high-risk state or a psychotic disorder.

YNIMG Journal 2014 Journal Article

Self-regulation of the anterior insula: Reinforcement learning using real-time fMRI neurofeedback

• Emma J. Lawrence
• Li Su
• Gareth J. Barker
• Nick Medford
• Jeffrey Dalton
• Steve C.R. Williams
• Niels Birbaumer
• Ralf Veit

The anterior insula (AI) plays a key role in affective processing, and insular dysfunction has been noted in several clinical conditions. Real-time functional MRI neurofeedback (rtfMRI-NF) provides a means of helping people learn to self-regulate activation in this brain region. Using the Blood Oxygenated Level Dependant (BOLD) signal from the right AI (RAI) as neurofeedback, we trained participants to increase RAI activation. In contrast, another group of participants was shown ‘control’ feedback from another brain area. Pre- and post-training affective probes were shown, with subjective ratings and skin conductance response (SCR) measured. We also investigated a reward-related reinforcement learning model of rtfMRI-NF. In contrast to the controls, we hypothesised a positive linear increase in RAI activation in participants shown feedback from this region, alongside increases in valence ratings and SCR to affective probes. Hypothesis-driven analyses showed a significant interaction between the RAI/control neurofeedback groups and the effect of self-regulation. Whole-brain analyses revealed a significant linear increase in RAI activation across four training runs in the group who received feedback from RAI. Increased activation was also observed in the caudate body and thalamus, likely representing feedback-related learning. No positive linear trend was observed in the RAI in the group receiving control feedback, suggesting that these data are not a general effect of cognitive strategy or control feedback. The control group did, however, show diffuse activation across the putamen, caudate and posterior insula which may indicate the representation of false feedback. No significant training-related behavioural differences were observed for valence ratings, or SCR. In addition, correlational analyses based on a reinforcement learning model showed that the dorsal anterior cingulate cortex underpinned learning in both groups. In summary, these data demonstrate that it is possible to regulate the RAI using rtfMRI-NF within one scanning session, and that such reward-related learning is mediated by the dorsal anterior cingulate.

YNIMG Journal 2010 Journal Article

Neural response to specific components of fearful faces in healthy and schizophrenic adults

• Joaquim Radua
• Mary L. Phillips
• Tamara Russell
• Natalia Lawrence
• Nicolette Marshall
• Sridevi Kalidindi
• Wissam El-Hage
• Colm McDonald

Perception of fearful faces is associated with functional activation of cortico-limbic structures, which has been found altered in individuals with psychiatric disorders such as schizophrenia, autism and major depression. The objective of this study was to isolate the brain response to the features of standardized fearful faces by incorporating principal component analysis (PCA) into the analysis of neuroimaging data of healthy volunteers and individuals with schizophrenia. At the first stage, the visual characteristics of morphed fearful facial expressions (FEEST, Young et al. , 2002) were classified with PCA, which produced seven orthogonal factors, with some of them related to emotionally salient facial features (eyes, mouth, brows) and others reflecting non-salient facial features. Subsequently, these PCA-based factors were included into the functional magnetic resonance imaging (fMRI) analysis of 63 healthy volunteers and 32 individuals with schizophrenia performing a task that involved implicit processing of FEEST stimuli. In healthy volunteers, significant neural response was found to visual characteristics of eyes, mouth or brows. In individuals with schizophrenia, PCA-based analysis enabled us to identify several significant clusters of activation that were not detected by the standard approach. These clusters were implicated in processing of visual and emotional information and were attributable to the perception of eyes and brows. PCA-based analysis could be useful in isolating brain response to salient facial features in psychiatric populations.

YNIMG Journal 2009 Journal Article

A parametric approach to voxel-based meta-analysis

• Sergi G. Costafreda
• Anthony S. David
• Michael J. Brammer

A key aim of meta-analysis in functional neuroimaging is to quantify the consistency of regional cerebral responses across studies. We derive here a parametric approach to voxel-based meta-analysis, based on spatial statistics. In this method, the value of each voxel in the meta-analysis summary map reflects the proportion of studies reporting an activation within a specified local neighborhood. We threshold this map by testing whether voxel scores could have been expected had the activation peaks been generated at random locations. Our aim is to detect ‘signal’ regions, with scores that are unlikely to arise under such null hypothesis. The method is applicable to both fixed-effects (in which each study is considered as deriving from the same generating process) and random-effects (in which the process varies across studies) meta-analysis. Simulations show strict false positive control, and this approach leads to increased power and substantial gains in computational time relative to existing simulation-based alternatives. We illustrate the technique by performing a random-effects meta-analysis of word production. Parametric voxel-based meta-analysis provides a powerful and practical tool for neuroimaging meta-analysis.

YNIMG Journal 2008 Journal Article

Corrigendum to “Fingerspelling, signed language, text and picture processing in deaf native signers: The role of the mid-fusiform gyrus” [NeuroImage 35 (2007) 1287–1302]

• Dafydd Waters
• Ruth Campbell
• Cheryl M. Capek
• Bencie Woll
• Anthony S. David
• Philip K. McGuire
• Michael J. Brammer
• Mairéad MacSweeney

We recently noticed an error in the Methods section of this paper. Voxel size in Talairach space was reported as 3×3×3 mm. It was actually 3.3×3.3×3.3 mm. Due to this error, and to a systematic error in calculating metric volume, activation volumes were reported incorrectly throughout the paper. These errors have no impact, however, on the arguments presented. In the Results section, and in Tables 3–8, activation sizes are given as both number of activated voxels and metric volume. In all cases, the figure reported for the number of voxels is correct, whereas the volume reported is incorrect. The following formula may be used to calculate the correct volume for these activations:

IROS Conference 2008 Conference Paper

Sequential Method of Analytical Potentials an approach for the biped robots dynamic gait generation

• Anthony S. David
• Olivier Bruneau

This paper presents a tool called sequential method of analytical potentials aiming to generate dynamic gaits for biped robots. The objective is to control the different accelerations governing the evolution of the robot by modifying precisely and directly its own dynamic effects. Taking into account the intrinsic dynamics of the robot as well as the capability of its joint actuators, this method is based on the use of the dynamic propulsion potential and is illustrated on the biped robot RABBIT.

YNIMG Journal 2007 Journal Article

Fingerspelling, signed language, text and picture processing in deaf native signers: The role of the mid-fusiform gyrus

• Dafydd Waters
• Ruth Campbell
• Cheryl M. Capek
• Bencie Woll
• Anthony S. David
• Philip K. McGuire
• Michael J. Brammer
• Mairéad MacSweeney

In fingerspelling, different hand configurations are used to represent the different letters of the alphabet. Signers use this method of representing written language to fill lexical gaps in a signed language. Using fMRI, we compared cortical networks supporting the perception of fingerspelled, signed, written, and pictorial stimuli in deaf native signers of British Sign Language (BSL). In order to examine the effects of linguistic knowledge, hearing participants who knew neither fingerspelling nor a signed language were also tested. All input forms activated a left fronto-temporal network, including portions of left inferior temporal and mid-fusiform gyri, in both groups. To examine the extent to which activation in this region was influenced by orthographic structure, two contrasts of orthographic and non-orthographic stimuli were made: one using static stimuli (text vs. pictures), the other using dynamic stimuli (fingerspelling vs. signed language). Greater activation in left and right inferior temporal and mid-fusiform gyri was found for pictures than text in both deaf and hearing groups. In the fingerspelling vs. signed language contrast, a significant interaction indicated locations within the left and right mid-fusiform gyri. This showed greater activation for fingerspelling than signed language in deaf but not hearing participants. These results are discussed in light of recent proposals that the mid-fusiform gyrus may act as an integration region, mediating between visual input and higher-order stimulus properties.

IROS Conference 2006 Conference Paper

Analytical Approach for the Generation of Highly Dynamic Gaits for Walking Robots

• Olivier Bruneau
• Anthony S. David

This paper presents an analytical approach for the generation of walking gaits with a high dynamic behaviour. The principle is to modify the dynamic effects generated by the robot directly by taking into account the intrinsic dynamics of the robot as well as the capability of its joint torques. In order to perform this, two criterions based on dynamics are proposed: the "dynamic propulsion criterion" and the "dynamic propulsion potential". This general approach is illustrated for an underactuated robot without foot, which can not be statically stable

IROS Conference 2006 Conference Paper

Dynamic Stabilization of an Under-Actuated Robot using Dynamic Effects of the Legs and the Trunk

• Anthony S. David
• Olivier Bruneau

This paper presents the first theoretical tools to control an under-actuated robot by taking into account its intrinsic dynamics. In order to perform this control, the idea is to modify the configuration and the dynamic effects of the robot if the measured velocity of the robot is not the desired one

YNIMG Journal 2006 Journal Article

How metaphors influence semantic relatedness judgments: The role of the right frontal cortex

• Argyris K. Stringaris
• Nicholas Medford
• Rachel Giora
• Vincent C. Giampietro
• Michael J. Brammer
• Anthony S. David

We used event-related fMRI (ER-fMRI) to test the hypothesis that metaphors bias cognitive processing of semantic relatedness towards a search for a wider range of associations. Twelve right-handed male volunteers read a mixture of metaphoric and literal sentences, each sentence being followed by a single word, which could be semantically related or not to the preceding sentence context. We found that judging unrelated words as contextually irrelevant was associated with increased blood oxygenation level-dependent (BOLD) signal in the right ventrolateral prefrontal cortex in the metaphoric but not in the literal condition. The same region was also activated when subjects endorsed a semantic relation between words and metaphoric sentence primes but not between words and literal sentence primes. We argue that these results are consistent with the notion of semantic open-endedness, whereby figurative statements bias cognitive processing towards a search for a wider range of semantic relationships compared to literal statements, and thus lend further support to the view that coarse semantic coding occurs preferentially in the right hemisphere.

YNIMG Journal 2006 Journal Article

Time-resolved fMRI of mental rotation revisited-dissociating visual perception from mental rotation in female subjects

• Christine Ecker
• Michael J. Brammer
• Anthony S. David
• Steven C. Williams

Functional neuroimaging studies have demonstrated that mental rotation paradigms activate a network of spatially distributed cortical areas rather than a discrete brain region. Although the neuro-anatomical nodes of the rotation network are well established, their specific functional role is less well identified. It was the aim of the present study to dissociate network components involved in the visual perception of 3D cubic objects from regions involved in their mental spatial transformation. This was achieved by desynchronizing the time course of the perceptional process (i. e. , stimulus duration) from the duration of the cognitive process (i. e. , reaction times) and by comparing these with the temporal characteristics of the hemodynamic response functions (HRFs) in regions of interest. To minimize intersubject variability, an all-female subject group was chosen for this investigation. Time-resolved fMRI analysis revealed a significant increase in the full width at half maximum (FWHM) of the HRF with reaction times in the supplementary motor area (pre-SMA), in the bilateral premotor cortex (PMd-proper), and in the left parietal lobe (PP). The FWHM in visual system components such as the bilateral lateral occipital complex (LOC) and dorsal extrastriate visual areas (DE) was constant across trials and roughly equal to the stimulus duration. These findings suggest that visual system activation during mental rotation reflects visual perception and can be dissociated from other network components whose response characteristics indicates an involvement in the mental spatial transformation itself.

YNIMG Journal 2001 Journal Article

Arousal Dissociates Amygdala and Hippocampal Fear Responses: Evidence from Simultaneous fMRI and Skin Conductance Recording

• Leanne M. Williams
• Mary L. Phillips
• Michael J. Brammer
• David Skerrett
• Jim Lagopoulos
• Chris Rennie
• Homayoun Bahramali
• Gloria Olivieri

The experience and appraisal of threat is essential to human and animal survival. Lesion evidence suggests that the subjective experience of fear relies upon amygdala-medial frontal activity (as well as autonomic arousal), whereas the factual context of threat stimuli depends upon hippocampal-lateral frontal activity. This amygdala-hippocampus dissociation has not previously been demonstrated in vivo. To explore this differentiation, we employed functional magnetic resonance imaging (fMRI) and simultaneous skin conductance response (SCR) measures of phasic arousal, while subjects viewed fearful versus neutral faces. fMRI activity was subaveraged according to whether or not the subject evoked an arousal SCR to each discrete face stimulus. The fMRI-with arousal and fMRI-without arousal data provided a distinct differentiation of amygdala and hippocampal networks. Amygdala-medial frontal activity was observed only with SCRs, whereas hippocampus-lateral frontal activity occurred only in the absence of SCRs. The findings provide direct evidence for a dissociation between human amygdala and hippocampus networks in the visceral experience versus declarative fact processing of fear.

YNIMG Journal 1998 Journal Article

Measures of functional and structural cerebral asymmetries: relationship to auditory-verbal hallucinations

• Susan L. Rossell
• Jane Shapleske
• Peter W.R. Woodruff
• Andrew Simmons
• Anthony S. David