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Biomedical subjects

A S David

Publications and source records attributed to A S David.

At least 37 records · Page 2Linked to original sources
PubMed2003

The health effects of peace-keeping in the UK Armed Forces: Bosnia 1992-1996. Predictors of psychological symptoms.

BACKGROUND: Peace-keeping duties are associated with unique stresses for military personnel. There have been few reports on the effects of peace-keeping on psychological health. METHOD: We used data from a cross-sectional study originally established to examine health effects of service in the Gulf War, which included a control group who had been deployed in Bosnia (N= 2049). This group was examined to establish which demographic, occupational, and deployment-related risk factors were associated with psychological distress measured on the General Health Questionnaire (GHQ-12) and stress symptoms akin to a post-traumatic stress reactions. RESULTS: The main risk factors for stress symptoms in the Bosnia group were--lower rank, being deployed early in the campaign, having more deployment-related exposures, and serving on staff duties. There was no protective effect of previous deployments to the Falklands or Northern Ireland, and time off following deployment was not protective. For GHQ-12 cases, the main risk factors were: female gender, lower rank, increased deployment-related exposures and serving on staff duties. CONCLUSIONS: This study suggests that stress symptoms and GHQ-12 cases, are strongly predicted both by experiences during deployment and demographic factors.

Adult↗
PubMed2002

The human amygdala: a systematic review and meta-analysis of volumetric magnetic resonance imaging.

The structure and function of the human amygdala is attracting increasing attention in the scientific literature, particularly since the advent of high resolution magnetic resonance imaging (MRI). We carried out a systematic review of the published literature reporting left and right amygdala volumes from MRI in non-clinical subjects. Our aim was to estimate the normal range of the volume of the amygdala and to account for heterogeneity of the measures. The factors we considered included the detail given regarding various subject factors, the plane of scan acquisition, slice thickness and contiguity, magnet strength, positional and volume correction, and the reliability of measurement. Thirty-nine studies with 51 data sets fulfilled selection criteria. The mean+/-95% confidence interval for the left amygdala volume was 1726.7 mm(3)+/-35.1, and right was 1691.7 mm(3)+/-37.2. The left-right difference did not reach statistical significance. The overall range of reported volumes was 1050 mm(3) to 3880 mm(3). The amygdala is significantly larger in men and shows an inverse correlation with age. The main methodological factor found to influence amygdala measurement was anatomical definition. Studies using 'Watson's criteria' (Neurology 42 (1992) 1743) produced significantly larger volumes than the remainder. An index of study quality revealed an inverse relationship with volume-the higher the quality the smaller the volume. This reflected such factors as slice thickness, correction for brain volume, positional correction and number of subjects. We conclude by putting forward a detailed operationalized anatomical delineation of the amygdala, based on Watson's criteria. This work should guide future research in obtaining accurate and reliable amygdala volume measures which in turn will aid comparisons with clinical groups and the specification of structural-functional relationships.

Amygdala↗
PubMed2002

Searching for a Gulf War syndrome using cluster analysis.

BACKGROUND: Gulf veterans report medically unexplained symptoms more frequently than non-Gulf veterans did. We examined whether Gulf and non-Gulf veterans could be distinguished by their patterns of symptom reporting. METHOD: A k-means cluster analysis was applied to 500 randomly sampled veterans from each of three United Kingdom military cohorts of veterans; those deployed to the Gulf conflict between 1990 and 1991; to the Bosnia peacekeeping mission between 1992 and 1997; and military personnel who were in active service but not deployed to the Gulf (Era). Sociodemographic, health variables and scores for ten symptom groups were calculated. RESULTS: The gap statistic indicated the five-group solution as one that provided a particularly informative description of the structure in the data. Cluster 1 consisted of low scores for all symptom groups. Cluster 2 had veterans with highest symptom scores for musculoskeletal symptoms and high scores for psychiatric symptoms. Cluster 3 had high scores for psychiatric symptoms and marginally elevated scores for the remaining nine groups symptom groups. Cluster 4 had elevated scores for musculoskeletal symptoms only and cluster 5 was distinguishable from the other clusters in having high scores in all symptom groups, especially psychiatric and musculoskeletal. CONCLUSION: The findings do not support the existence of a unique syndrome affecting a subgroup of Gulf veterans but emphasize the excess of non-specific self-reported ill health in this group.

Bosnia and Herzegovina↗
PubMed2002

Cognitive functioning and disturbances of mood in UK veterans of the Persian Gulf War: a comparative study.

BACKGROUND: Complaints of poor memory and concentration are common in veterans of the 1991 Persian Gulf War as are other symptoms. Despite a large research effort, such symptoms remain largely unexplained. METHOD: A comprehensive battery of neuropsychological tests and rating scales was administered to 341 UK servicemen who were returnees from the Gulf War and peace keeping duties in Bosnia, plus non-deployed military controls. All were drawn from a large randomized survey. Most were selected on the basis of impaired physical functioning defined operationally. RESULTS: Group comparisons revealed an association between physical functioning and symptoms of depression, post-traumatic stress reactions, increased anger and subjective cognitive failures. Poorer performance on some general cognitive measures, sequencing and attention was also seen in association with being 'ill' but virtually all differences disappeared after adjusting for depressed mood or multiple comparisons. Deployment was also associated with symptoms of post-traumatic stress and subjective cognitive failures, independently of health status, as well as minor general cognitive and constructional impairment. The latter remained significantly poorer in the Gulf group even after adjusting for depressed mood. CONCLUSIONS: Disturbances of mood are more prominent than quantifiable cognitive deficits in Gulf War veterans and probably lead to subjective underestimation of ability. Task performance deficits can themselves be explained by depressed mood although the direction of causality cannot be inferred confidently. Reduced constructional ability cannot be explained in this way and could be an effect of Gulf-specific exposures.

Adult↗
PubMed2002

Separating depersonalisation and derealisation: the relevance of the "lesion method".

OBJECTIVES: Depersonalisation (DP) and derealisation (DR) are often met with in patients with a wide range of localisable neurological conditions. This suggests that the "lesion method" might be a valid approach to study the neurobiology of DP/DR. However, the fact that anxiety can trigger DP/DR makes it difficult to establish whether the presence of DP/DR in neurological patients is mainly determined by coexisting anxiety or by lesion location. To overcome this difficulty, we suggest the study of neurological phenomena, which although not considered as DP/DR, bear enough phenomenological resemblance with them as to warrant their use as models. METHODS: One patient with "visual hypoemotionality" and another with "hemiasomatognosia" are described in detail together with a selective literature review. RESULTS: Complaints of patients with visual hypoemotionality are indistinguishable from those of patients with "visual derealisation". There is also a phenomenological overlap between "asomatognosia" and the symptom of "body alienation", which is a central feature of depersonalisation. CONCLUSIONS: Phenomenological similarities between visual hypoemotionality and DR suggest that a disruption of the process by means of which perception becomes emotionally coloured may be an underlying mechanism in both conditions. Likewise, phenomenological overlaps with asomatognosia suggest that DP might result from parietal mechanisms disrupting the experience of body ownership and agency. These findings give validity to the notion that DP and DR may have distinct neurobiological mechanisms.

Adult↗
PubMed2001

Depersonalization disorder: thinking without feeling.

Patients with depersonalization disorder (DP) experience a detachment from their own senses and surrounding events, as if they were outside observers. A particularly common symptom is emotional detachment from the surroundings. Using functional magnetic resonance imaging (fMRI), we compared neural responses to emotionally salient stimuli in DP patients, and in psychiatric and healthy control subjects. Six patients with DP, 10 with obsessive-compulsive disorder (OCD), and six volunteers were scanned whilst viewing standardized pictures of aversive and neutral scenes, matched for visual complexity. Pictures were then rated for emotional content. Both control groups rated aversive pictures as much more emotive, and demonstrated in response to these scenes significantly greater activation in regions important for disgust perception, the insula and occipito-temporal cortex, than DP patients (covarying for age, years of education and total extent of brain activation). In DP patients, aversive scenes activated the right ventral prefrontal cortex. The insula was activated only by neutral scenes in this group. Our findings indicate that a core phenomenon of depersonalization--absent subjective experience of emotion--is associated with reduced neural responses in emotion-sensitive regions, and increased responses in regions associated with emotion regulation.

Adult↗
PubMed2001

Basal activity of the hypothalamic-pituitary-adrenal axis in patients with depersonalization disorder.

Depersonalisation disorder may occur during severe anxiety or following a traumatic event, suggesting a possible role of stress hormones. This study investigated basal activity of the hypothalamic-pituitary-adrenal (HPA) axis in patients with depersonalisation disorder. Salivary cortisol levels were measured at four time points over 12 h in patients with depersonalisation disorder (N=13), major depressive disorder (MDD, N=14) and healthy controls (N=13). Beck Depression Inventory scores were significantly higher in depersonalised subjects than controls, while MDD subjects demonstrated higher scores than both groups. Basal cortisol levels of depersonalised subjects were significantly lower than those of MDD subjects but not healthy controls. These results point to reduced basal activity of the HPA axis in depersonalisation disorder. This pilot study supports the distinction between depersonalisation disorder and major depressive disorder which should be examined in a larger sample.

Adult↗
PubMed2001

Corpus callosum area and functioning in schizophrenic patients with auditory--verbal hallucinations.

Auditory--verbal hallucinations (AVH) are a characteristic feature of schizophrenia. Patients with AVHs have been found to differ from non-hallucinating patients in volumes of certain asymmetrical brain structures on MRI, and on certain neuropsychological measures. There is also evidence of corpus callosum (CC) abnormalities in schizophrenia, and it has been proposed that abnormalities of inter-hemispheric transmission may underlie hallucinations and other symptoms. The aim of this study was to examine whether patients with AVHs have smaller corpora callosa than those without AVH, and whether CC size is related to performance on neuropsychological tests of functional cerebral asymmetry. Seventy-one DSM-IV male schizophrenics were recruited on the basis of their hallucination history plus 33 matched normal controls. Twenty-nine patients had no history of AVH, and 42 had a strong history of AVH. The mid-sagittal surface area and longitudinal length of the CC were measured from T(1)-weighted spin echo images. Callosal area was divided into four sections. There were no significant differences in any of the measurements between the two patient groups, or between patients with schizophrenia and controls. There was no association between CC measures and handedness, or performance on dichotic listening or finger tapping tasks. The results of this study do not lend support for there being a major morphological abnormality of the corpus callosum in schizophrenic patients, or for a specific relationship to AVH. However, a significant association between CC area and overall grey and white matter volumes was noted in the hallucinating patients and, to a lesser extent, in the non-hallucinators, which may point to differing influences on brain development or degeneration in such patients compared with normal controls.

Adolescent↗
PubMed2001

Are auditory hallucinations the consequence of abnormal cerebral lateralization? A morphometric MRI study of the sylvian fissure and planum temporale.

BACKGROUND: Auditory verbal hallucinations (AVHs) are a characteristic feature of schizophrenia. Patients with schizophrenia have been found to have reduced volumes of a variety of brain structures as well as a reduction in right-left asymmetries, using postmortem and magnetic resonance imaging (MRI) measures. There is also evidence that patients with AVHs differ in these structural asymmetries, relative to those patients who do not hallucinate. The aim of this study was to examine whether patients with and without a prominent history of AVHs differ, both from each other and in comparison with normal subjects, in the asymmetry of the sylvian fissure (SF) and planum temporale (PT). METHODS: We recruited 74 DSM-IV male patients with schizophrenia (on the basis of their AVH history) and 32 matched normal control subjects. Thirty patients had no history of AVHs and 44 had a strong definitive history of AVHs. The SF length and PT area and volume were measured on a three-dimensional MRI spoiled GRASS volume sequence. Absolute measures and laterality coefficients were calculated. RESULTS: : All groups had the normal leftward asymmetry in both the SF and PT. Planum temporale volume and surface area and SF length were all larger in the left hemisphere. There were no significant differences in any measures between the two patient groups or between schizophrenic patients and control subjects. Greater leftward asymmetry of the SF correlated with hallucinations and thought disorder within the prominent hallucinator group. An association was found between handedness and brain size, but this did not interact with diagnosis. CONCLUSIONS: The results of this study do not confirm reports, based on smaller samples, of reduced structural asymmetries of either the SF or PT in schizophrenia, nor do they indicate a specific relationship to a propensity to experience AVHs. A modest correlation between leftward asymmetry of the SF and some positive symptomatology was found.

Adult↗
PubMed2001

Dispersed activation in the left temporal cortex for speech-reading in congenitally deaf people.

Does the lateral temporal cortex require acoustic exposure in order to become specialized for speech processing? Six hearing participants and six congenitally deaf participants, all with spoken English as their first langugage, were scanned using functional magnetic resonance imaging while performing a simple speech-reading task. Focal activation of the left lateral temporal cortex was significantly reduced in the deaf group compared with the hearing group. Activation within this region was present in individual deaf participants, but varied in location from person to person. Early acoustic experience may be required for regions within the left temporal cortex in order to develop into a coherent network with subareas devoted to specific speech analysis functions.

Adult↗
PubMed2001

Audio-visual speech perception in schizophrenia: an fMRI study.

Abnormalities in the integration of auditory and visual language inputs could underlie many core psychotic features. Perceptual confusion may arise because of the normal propensity of visual speech perception to evoke auditory percepts. Recent functional neuroimaging studies of normal subjects have demonstrated activation in auditory-linguistic brain areas in response to silent lip-reading. Three functional magnetic resonance imaging experiments were carried out on seven normal volunteers, and 14 schizophrenia patients, half of whom were actively psychotic. The tasks involved listening to auditory speech, silent lip-reading (visual speech), and perception of meaningless lip movements (visual non-speech). Subjects also undertook a behavioural study of audio-visual word identification designed to evoke perceptual fusions. Patients and controls both showed susceptibility to audio-visual fusions on the behavioural task. The patient group as a whole showed less activation relative to controls in superior and inferior posterior temporal areas while performing the silent lip-reading task. Attending to visual non-speech, the patients activated less posterior (occipito-temporal) and more anterior (frontal, insular and striatal) brain areas than controls. This difference was accounted for largely by the psychotic subgroup. Insular and striatal areas were also activated in both subject groups in the auditory speech perception condition, thus demonstrating the bimodal sensitivity of these regions. The results suggest that schizophrenia patients with psychotic symptoms respond to visually ambiguous stimuli (non-speech) by activation of polysensory structures. This could reflect particular processing strategies and may increase susceptibility to certain paranoid and hallucinatory symptoms.

Adult↗
PubMed2001

Arousal dissociates amygdala and hippocampal fear responses: evidence from simultaneous fMRI and skin conductance recording.

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.

Adult↗
PubMed2001

Recognizing one's own face.

We report two studies of facial self-perception using individually tailored, standardized facial photographs of a group of volunteers and their partners. A computerized morphing procedure was used to merge each target face with an unknown control face. In the first set of experiments, a discrimination task revealed a delayed response time for the more extensively morphed self-face stimuli. In a second set of experiments, functional magnetic resonance imaging (fMRI) was used to measure brain activation while subjects viewed morphed versions of either their own or their partner's face, alternating in blocks with presentation of an unknown face. When subjects viewed themselves (minus activation for viewing an unknown face), increased blood oxygenation was detected in right limbic (hippocampal formation, insula, anterior cingulate), left prefrontal cortex and superior temporal cortex. In the partner (versus unknown) experiment, only the right insula was activated. We suggest that a neural network involving the right hemisphere in conjunction with left-sided associative and executive regions underlies the process of visual self-recognition. Together, this combination produces the unique experience of self-awareness.

Adult↗
PubMed2001

Brain activation during automatic and controlled processing of semantic relations: a priming experiment using lexical-decision.

Semantic relations may be studied using the experimental technique known as semantic priming, in which a word 'primes' the processing of a related target (e.g. lion-tiger), following a short delay. Priming may be automatic or, with longer delays, under more controlled processing. This study used functional magnetic resonance imaging (fMRI) to examine the cerebral activation during two lexical-decision semantic priming experiments, with a short and long delay, representing automatic and controlled processing, respectively. A further two un-primed lexical-decision tasks were performed to distinguish cerebral activation specific to semantic priming itself from those utilised during lexical-decision processes. Distinct regions of anterior cingulate cortex (ACC) were critical to automatic and controlled semantic priming, whilst the putamen and hippocampal complex responded differently to unrelated and semantically related prime-target pairs. Lexical-decision alone revealed activation in posterior temporal cortex especially on the left, in agreement with previous neuroimaging studies. The results provide a plausible neural substrate for common semantic relations independent of task demands and further emphasise the regional functional specialisation of the ACC.

Adult↗
PubMed2001

Primary and secondary depersonalisation disorder: a psychometric study.

INTRODUCTION: Depersonalisation may be part of a symptom-complex, a primary or a secondary disorder. Optimal methods of measurement and diagnosis have not been established. METHODS: We assessed 42 patients with primary or secondary depersonalisation, plus psychiatric and non-psychiatric controls using a variety of self-report questionnaire scales including the Beck depression and anxiety Inventories, and one developed by the authors (the Fewtrell Depersonalisation Scale (FDS)). The correlations between the scales and measures of anxiety and depression were calculated, as were sensitivity and specificity against an operational case definition. RESULTS: All the scales were highly correlated. All could distinguish depersonalisation cases from the rest but none could distinguish between primary and secondary depersonalisation disorder. Anxiety and especially depression were correlated with depersonalisation symptoms. The FDS had high sensitivity (85.7%) and specificity (92.3%) which compared favourably with other instruments. Patients with both derealisation and depersonalisation scored the highest on the FDS. DISCUSSION: Depersonalisation disorder comprises a measurable cluster of symptoms which may be quantified with the help of self-report scales. Primary and secondary forms overlap, with depressed mood a frequent feature.

Adolescent↗
PubMed2001

Cortical substrates for the perception of face actions: an fMRI study of the specificity of activation for seen speech and for meaningless lower-face acts (gurning).

Can the cortical substrates for the perception of face actions be distinguished when the superficial visual qualities of these actions are very similar? Two fMRI experiments are reported. Compared with watching the face at rest, observing silent speech was associated with bilateral activation in a number of temporal cortical regions, including the superior temporal sulcus (STS). Watching face movements of similar extent and duration, but which could not be construed as speech (gurning; Experiment 1b) was not associated with activation of superior temporal cortex to the same extent, especially in the left hemisphere. Instead, the peak focus of the largest cluster of activation was in the posterior part of the inferior temporal gyrus (right, BA 37). Observing silent speech, but not gurning faces, was also associated with bilateral activation of inferior frontal cortex (BA 44 and 45). In a second study, speechreading and observing gurning faces were compared within a single experiment, using stimuli which comprised the speaker's face and torso (and hence a much smaller image of the speaker's face and facial actions). There was again differential engagement of superior temporal cortex which followed the pattern of Experiment 1. These findings suggest that superior temporal gyrus and neighbouring regions are activated bilaterally when subjects view face actions--at different scales--that can be interpreted as speech. This circuitry is not accessed to the same extent by visually similar, but linguistically meaningless actions. However, some temporal regions, such as the posterior part of the right superior temporal sulcus, appear to be common processing sites for processing both seen speech and gurns.

Adult↗