Biomedical subjects

Anthony S David

Publications and source records attributed to Anthony S David.

65 records · Page 4Linked to original sources

PubMed2002

Cross-modal semantic priming in schizophrenia.

Work on implicit memory in normal subjects has demonstrated the influence of stimulus modality on the retrieval of semantic information. The present study examined the effects of auditory and visual semantic priming on the recognition of visual words using a lexical decision task. Performance was studied in a group of 20 patients with DSM-IV schizophrenia and 26 normal volunteers of similar age and sex. There were two versions of the task: ipsimodal, in which the word or nonword visual target followed 400 ms after the onset of a visual word prime which may or may not be semantically related to the target; and cross-modal, in which the visual target followed 400 ms after the onset of an auditory word prime. Both groups showed significant priming in both modality conditions, although the schizophrenia patients exhibited significantly greater priming in the cross-modal condition. Priming effects in the ipsimodal condition did not differ substantially between patients and controls. The priming effects in the two conditions correlated with each other in the schizophrenia patients only. The results suggest that priming may occur through amodal semantic representations. In schizophrenia, there appears to be increased cross-modal connectivity (reduced modality modularity and informational encapsulation) between lexical representations that could result in impaired language, particularly speech, processing.

Adult↗

PubMed2002

Neural systems underlying British Sign Language and audio-visual English processing in native users.

In order to understand the evolution of human language, it is necessary to explore the neural systems that support language processing in its many forms. In particular, it is informative to separate those mechanisms that may have evolved for sensory processing (hearing) from those that have evolved to represent events and actions symbolically (language). To what extent are the brain systems that support language processing shaped by auditory experience and to what extent by exposure to language, which may not necessarily be acoustically structured? In this first neuroimaging study of the perception of British Sign Language (BSL), we explored these questions by measuring brain activation using functional MRI in nine hearing and nine congenitally deaf native users of BSL while they performed a BSL sentence-acceptability task. Eight hearing, non-signing subjects performed an analogous task that involved audio-visual English sentences. The data support the argument that there are both modality-independent and modality-dependent language localization patterns in native users. In relation to modality-independent patterns, regions activated by both BSL in deaf signers and by spoken English in hearing non-signers included inferior prefrontal regions bilaterally (including Broca's area) and superior temporal regions bilaterally (including Wernicke's area). Lateralization patterns were similar for the two languages. There was no evidence of enhanced right-hemisphere recruitment for BSL processing in comparison with audio-visual English. In relation to modality-specific patterns, audio-visual speech in hearing subjects generated greater activation in the primary and secondary auditory cortices than BSL in deaf signers, whereas BSL generated enhanced activation in the posterior occipito-temporal regions (V5), reflecting the greater movement component of BSL. The influence of hearing status on the recruitment of sign language processing systems was explored by comparing deaf and hearing adults who had BSL as their first language (native signers). Deaf native signers demonstrated greater activation in the left superior temporal gyrus in response to BSL than hearing native signers. This important finding suggests that left- temporal auditory regions may be privileged for processing heard speech even in hearing native signers. However, in the absence of auditory input this region can be recruited for visual processing.

Adolescent↗

PubMed2002

A computational morphometric MRI study of schizophrenia: effects of hallucinations.

Quantitative magnetic resonance imaging (MRI) studies in patients with schizophrenia have shown reliable deficits in global tissue volume as well as some regionally specific changes, particularly in the temporal and frontal lobes. Recent technical advances have enabled automated voxel-wise analyses, which have the advantage of facilitating whole brain coverage without the restrictions of anatomically defined regions of interest and imperfect rater reliability. We used such a method to estimate voxel composition from segmentation of bivariate, dual-echo spin-echo data in 72 men with schizophrenia. Of these, 41 had a prominent history of auditory-verbal hallucinations and 31 had no such history. The patients were compared with 32 age, gender, handedness and IQ matched healthy controls. The study revealed localized areas of reduced grey-matter tissue proportion aggregating around the medial temporal lobes, the insulae, orbito-frontal cortex including anterior cingulate, and the precuneus (and lingual) gyri, in the schizophrenia patients as a whole. There were also reductions in white-matter tissue proportion extending along much of the large anterior-posterior frontal tracts in the right hemisphere. Small regions of increased grey matter were also noted in the right inferior parietal lobe. A contrast between the hallucinator and non-hallucinator patient groups showed a single region of reduced grey-matter tissue proportion affecting the left insula and adjacent temporal lobe. These data confirm the utility of voxel-based morphometric methods in schizophrenia research and point towards disruption to a 'paralimbic' neural network, as underlying schizophrenic psychopathology in general, with abnormalities of the left insula specifically related to hallucinations.

Adult↗

PubMed2002

The spectrum of organic depersonalization: a review plus four new cases.

Depersonalization and derealization are commonly reported in the general population as a response to stress. The symptoms have also been described in patients with a primary psychiatric or organic diagnosis, where their secondary status precludes a DSM-IV diagnosis of depersonalization disorder. The authors present 4 new cases of depersonalization in patients with an underlying organic condition, along with 47 cases from the literature in which the available information permits diagnosis of organic depersonalization. Information from case series documenting depersonalization in the context of medical illnesses is also presented and the underlying etiology discussed. Epilepsy and migraine appear to be the disorders most commonly associated with depersonalization. Left-sided temporal lobe dysfunction and anxiety are suggested as factors in the development of depersonalization; however, further studies are needed to determine the relationship. The introduction to the DSM-IV of an organic subtype of depersonalization disorder would facilitate research in this area.

Adolescent↗

PubMed2002

The perception of emotional chimeric faces in schizophrenia: further evidence of right hemisphere dysfunction.

OBJECTIVE: To examine lateral perceptual bias, an index of right hemisphere function, and its relation to performance on a standard facial perception test and to clinical variables in a large sample of first episode and chronic schizophrenia. BACKGROUND: Judgments made on chimeric faces reliably elicit a perceptual bias to the left hemispace, presumed to be a result of right hemisphere dominance for spatial attention. Recent studies have suggested that this bias is reduced or absent in people with schizophrenia. METHODS: Fifty first-episode and 50 patients with chronic schizophrenic and 50 control subjects were given a brief neuropsychologic battery that included a Happy-Sad Chimeric Face test and the Benton Facial Recognition Test. All patients were rated on the Positive and Negative Syndrome Scale of Schizophrenia after 4 weeks of neuroleptic treatment. All were right handed RESULTS: The patients with schizophrenia showed a significantly weaker perceptual left hemispatial bias compared with controls. In fact the mean bias was in the opposite direction in the chronic group. There was no correlation between left hemispatial bias and either positive or negative symptoms, current medication dose, or mood. Results from the Benton test revealed a performance deficit among the patients with schizophrenia compared with controls but was not correlated with performance on the chimeric faces test in the patients. CONCLUSIONS: The results confirm a specific deficit in right hemisphere attentional functions in schizophrenia, which is separate from a general impairment in facial processing. The deficit is most marked in chronic patients but further study is required to determine whether this is a consequence of prolonged illness.

Adult↗

PubMed2002

Self-reported health of Persian Gulf War veterans: a comparison of help-seeking and randomly ascertained cases.

The objective of this study was to compare self-selected Persian Gulf War veterans attending a health assessment program with veterans ascertained in an epidemiological study to determine why Gulf War veterans do, or do not, present for clinical assessment. A postal survey was sent to randomly selected United Kingdom Armed Forces personnel who served in the Persian Gulf conflict. Outcome measures included a symptom checklist, health perception, physical functioning, psychological distress, post-traumatic stress symptoms, and health attributions. A total of 173 survey respondents had also attended the Medical Assessment Program (MAP). MAP attendees were more likely to be female, older, and working part time or not working at all. They had poorer health perception and reported higher levels of illness, and they differed in terms of their health attributions. The belief that one had Gulf War syndrome and attributing health problems to Gulf War service were the most powerful predictors of MAP attendance, even when controlling for the level of physical functioning. The findings suggest that health beliefs rather than symptoms are more important predictors of attendance of an assessment program and that Gulf War veterans who attended the MAP have different characteristics than those who did not. This suggests that MAP patients are unrepresentative of the wider deployment to the Persian Gulf.

Adult↗

PubMed2000

The relationship between cognitive inhibition and psychotic symptoms.

Cognitive models of schizophrenia have highlighted deficits of inhibitory attentional processes as central to the disorder. This has been investigated using "negative priming" (S. P. Tipper, 1985), with schizophrenia patients showing a reduction of negative priming in a number of studies. This study attempted to replicate these findings, but studied psychotic symptoms rather than the broad diagnostic category of schizophrenia. Psychotic individuals exhibiting positive symptoms were compared with asymptomatic psychiatric patients and with a normal control group. As predicted, the symptomatic group failed to show the usual negative priming effect, which was present in the asymptomatic and normal groups. A modest but significant correlation was found between negative priming and delusions. Neither diagnosis, nor affective or negative symptoms, nor chronicity, nor medication, was related to negative priming. These data replicate previous findings that positive symptoms are related to a reduction in cognitive inhibition, although considerable variability was observed among the psychotic patients.

Adult↗

PubMedDate not supplied

Prevalence of mental incapacity in medical inpatients and associated risk factors: cross-sectional study.

BACKGROUND: Although mental incapacity is becoming increasingly important in clinical practice, little information is available on its frequency in medical inpatients. We aimed to estimate the prevalence of mental incapacity in acutely admitted medical inpatients; to determine the frequency that medical teams recognised patients who did not have mental capacity; and to identify factors associated with mental incapacity. METHODS: Over an 18-month period, we recruited 302 consecutive acute medical inpatients. Participants were assessed with the MacArthur competence tool for treatment and by clinical interview. Cognitive impairment was measured by the mini-mental state examination. FINDINGS: 72 (24%) patients were severely cognitively impaired, unconscious, or unable to express a choice and were automatically assigned to the incapacity group. 71 (24%) refused to participate or could not speak English. Thus, 159 patients were interviewed. Of these, 31% (95% CI 24-38) were judged not to have mental capacity. For the total sample (n=302), we estimated that at least 40% did not have mental capacity. Clinical teams rarely identified patients who did not have mental capacity: of 50 patients interviewed, 12 (24%) were rated as lacking capacity. Factors associated with mental incapacity were increasing age and cognitive impairment. INTERPRETATION: Mental incapacity is common in acutely ill medical inpatients, and clinicians tend not to recognise it. Screening methods for cognitive impairment could be useful in detecting those with doubtful capacity to consent.

Acute Disease↗

PubMedDate not supplied

Delusion formation and insight in the context of affective disturbance.

OBJECTIVE: Delusions and lack of insight have traditionally been viewed as the defining characteristics of insanity and in modern psychiatry continue to be central to the diagnosis of psychosis. Little is known about the mechanisms of delusion formation and much of the research into delusions and lack of insight has been focussed on schizophrenia, in spite of the fact that these symptoms are also prominent in other disorders e.g., affective psychosis. The objective of this paper is to review the literature on existing theories of delusions and insight with reference to the effects of affective disturbance on memory processes. METHOD: Narrative review supplemented by literature searches using Medline, PsycINFO and EMBASE databases for the period 1980 to present using terms "delusion", and "insight" and "affect". RESULTS: The role of affect on memory in normal psychology and delusions in psychopathology is being increasingly recognised. We sketch out a theory which gives weight to locating the formation and maintenance of mood congruent and mood incongruent delusional beliefs (and insight into such beliefs) within a model of normal memory processes. CONCLUSION: We conclude that delusional beliefs may represent false or biased memories of internal or external events modified and strengthened of by affective states. We propose that insight rests on an ability to identify these memories as internally generated or biased. In view of the growing body of knowledge accumulating from the study of memory, emotion and their neuropsychological correlates we would suggest using this as an evidence base for the further neuropsychiatric investigation of delusional beliefs.

Delusions↗

PubMedDate not supplied

The cognitive neuropsychiatry of auditory verbal hallucinations: an overview.

INTRODUCTION: The cognitive neuropsychiatric approach to auditory verbal hallucinations (AVHs) attempts to explain the phenomena in cognitive or information-processing terms and ultimately their brain bases. METHODS: A narrative review of the literature and an overview of this special issue of Cognitive Neuropsychiatry. RESULTS: First, an operational definition of AVHs is offered. Next, clues to etiology are derived from a detailed consideration of the clinical phenomenology of "voices", their form and content. Functional and structural neuroimaging studies suggest the importance of left-side language areas in the generation/perception of AVHs. CONCLUSIONS: Existing cognitive neuropsychiatric models provide a useful framework for the understanding of AVHs. However, data need to be applied more specifically to these models so that they may be refined.

Journal Article↗

PubMedDate not supplied

Lamotrigine as an add-on treatment for depersonalization disorder: a retrospective study of 32 cases.

OBJECTIVES: Depersonalization disorder (DPD) is a chronic condition characterized by the persistent subjective experience of unreality and detachment from the self. To date, there is no known treatment. Lamotrigine as sole agent was not found to be effective in a previous small double-blind, randomized crossover trial. However, evidence from open trials suggests that it may be beneficial as an add-on medication with antidepressants. METHODS: We report here an extended series of 32 patients with DPD in whom lamotrigine was prescribed as an augmenting medication. Most of the patients were receiving selective serotonin reuptake inhibitors. RESULTS: Fifty-six percent (n = 18) of patients had a more than or equal to 30% reduction on the Cambridge Depersonalization Scale score at follow-up. Both maximum dose of lamotrigine used and before treatment Cambridge Depersonalization Scale scores showed positive correlations with the percentage of response. CONCLUSIONS: The results of this trial suggest that a significant number of patients with DPD may respond to lamotrigine when combined with antidepressant medication. The results are sufficiently positive to prompt a larger controlled evaluation of lamotrigine as "add-on" treatment in DPD.

Adolescent↗