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Biomedical subjects

A S David

Publications and source records attributed to A S David.

At least 55 records · Page 3Linked to original sources
PubMed2001

Cognitive neuropsychiatry: towards a scientific psychopathology.

Cognitive neuropsychiatry represents a systematic and theoretically driven approach to explain clinical psychopathologies in terms of deficits to normal cognitive mechanisms. A concern with the neural substrates of impaired cognitive mechanisms links cognitive neuropsychiatry to the basic neurosciences. The emergence of cognitive neuropsychiatry in the 1990s illustrates the growing rapprochement between cognitive neuropsychology, clinical medicine and the neurosciences in addressing common questions about disorders of the mind/brain. In reviewing recent applications, we highlight how this hybrid discipline will make a distinctive contribution to the science of psychopathology.

Brain↗
PubMed2001

Visual hallucinations in Parkinson's disease: a review and phenomenological survey.

OBJECTIVES: Between 8% and 40% of patients with Parkinson's disease undergoing long term treatment will have visual hallucinations during the course of their illness. There were two main objectives: firstly, to review the literature on Parkinson's disease and summarise those factors most often associated with hallucinations; secondly, to carry out a clinical comparison of ambulant patients with Parkinson's disease with and without visual hallucinations, and provide a detailed phenomenological analysis of the hallucinations. METHODS: A systematic literature search using standard electronic databases of published surveys and case-control studies was undertaken. In parallel, a two stage questionnaire survey was carried out based on members of a local branch of the Parkinson's Disease Society and followed up with a clinical interview. RESULTS: The review disclosed common factors associated with visual hallucinations in Parkinson's disease including greater age and duration of illness, cognitive impairment, and depression and sleep disturbances. The survey comprised 21 patients with visual hallucinations and 23 without. The hallucinators had a longer duration and a greater severity of illness, and tended to show more depressed mood and cognitive impairment. The typical visual hallucination in these patients is a complex visual image experienced while they are alert and have their eyes open. The image appears without any known trigger or voluntary effort, is somewhat blurred, and commonly moves. It stays present for a period of "seconds" or "minutes". The content can be variable within and between hallucinators, and includes such entities as people, animals, buildings, or scenery. These features resemble those highlighted in hallucinations in the visually impaired (Charles Bonnet's syndrome). CONCLUSION: A consistent set of factors are associated with visual hallucinations in Parkinson's disease. The results of the phenomenological survey and those of visual hallucinations carried out in other settings suggest a common physiological substrate for visual hallucinations but with cognitive factors playing an as yet unspecified role.

Aged↗
PubMed2001

Systematic meta-review of depot antipsychotic drugs for people with schizophrenia.

BACKGROUND: Long-acting depot antipsychotic medication is a widely used treatment for schizophrenia. AIMS: To synthesise relevant systematic Cochrane reviews. METHOD: The Cochrane Database was searched and summary data were extracted from randomised controlled clinical trials of depots. RESULTS: Standard dose depot v. placebo resulted in significantly less relapse but more movement disorders. Those on depots (v. oral drugs) showed more global change on one outcome measure; relapse and adverse effects showed no difference. Comparisons showed no convincing advantages for one depot over another. CONCLUSIONS: Depot antipsychotics are safe and effective. They may confer a small benefit over oral drugs on global outcome. Those for whom depots are most indicated may not be represented. Large studies are required to discern differences in relapse rates and long-term adverse effects, and data on satisfaction, quality of life and economics.

Administration, Oral↗
PubMed2001

Systematic review of patient and nurse attitudes to depot antipsychotic medication.

BACKGROUND: Depot antipsychotic medication is used widely in the treatment and prophylaxis of severe mental illness. AIMS: To review the literature on patient and nurse satisfaction with, and attitudes towards, depots. METHOD: A systematic search of Medline, Embase, PsycINFO, CINAHL and The Cochrane Library was undertaken, along with citation searches. Studies were selected if satisfaction/attitude data were described in the title or abstract and original data were included. Study quality was rated. RESULTS: The search produced 1374 articles; 22 articles met the inclusion criteria, 18 of which were cross-sectional surveys. Of the 12 studies with relevant data, 10 conveyed a positive opinion of depot medication. Five out of six studies comparing depot with oral medication showed patient preference for depot. CONCLUSIONS: High-quality data examining patient and nurse attitudes regarding depot antipsychotics are sparse. What data there are show a positive attitude to depots from patients. Future randomised controlled trials should include satisfaction as an outcome.

Administration, Oral↗
PubMed2001

Signs of asphyxia at birth and risk of schizophrenia. Population-based case-control study.

BACKGROUND: Previous research has found an association between obstetric complications and schizophrenia, but in many studies the sample size was limited, and no assessment of specific exposures was possible. AIMS: To assess the role of different complications, and in particular to distinguish between disordered foetal development and hypoxia at birth. METHOD: From the Stockholm County In-Patient Register and community registers, we identified 524 cases of schizophrenia and 1043 controls, matched for age, gender, hospital and parish of birth. Data on obstetric complications were obtained from birth records. RESULTS: There was a strong association between signs of asphyxia at birth and schizophrenia (OR 4.4; 95% C11.9-10.3) after adjustment for other obstetric complications, maternal history of psychotic illness and social class. CONCLUSIONS: Signs of asphyxia at birth are associated with an increased risk of schizophrenia in adults.

Adolescent↗
PubMed2001

Obstetric complications and risk of schizophrenia. Effect of gender, age at diagnosis and maternal history of psychosis.

BACKGROUND: Obstetric complications have been studied frequently as possible risk factors for schizophrenia. AIMS: To test the hypotheses that individual obstetric complications are most strongly associated with an increased risk of schizophrenia in males, in patients with an early age at first diagnosis and in subjects with a maternal history of psychosis. METHOD: Cases of schizophrenia diagnosed between January 1971 and June 1994 were identified in the Stockholm County In-Patient Register. Controls were matched on age, gender, hospital of birth and parish of birth. Obstetric data were recorded blind to case-control status for 524 cases and 1043 controls. RESULTS: This study did not find any large or consistent effect of gender, age at diagnosis or maternal history of psychosis on the risk of schizophrenia associated with individual complications. CONCLUSIONS: Future studies should examine these effects using a much larger sample that includes patients with schizophrenia and control subjects whose genetic risk of schizophrenia has been assessed accurately.

Adolescent↗
PubMed2000

Silent speechreading in the absence of scanner noise: an event-related fMRI study.

In a previous study we used functional magnetic resonance imaging (fMRI) to demonstrate activation in auditory cortex during silent speechreading. Since image acquisition during fMRI generates acoustic noise, this pattern of activation could have reflected an interaction between background scanner noise and the visual lip-read stimuli. In this study we employed an event-related fMRI design which allowed us to measure activation during speechreading in the absence of acoustic scanner noise. In the experimental condition, hearing subjects were required to speechread random numbers from a silent speaker. In the control condition subjects watched a static image of the same speaker with mouth closed and were required to subvocally count an intermittent visual cue. A single volume of images was collected to coincide with the estimated peak of the blood oxygen level dependent (BOLD) response to these stimuli across multiple baseline and experimental trials. Silent speechreading led to greater activation in lateral temporal cortex relative to the control condition. This indicates that activation of auditory areas during silent speechreading is not a function of acoustic scanner noise and confirms that silent speechreading engages similar regions of auditory cortex as listening to speech.

Adult↗
PubMed2000

The functional neuroanatomy of implicit-motion perception or representational momentum.

BACKGROUND: When we view static scenes that imply motion - such as an object dropping off a shelf - recognition memory for the position of the object is extrapolated forward. It is as if the object in our mind's eye comes alive and continues on its course. This phenomenon is known as representational momentum and results in a distortion of recognition memory in the implied direction of motion. Representational momentum is modifiable; simply labelling a drawing of a pointed object as 'rocket' will facilitate the effect, whereas the label 'steeple' will impede it. We used functional magnetic resonance imaging (fMRI) to explore the neural substrate for representational momentum. RESULTS: Subjects participated in two experiments. In the first, they were presented with video excerpts of objects in motion (versus the same objects in a resting position). This identified brain areas responsible for motion perception. In the second experiment, they were presented with still photographs of the same target items, only some of which implied motion (representational momentum stimuli). When viewing still photographs of scenes implying motion, activity was revealed in secondary visual cortical regions that overlap with areas responsible for the perception of actual motion. Additional bilateral activity was revealed within a posterior satellite of V5 for the representational momentum stimuli. Activation was also engendered in the anterior cingulate cortex. CONCLUSIONS: Considering the implicit nature of representational momentum and its modifiability, the findings suggest that higher-order semantic information can act on secondary visual cortex to alter perception without explicit awareness.

Adult↗
PubMed2000

Patterns of referral in patients with medically unexplained motor symptoms.

OBJECTIVE: To investigate the pattern and reasons for referrals in 64 patients with a stable diagnosis of motor conversion symptoms who had been assessed at the National Hospital for Neurology and Neurosurgery (NHNN). METHOD: Patients were interviewed on average 6 years after their original admission to the NHNN. Hospital notes and GP records were consulted. RESULTS: Psychiatrists at the NHNN saw 75% of patients. Treatment was initiated in 60% of these. During the 6-year follow up, many patients continued to be referred to neurologists and other specialists, but subsequent psychiatric referral was rare. Many changed their GP after discharge from the NHNN and a disproportionate number of re-referrals was made by GPs who had known their patients for less than 6 months. Psychological attribution of symptoms was rare and did not appear to be related to the pattern of referrals. CONCLUSION: The pattern of care of these patients was inconsistent and many felt dissatisfied with the treatment they received. This led to further referrals, unnecessary use of valuable resources and unnecessary exposure to iatrogenic damage. Further studies should aim to assist GPs and other clinicians in deciding when referral is likely to be beneficial.

Adult↗
PubMed2000

Cortical activity during rotational and linear transformations.

Neuroimaging studies of cortical activation during image transformation tasks have shown that mental rotation may rely on similar brain regions as those underlying visual perceptual mechanisms. The V5 complex, which is specialised for visual motion, is one region that has been implicated. We used functional magnetic resonance imaging (fMRI) to investigate rotational and linear transformation of stimuli. Areas of significant brain activation were identified for each of the primary mental transformation tasks in contrast to its own perceptual reference task which was cognitively matched in all respects except for the variable of interest. Analysis of group data for perception of rotational and linear motion showed activation in areas corresponding to V5 as defined in earlier studies. Both rotational and linear mental transformations activated Brodman Area (BA) 19 but did not activate V5. An area within the inferior temporal gyrus, representing an inferior satellite area of V5, was activated by both the rotational perception and rotational transformation tasks, but showed no activation in response to linear motion perception or transformation. The findings demonstrate the extent to which neural substrates for image transformation and perception overlap and are distinct as well as revealing functional specialisation within perception and transformation processing systems.

Adult↗
PubMed2000

Towards a functional neuroanatomy of self processing: effects of faces and words.

We studied the neural correlates of self vs. non-self judgements using functional magnetic resonance imaging (fMRI). Individually tailored faces and personality trait words were used as stimuli in three experiments (exp.). In the first two experiments, brain activation was measured while subjects viewed morphed versions of either their own (self face exp.) or their partner's face (partner's face exp.), alternating in blocks with presentation of an unknown face. In the self face exp. right limbic areas (hippocampal formation, insula, anterior cingulate), the right middle temporal lobe, left inferior parietal and left prefrontal regions showed signal changes. In the partner's face exp., only the right insula was activated. In the third exp., subjects made decisions about psychological trait adjectives previously categorized as describing their own attributes. Activation was present in the precuneus, the left parietal lobe, left insula/inferior frontal gyrus and the left anterior cingulate. A reaction time advantage was present when subjects responded to self-relevant words. The main area with signal changes during self-reference processing, regardless of the type of stimulus, was the left fusiform gyrus. The self-relevant stimuli engaged to a differential extent long term and working memory, semantic and emotional processes. We suggest that regions activated by these stimuli are engaged in self-processing.

Adult↗
PubMed2000

Sensitivity to linguistic anomalies in spoken sentences: a case study approach to understanding thought disorder in schizophrenia.

BACKGROUND: As a group, positively thought-disordered (TD) schizophrenic patients are relatively impaired in their ability to use linguistic context to process sentences online (Kuperberg et al. 1998). This study investigates the heterogeneity in the use of linguistic context both between individual TD patients and within the individual patients as severity of thought disorder changes over time. METHODS: Seventeen TD schizophrenics performed an online word-monitoring task on four separate occasions. In each patient, baseline reaction time (RTs) to target words in normal sentences were subtracted from RTs to target words in pragmatically-, semantically- and syntactically-violated sentences to obtain a measure of online sensitivity to each type of linguistic violation, and these were compared with normative data of a healthy volunteer and a non-TD schizophrenic control group. In addition, the co-variation of severity of thought disorder and sensitivity to linguistic context within all individual TD patients over the four testing sessions, was examined. RESULTS: There was marked heterogeneity between individual TD patients in their sensitivity to different types of linguistic violations: some were selectively insensitive to pragmatic violations, while others were insensitive to semantic and syntactic (subcategorization) violations. There was also an inverse relationship between severity of thought disorder and sensitivity to linguistic violations within individual patients over the four sessions. CONCLUSIONS: It is likely that a single cognitive deficit does not account for all types of schizophrenic thought disorder, but rather that there are multiple deficits affecting specific levels of linguistic processing. In these schizophrenic patients, impairment in the use of linguistic context was related to the state, rather than the trait, of thought disorder.

Adolescent↗
PubMed2000

Perception of threat in schizophrenics with persecutory delusions: an investigation using visual scan paths.

BACKGROUND: Cognitive theories of persecutory delusions in schizophrenia include increased attention to threat and reduced re-appraisal of information during decision-making. METHODS: We employed visual scan path measurements, an 'on-line' marker of attention, in schizophrenic patients with persecutory delusions (N = 19), negative symptom- and medication-matched patients with non-persecutory delusions (N = 8), and normal controls (N = 18). Stimuli comprised black-and-white photographs of social scenes rated as depicting either neutral, ambiguous or overtly threatening activity. Foreground areas containing salient information with regard to the overall scene were rated independently as either threatening or non-threatening in both the overtly threatening and ambiguous scenes; all foreground areas were rated as non-threatening in the neutral scene. RESULTS: For the ambiguous scene only, schizophrenics with persecutory delusions directed gaze to less threatening areas, and, for all three scenes, demonstrated reduced re-appraisal of information compared with both control groups. All subjects showed similar viewing strategies for the overtly threatening and neutral scenes. CONCLUSIONS: These findings suggest abnormal information gathering and evaluation in schizophrenics, specifically related to the presence of persecutory delusions. In particular, the results point to biased processing of contextual information in an ambiguous setting in these patients, and perhaps perception of threat in inappropriate places.

Adult↗
PubMed2000

Is auditory imagery defective in patients with auditory hallucinations?

BACKGROUND: A variant of the 'inner speech' theory of auditory verbal hallucinations in schizophrenia suggests that there is an abnormality of the relationship between the 'inner voice' and 'inner ear', such that hallucinators are unable to distinguish inner 'imagined' speech from real external speech, and so misrecognize inner speech as alien. METHODS: Five experiments were carried out comparing 12 schizophrenic patients who were highly prone to hallucinate, with seven patients who were not, on a series of auditory imagery tasks that are differentially dependent on inner voice/inner ear partnership for successful performance: parsing meaningful letter/number strings; the verbal transformation effect; phoneme judgements; pitch judgements, and homophony and rhyme judgements. RESULTS: Contrary to our hypothesis, there was no evidence that the group with the propensity to hallucinate were impaired on tasks requiring normal inner ear/inner voice partnership. CONCLUSIONS: Together with previous work indicating no impairment of the phonological loop in patients who hallucinate, these results suggest that inner speech and auditory verbal hallucinations are not connected in a simplistic or direct way. Indeed, a reappraisal of psychological models of hallucinations in general may be warranted.

Adolescent↗
PubMed2000

Delay in presentation of symptomatic referrals to a breast clinic: patient and system factors.

We attempted to identify factors associated with delay in presentation and assessment of women with breast symptoms who attended a London breast clinic. A total of 692 consecutive symptomatic referrals, aged 40-75 years, were studied. Patient delay, assessed prior to diagnosis, was defined as time elapsing between symptom discovery and first presentation to a medical provider. This was studied in relation to: reasons for delaying, beliefs and attitudes, socio-demographic and clinical variables, psychiatric morbidity and subsequent diagnosis. Thirty-five per cent of the cohort delayed presentation 4 weeks or more (median 13 days). The most common reason given was that they thought their symptom was not serious (odds ratio (OR) = 5.32, 95% confidence interval (CI) 3.6-8.0). Others thought their symptom would go away (OR = 3.73, 95% CI 2.2-6.4) or delayed because they were scared (OR = 4.61, 95% CI 2.1-10.0). Delay was associated with psychiatric morbidity but not age. Patients who turned out to have cancer tended to delay less (median 7 days) but not significantly. Median system delay--time between first medical consultation and first clinic visit--was 18 days. Patients who thought they had cancer and those so diagnosed were seen more promptly (median 14 days). Most factors, including socio-economic status and ethnicity were non-contributory. Beliefs about breast symptoms and their attribution are the most important factors determining when women present. Health education messages should aim to convince symptomatic women that their condition requires urgent evaluation, without engendering fear in them.

Adult↗