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Biomedical subjects

A S David

Publications and source records attributed to A S David.

At least 109 records · Page 6Linked to original sources
PubMed1996

"Mirror, mirror on the wall, who...?": towards a model of visual self-recognition.

Self-recognition and self-awareness are processes fundamental to human development. This report describes the case of an 80-year-old woman who demonstrated the ''mirror sign'', an inability to recognise the reflection of oneself in a mirror. An attempt has been made to provide a cognitive neuropsychological explanation for this profound impairment in visual self-recognition, incorporating current cognitive theories of delusion formation and, specifically, delusions involving distorted appreciation of the self or others. We speculate that the impairment in visual self-recognition arises from deficits in visual and personal semantic memory related to bilateral hippocampal lesions, and that the greater extent of impairment in visual self-recognition compared with that for other familiar persons is possible evidence for a specific self-recognition process, represented as a separate ''self-identity node'' in the current face-processing model of Bruce and Young (1986).

Journal Article↗
PubMed1996

Auditory hallucinations inhibit exogenous activation of auditory association cortex.

Percepts unaccompanied by a veridical stimulus, such as hallucinations, provide an opportunity for mapping the neural correlates of conscious perception. Functional magnetic resonance imaging (fMRI) can reveal localized changes in blood oxygenation in response to actual as well as imagined sensory stimulation. The safe repeatability of fMRI enabled us to study a patient with schizophrenia while he was experiencing auditory hallucinations and when hallucination-free (with supporting data from a second case). Cortical activation was measured in response to periodic exogenous auditory and visual stimulations using time series regression analysis. Functional brain images were obtained in each hallucination condition both while the patient was on and off antipsychotic drugs. The response of the temporal cortex to exogenous auditory stimulation (speech) was markedly reduced when the patient was experiencing hallucinating voices addressing him, regardless of medication. Visual cortical activation (to flashing lights) remained normal over four scans. From the results of this study and previous work on visual hallucinations we conclude that hallucinations coincide with maximal activation of the sensory and association cortex, specific to the modality of the experience.

Acoustic Stimulation↗
PubMed1996

Editorial.

Explore the source record for details and available documents.

Editorial↗
PubMed1996

Stroop interference and facilitation in the cerebral hemispheres in schizophrenia.

A divided visual field presentation of the Stroop colour-word test was used to study interhemispheric (transcallosal) function in schizophrenic and normal subjects. The modified test used a colour strip paired with either an incongruent, neutral or congruent colour word. Interference and facilitation were defined as the difference between the mean reaction times for incongruent stimuli and neutral stimuli and that between neutral stimuli and congruent stimuli, respectively. The stimuli were presented tachistoscopically with the two components either separated across the midline centrally, up or down from the midpoint (bilateral presentation), or presented to a single visual half-field (unilateral presentation). The inclusion of the 'up' and 'down' bilateral conditions controlled for the reaction time advantage for central compared with unilateral stimulus presentations noted in an earlier study (David, 1993a). The difference in reaction time to an incongruent compared with a congruent colour-word pairing, the Combined Stroop Effect (CSE), was not affected significantly by stimulus presentation position (bilateral vs. unilateral) in either the control or schizophrenic group, unlike in the earlier study of David. For controls, interference was significantly greater than facilitation for both bilaterally- and unilaterally-presented stimuli. Schizophrenics had a significantly smaller interference effect for bilaterally-presented stimuli, indicating reduced interhemispheric interference in this group. For the control group, there was no significant difference between right and left CSEs, interference being significantly greater than facilitation on both visual half-field presentations. For schizophrenics, the CSE for left-presented stimuli was significantly greater than that for right-presented stimuli. In addition, left-field facilitation was significantly greater than right-field. Reduced Stroop facilitation with right-field presentations in schizophrenic subjects may reflect increased vulnerability of colour-naming by word-reading in the left hemisphere-evidence for the non-unitary nature of attentional processes and disintegration of these in schizophrenia.

Adult↗
PubMed1996

Functional echoplanar brain imaging correlates of amphetamine administration to normal subjects and subjects with the narcoleptic syndrome.

Two subjects with narcoleptic syndrome and three healthy volunteers underwent functional magnetic resonance imaging during the simultaneous presentation of periodic auditory and visual stimuli both before and after administration of amphetamine. The effect of amphetamine in control subjects was a small reduction in the extent of sensory-induced activation. In the narcoleptic subjects, amphetamine led to an increase in the extent of induced activation within primary and association sensory cortex.

Acoustic Stimulation↗
PubMed1996

Functional anatomy of inner speech and auditory verbal imagery.

The neural correlates of inner speech and of auditory verbal imagery were examined in normal volunteers, using positron emission tomography (PET). Subjects were shown single words which they used to generate short, stereotyped sentences without speaking. In an inner speech task, sentences were silently articulated, while in an auditory verbal imagery condition, subjects imagined sentences being spoken to them in an another person's voice. Inner speech was associated with increased activity in the left inferior frontal gyrus. Auditory verbal imagery was associated with increases in the same region, and in the left premotor cortex, the supplementary motor area and the left temporal cortex. The data suggest that the silent articulation of sentences involves activity in an area concerned with speech generation, while imagining speech is associated with additional activity in regions associated with speech perception.

Adult↗
PubMed1996

The auditory hallucination: a phenomenological survey.

A comprehensive semi-structured questionnaire was administered to 100 psychotic patients who had experienced auditory hallucinations. The aim was to extend the phenomenology of the hallucination into areas of both form and content and also to guide future theoretical development. All subjects heard 'voices' talking to or about them. The location of the voice, its characteristics and the nature of address were described. Precipitants and alleviating factors plus the effect of the hallucinations on the sufferer were identified. Other hallucinatory experiences, thought insertion and insight were examined for their inter-relationships. A pattern emerged of increasing complexity of the auditory-verbal hallucination over time by a process of accretion, with the addition of more voices and extended dialogues, and more intimacy between subject and voice. Such evolution seemed to relate to the lessening of distress and improved coping. These findings should inform both neurological and cognitive accounts of the pathogenesis of auditory hallucinations in psychotic disorders.

Adaptation, Psychological↗
PubMed1995

Adverse life events and breast cancer: case-control study.

OBJECTIVE: To investigate the strength of association between past life events and the development of breast cancer. DESIGN: Case-control study. A standardised life events interview and rating was administered before a definitive diagnosis. SETTING: Breast Cancer Screening Assessment Unit and surgical outpatient clinics at King's College Hospital, London. SUBJECTS: 119 consecutive women aged 20-70 who were referred for biopsy of a suspicious breast lesion. MAIN OUTCOME MEASURES: Odds ratio of the risk of developing breast cancer after life events in the preceding five years after adjustment for confounders. RESULTS: 41 women were diagnosed as having malignant disease while the remainder had benign conditions. Severe life events increased the risk of breast cancer. The crude odds ratio was 3.2 (95% confidence interval 1.35 to 7.6). After adjustment for age and the menopause and other potential confounders this rose to 11.6 (3.1 to 43.7). Multiple logistic regression analysis showed that all severe events and coping with the stress of adverse events by confronting them and focusing on the problems significantly predicted a diagnosis of breast cancer. Non-severe life events and long term difficulties had no significant association. CONCLUSION: These findings suggest an aetiological association between life stress and breast cancer.

Adaptation, Psychological↗
PubMed1995

Schizophrenic auditory hallucinations are associated with increased regional cerebral blood flow during verbal memory activation in a study using single photon emission computed tomography.

Single photon emission tomography with split-dose technetium-99m-d, l-hexamethyl-propylene amine oxime was used to measure regional cerebral blood flow (rCBF) during a memory-activation paradigm in a group of 18 medicated DSM-III-R schizophrenic patients. The relationship between clinical features of schizophrenia and rCBF patterns was examined. Increased blood flow to the left basal ganglia was revealed during activation in patients reporting hallucinations in the previous month, a finding that was not influenced by medication dose or other confounding variables. This result adds to previous functional imaging studies that have related basal ganglia abnormalities to hallucinatory phenomena and suggests that left basal ganglia hyperactivity may be relevant to an internal monitoring deficit responsible for the appearance of those symptoms in schizophrenia.

Adult↗
PubMed1995

Abnormal monitoring of inner speech: a physiological basis for auditory hallucinations.

Auditory verbal hallucinations ("voices") are thought to arise from a disorder of inner speech (thinking in words). We examined the neural correlates of tasks which involve inner speech in subjects with schizophrenia who hear voices (hallucinators), subjects with schizophrenia who do not (nonhallucinators), and normal controls. There were no differences between hallucinators and controls in regional cerebral blood flow during thinking in sentences. However, when imagining sentences being spoken in another person's voice--which entails both the generation and monitoring of inner speech--hallucinators had a normal left frontal response, but reduced activation in the left middle temporal gyrus and the rostral supplementary motor area, regions which were activated by both normal subjects and nonhallucinators (p < 0.001). These findings suggest that a predisposition to verbal hallucinations is associated with a failure to activate areas concerned with the monitoring of inner speech.

Adult↗
PubMed1995

Facial processing in schizophrenia and delusional misidentification: cognitive neuropsychiatric approaches.

The human face is of great importance as a stimulus in view of the detailed information it contains--information vital to understand in order to survive in the complex social world. There are different aspects to facial processing, including: affect analysis, recognition of individuality and recognition of familiarity, all of which have been incorporated into the cognitive model of Bruce and Young (1986). The cognitive neuropsychiatric approach has recently been employed in the study of facial processing in schizophrenia. It has become apparent that schizophrenic subjects are impaired in facial processing tasks at all levels, and this may well be related to the misinterpretation of social interactions commonly found in such subjects. This approach has also led to a greater understanding of delusional misidentification, with particular syndromes explained in terms of processing deficits at different levels of the cognitive model above. At an anatomical level, the role of the right hemisphere in facial perception is well-known, with there being some evidence of right hemisphere hypofunction in subjects with schizophrenia and also in delusional misidentification. The review therefore emphasizes the importance of the neuropsychiatric approach for further investigation of facial processing and understanding of symptomatology in schizophrenia and related psychoses.

Capgras Syndrome↗
PubMed1995

Cognitive features of psychotic states arising in late life (late paraphrenia).

The cognitive performance of 47 elderly psychotic patients with onset of symptoms in late life (late paraphrenia) was compared to that of 33 controls matched for age, sex, ethnic origin, number of years of education, and pre-morbid IQ as measured by the NART. Neuropsychological indices of general cognitive functioning (MMSE, CAMCOG, WAIS-R verbal and performance scores) showed that patients were performing the tasks at a significantly lower level than controls. Patients also showed a trend to have a lower span capacity than controls, particularly at the spatial span subtest. There was no obvious impairment of learning as measured by the digit and spatial recurring span tasks nor of simultaneous matching-to-sample ability. However, patients' performance on a delayed-matching-to-sample procedure was significantly worse than that of controls. In addition, patients performed worse than controls on the Recognition Memory Test for Faces, but not for Words. Finally, the performance of patients on tests assessing executive functioning (Verbal Fluency Test, Computerized Extra and Intra-Dimensional Shift Task, Computerized Spatial Working Memory Task, and Computerized Tower of London Task) was consistently worse than that of controls. These results suggest that psychotic states arising in late life are predominantly associated with a decline on measures of general cognitive ability and executive functioning. The neuropsychological meaning of these findings is discussed in the light of cognitive models of psychotic symptoms, as well as of schizophrenia and dementia research. We concluded that the lack of a clear pattern of impairment among these patients may be the result of their clinical and cognitive diversity.

Aged↗
PubMed1995

Clinical and cognitive diversity of psychotic states arising in late life (late paraphrenia).

This study aimed to explore the heterogeneity of paranoid psychosis with onset in late life by using cognitive factors in a centroid method of cluster analysis. Forty-seven subjects were allocated to two different clusters, the first with 24 (51.1%) and the second with 23 (48.9%) patients. Their cognitive attainment was evaluated against the performance of 33 elderly controls, all groups being matched for age, sex, and the numbers of years of education. Patients in cluster 2 showed a pattern of widespread cognitive impairment, which involved general measures of cognitive performance (MMSE, CAMCOG, WAIS-R verbal and performance scores), memory (digit and spatial span, delayed matching-to-sample, recognition memory for words and faces), and executive functions (verbal fluency, extra and intra-dimensional shift ability, spatial working memory, and planning). In contrast, patients in cluster 1 were only impaired on their extra-dimensional set shift and planning abilities, suggesting a more specific and restricted executive functioning deficit. We also analysed the impact that the use of antipsychotic medication could have had on patients' cognitive performance, which was shown to be negligible. In addition, there was no difference between the clusters with regard to the number of patients using neuroleptics, suggesting that the medication was unlikely to have introduced a performance bias in the two patient clusters. The validity of the subdivision of these patients into two separate groups was further supported by other clinical findings. Patients in cluster 1 exhibited more severe psychotic symptoms, as measured by the SAPS, than their counterparts in cluster 2, and were also more likely to display first-rank symptoms of Schneider. Conversely, cluster 2 membership was strongly associated with the presence of neurological signs and negative symptoms. We suggest that psychotic states arising in late life are a heterogeneous condition that may be best divided in two: 'type A', including patients with a wide range of psychotic symptoms, mild increase in the frequency of neurological signs, and cognitive deficits restricted to executive functions, and 'type B', which includes patients with less complex psychotic symptoms associated with a marked increase in the frequency of neurological signs and generalized cognitive impairment. The basis for this subdivision and the prospect for future studies are discussed.

Aged↗
PubMed1995

Meta-analysis of corpus callosum size in schizophrenia.

Studies with MRI have shown differences in corpus callosum size between schizophrenic patients and controls. Most have found that the corpus callosum is smaller in schizophrenic patients, but in only a minority was this finding statistically significant, perhaps due to small sample sizes. Therefore a meta-analysis of 11 published studies of corpus callosum morphology in schizophrenia was conducted to ascertain whether there was a significant difference in corpus callosum size between schizophrenic patients and normal controls. These studies combined comprised 313 patients and 281 controls. Measures of corpus callosum midsagittal area, length, and corpus callosum area:brain area ratio were used in the meta-analysis. There was overall a statistically significant reduction in corpus callosum area in schizophrenic patients compared with controls (P < 0.02). Differences between patients and controls in measures of corpus callosum: brain area and corpus callosum length were not statistically significant. Age and corpus callosum area were related in both patients and controls. The influences on the corpus callosum of overall alterations of brain size, sex, handedness, and psychiatric illness in general remains to be determined.

Adult↗
PubMed1995

Psychotic states arising in late life (late paraphrenia) psychopathology and nosology.

BACKGROUND: This study explored the psychopathological state of a sample of 'late paraphrenic' patients and the reliability of their diagnosis according to the most widely used systems of classification of mental disorders. METHOD: The presence and severity of psychiatric symptoms were assessed with the Present State Examination (PSE), the Scale for the Assessment of Positive Symptoms (SAPS), and the High Royds Evaluation of Negativity (HEN) scale. Patient signs and symptoms were classified according to the PSE9-CATEGO4, DSM-III-R, DSM-IV, and ICD-10 diagnostic systems. Agreement among the 11 most widely used criteria for the diagnosis of schizophrenia was assessed for these patients. These included DSM-III-R, DSM-IV, ICD-10, Schneider, Langfeldt, New Haven Schizophrenia Index, Carpenter, Research Diagnostic Criteria (RDC), Feighner, Taylor & Abrams, and PSE9-CATEGO4. The study assessed 47 patients, including in-patients, out-patients, day-patients, and those in the community. Thirty-three elderly controls were recruited from luncheon clubs in Southwark and Lambeth (London, UK). RESULTS: Patients showed a wide range of delusional ideas, most frequently involving persecution (83.0%) and reference (31.9%). Eighty-three per cent of patients reported some sort of hallucination, most frequently auditory (78.7%). Formal thought disorder was very rare, only one patient showing mild signs of circumstantial speech. No patients exhibited catatonic symptoms or inappropriate affect. Shallow, withdrawn, or constricted affect was found in only 8.5% of patients. The various systems of classification indicated that most patients displayed typical schizophrenic symptoms, although up to one-third of them did not meet criteria for the diagnosis of schizophrenia. There was poor agreement among the different diagnostic schedules as to whether to classify patients as schizophrenic (0.02 < k < 0.45). CONCLUSION: Psychotic states arising in late life are accompanied by various psychiatric symptoms that are not entirely typical of early-onset schizophrenia. The current trend to include 'late paraphrenia' into the diagnosis of schizophrenia or delusional disorder has poor empirical and theoretical bases.

Age of Onset↗