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Biomedical subjects

A M Mortimer

Publications and source records attributed to A M Mortimer.

At least 19 recordsLinked to original sources
PubMed1997

Cognitive function in schizophrenia--do neuroleptics make a difference?

Valid cognitive deficits in schizophrenia are now well characterised: general poor performance with disproportionate deficits in aspects of memory and executive function. Symptomatology, motivation, institutionalization, etc. cannot explain these deficits, which are of considerable importance for both the testing of theoretical models of schizophrenia and the determination of patients' functional outcome. The receptor blocking properties of neuroleptic treatments afford them the potential for interacting with monoaminergic, indoleaminergic, and cholinergic arousal systems in the brain and, hence, for modifying cognitive processes. However, the effects of conventional neuroleptics on cognition in schizophrenia are minor according to numerous studies. Atypical neuroleptics may, owing to their novel mechanisms of action, have the capacity to remediate cognitive impairment in schizophrenia: there is some evidence that clozapine has a "cognitive sparing" effect, but further research is needed in this area, particularly with other new drugs. Future studies should employ more appropriate methodology, particularly in terms of psychological/neurophysiological sophistication, patient evaluation, and applicability to real life, and should be hypothesis driven rather than purely empirical.

Animals↗
PubMed1996

Semantic memory is impaired in schizophrenia.

Memory is emerging as a key area of neuropsychological deficit in schizophrenia, with evidence suggesting that the impairment is restricted to long-term memory. Semantic memory, the component of long-term memory containing stored representations of the meanings of words and knowledge about the world, was examined in 46 schizophrenic patients and 40 normal controls using a recently devised battery of tests. Evidence of semantic memory impairment was found which was wide ranging and substantial; in some cases it approached the levels seen in a group of 22 patients with mild-to-moderate Alzheimer's disease. Both group analysis and a more detailed examination of two single cases suggested that semantic memory impairment represents a disproportionate and possibly specific neuropsychological deficit in schizophrenia.

Adolescent↗
PubMed1993

Memory in schizophrenia: what is impaired and what is preserved?

This study assesses the pattern of long-term memory performance in a sample of 12 schizophrenic patients who were selected on the basis of showing a memory deficit in the absence of gross overall intellectual impairment. When compared with 12 control subjects matched for age, sex and estimated premorbid IQ, presence of an episodic memory deficit was confirmed for both prose recall and forced-choice word and face recognition. Semantic memory was assessed using the sentence verification task developed by Collins and Quillian, an unpaced category judgement task, and the Mill Hill Vocabulary Scale. The schizophrenic patients were slower on sentence verification and they made significantly more errors in all three tasks. Procedural tasks included pursuit rotor performance, speed of repeatedly assembling a jigsaw puzzle and rate of improvement in reading transformed script. Here, while the schizophrenic patients showed poor overall performance on the pursuit rotor and jigsaw learning, their rate of learning on all three procedural tasks was comparable with that of the controls. When examined on two implicit memory tasks involving biasing of spelling of homophones and word stem completion, the patients showed a normal degree of priming in both. Implications for the nature of the memory deficit in schizophrenia are discussed.

Adolescent↗
PubMed1992

Memory impairment in schizophrenia: its extent, affiliations and neuropsychological character.

In a sample of 60 schizophrenic patients encompassing all grades of severity and chronicity memory impairment was found to be prevalent, often substantial, and disproportionate to the overall level of intellectual impairment. The deficits were not easily attributable to poor cooperation, attention or motivation; nor were they related to neuroleptic or anticholinergic medication. Memory impairment was significantly associated with severity and chronicity of illness and also with negative symptoms and formal thought disorder. There was evidence from the sample as a whole, and from a more detailed examination of five patients with relatively isolated deficits, that schizophrenic memory impairment conformed to the pattern seen in the classical amnesic syndrome. Additionally, there was preliminary evidence for a marked deficit in semantic memory.

Adult↗
PubMed1991

Motor, volitional and behavioural disorders in schizophrenia. 1: Assessment using the Modified Rogers Scale.

The assessment of catatonic symptoms, unlike that of other schizophrenia symptoms, has not acquired accuracy and phenomenological rigour, and their distinction from extrapyramidal side-effects is not always easy. The Modified Rogers Scale can rate abnormalities in movement, volition, speech, and overall behaviour in schizophrenia. It is detailed, reliable and valid, and permits the isolation of a score for non-extrapyramidal and hence presumably catatonic phenomena.

Arousal↗
PubMed1991

Motor, volitional and behavioural disorders in schizophrenia. 2: The 'conflict of paradigms' hypothesis.

An alternative to the conventional separation of extrapyramidal and catatonic symptoms exists in the 'conflict of paradigms' hypothesis, which proposes that there is a relative rather than absolute distinction between the two. The hypothesis predicts that a clinical association should exist between extrapyramidal and catatonic symptoms in schizophrenia. After rating 75 schizophrenic patients, a highly significant correlation between scores on the two classes of disorder was indeed found. This was composed of separate correlations between tardive dyskinesia and 'positive' catatonic phenomena, and Parkinsonism and 'negative' catatonic phenomena. The associations were not easily attributable to confounding factors and they were supported by factor analysis.

Adult↗
PubMed1990

Amnesic syndrome in schizophrenia.

Memory impairment is not usually considered to form part of the clinical picture of schizophrenia, except perhaps in severely deteriorated patients. In a survey of 60 patients encompassing all grades of severity and chronicity poor memory performance was found to be common, sometimes substantial, and disproportionately pronounced compared to the degree of general intellectual impairment. Although associated with severity and chronicity of illness, impaired memory was by no means confined to old, institutionalized, or markedly deteriorated patients. The pattern of deficit appeared to resemble that of the classic amnesic syndrome rather than that seen in Alzheimer-type dementia.

Adolescent↗
PubMed1990

Changes in the use of the Mental Health Act 1983 four years from its inception in Leeds Eastern Health Authority.

The origins of recent mental health legislation are briefly reviewed. Practices in the spirit rather than the letter of the 1983 Act are compared by studying one hundred periods of detention at its inception and another hundred four years later. There had been little change, and improvement only in rates of use of emergency powers and very short Section 2s.

Commitment of Persons with Psychiatric Disorders↗
PubMed1990

The positive:negative dichotomy in schizophrenia.

Two studies are reported. In the first, of 62 schizophrenic patients, no correlation between negative symptom scores (rated blindly) and any measure of positive symptoms was found. This independence was confirmed by factor and cluster analyses, which left the question of a third 'disorganisation' class of schizophrenic symptoms open. In the second study, of 80 patients, formal thought disorder separated unequivocally into 'positive formal thought disorder' and 'alogia' syndromes on the basis of correlations with positive and negative symptoms. Catatonic motor disorder also showed evidence of a corresponding positive: negative division, although this only emerged when severity or chronicity of illness was controlled for. Cognitive impairment showed a broad range of affiliations and its particular correlation with negative symptoms was perhaps artefactual.

Adult↗
PubMed1989

New probability matrices for identification of Streptomyces.

The character state data obtained for clusters defined in a previous phenetic classification were used to construct two probabilistic matrices for Streptomyces species. These superseded an original published identification matrix by exclusion of other genera and the inclusion of more Streptomyces species. Separate matrices were constructed for major and minor clusters. The minimum number of diagnostic characters for each matrix was selected by computer programs for determination of character separation indices (CHARSEP) and a selection of group diagnostic properties (DIACHAR). The resulting matrices consisted of 26 phena x 50 characters (major clusters) and 28 phena x 39 characters (minor clusters). Cluster overlap (OVERMAT program) was small in both matrices. Identification scores were used to evaluate both matrices. The theoretically best scores for the most typical example of each cluster (MOSTTYP program) were all satisfactory. Input of test data for randomly selected cluster representatives resulted in correct identification with high scores. The major cluster matrix was shown to be practically sound by its application to 35 unknown soil isolates, 77% of which were clearly identified. The minor cluster matrix provides tentative probabilistic identifications as the small number of strains in each cluster reduces its ability to withstand test variation. A diagnostic table for single-membered clusters, constructed using the CHARSEP and DIACHAR programs, was also produced.

Computers↗
PubMed1989

Detecting aberrant strains in bacterial groups as an aid to constructing databases for computer identification.

Computer assisted identification systems require that databases on the test results of the species are of high quality. One reason for poor quality is the inadvertent inclusion of strains that do not belong to a taxon; this can readily occur in groups where ancillary criteria (e.g. serology) are not available. A possible strategy is to exclude strains that are very atypical in their properties, i.e. that are very outlying, provided an objective criterion can be used. A computer program, OUTLIER, for the detection of outlying strains in bacterial clusters was evaluated. A brief description of the theory and operation of the program is given. The program uses as an objective criterion the degree to which the strain data fits a chi-square. This allows easy identification of aberrant strains that should be excluded in constructing a database. The program utilizes 1.0 data and calculations are based upon a choice of one of four identification coefficients. The relative merits of these four coefficients were examined for eight sets of bacterial data. Two of the coefficients, -log10 Willcox likelihood and Taxonomic distance squared appear to show little significant differences and we recommend these for routine work, with the first being the more useful. The Pattern distance squared was useful in indicating where atypical strains may be metabolically less active or slow-growing members of a cluster rather than true outliers. The Variance-weighted Taxonomic distance squared behaved anomalously and we do not recommend it.

Bacteria↗