Reversed cerebral asymmetry and breast cancer.
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Breast Neoplasms↗
Biomedical subjects
I C McManus
Publications and source records attributed to I C McManus.
Are paw preference differences in HI and LO mice the result of specific genes or of heterosis and fluctuating asymmetry?
Collins (1985) has described two separate mouse strains, obtained by selective breeding, which differ in having high (HI) or low (LO) degrees of paw preference on a standard test. In this paper I argue that the differences between these strains may not be due to a specific gene (or genes) but, instead, probably reflect differences in the total heterozygosity of the strains, such that the HI strain is more heterotic than the LO strain. Greater degrees of heterozygosity are argued to buffer against fluctuating asymmetry and hence result in a greater degree of paw preference.
Animals↗
Handedness in childhood autism shows a dissociation of skill and preference.
Hand preference and hand skill were assessed in 20 children with autism, 20 normal controls and 12 children with mental retardation. 90% of the normal controls and 92% of the children with mental retardation showed concordance for hand preference and hand skill (i.e. the preferred hand was also the more skillful), whereas only 50% of the children with autism showed concordance of preference and skill, the remaining 50% preferring to use the hand which was less skillful. Children with autism also showed a lesser degree of handedness and a lesser degree of consistency than the other groups, although this was unrelated to the discordance of skill and asymmetry. A developmental model of handedness is proposed in which the development of handedness as preference is ontogenetically prior to the development of handedness as skill asymmetry, such that in normal children the development of skill asymmetry occurs as a secondary consequence of the establishment of preference. The causal sequence is disrupted in autism, so that although preference is established, it does not subsequently result in concordant skill asymmetry.
Autistic Disorder↗
The anxieties of new clinical students.
The specific anxieties of 74 medical students beginning their clinical training were assessed by means of a questionnaire at the start of the clinical introductory course at St Mary's Hospital Medical School, London. Situations differed in the amount of anxiety that they engendered, and students also differed in the number of situations that they found anxiety producing. Students particularly reported that interactions with senior staff on ward rounds were anxiety provoking. The same questionnaire was also distributed to 52 teaching hospital doctors who were asked to complete the questionnaire as they thought the students had done. Compared with students, the doctors considered more situations to be anxiety provoking, and they differed in their rank ordering of the situations. Doctors tended to overestimate anxiety concerning communication problems, and to underestimate anxiety concerning routine clinical tasks such as phlebotomy.
Anxiety↗
Does performance improve when candidates resit a postgraduate examination?
Luck plays some role in passing any examination. When candidates pass a postgraduate examination at the second, third or subsequent attempt is it because their knowledge has truly improved or because they have at least been lucky? In this paper a simple model, requiring knowledge only of the pass rates at resits, and of the reliability of the examination, is applied to the MRCGP examination of the Royal College of General Practitioners. Candidates increase their true ability before second and third attempts at the examination, after which ability declines.
Clinical Competence↗
Ventricular enlargement in schizophrenia. A meta-analysis of studies of the ventricle:brain ratio (VBR)
Multivariate meta-analysis was performed on 39 studies of ventricular size in schizophrenia which used the ventricle:brain ratio (VBR). The size of the VBR was dependent both upon the date when studies were carried out (more recent studies showing a reduction in the difference between schizophrenics and controls), and upon the diagnostic criterion used in the studies. Methodological factors in study design seemed more important than the characteristics of the schizophrenic subjects, in determining the VBR. Our analysis suggests that there is a difference in VBR between schizophrenics and controls which would seem to be an indisputable characteristic of schizophrenia. However, the difference is smaller than has previously been thought, so that, although of undoubted theoretical interest in accounting for the aetiology of schizophrenia, it is probably too small to be of practical significance in diagnosis, or in the differentiation of subtypes.
Brain↗
How will medical education change?
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Curriculum↗
Membership examinations and Royal College finances.
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Accreditation↗
The inheritance of left-handedness.
Left-handedness occurs in about 8% of the human population. It runs in families and an adoption study suggests a genetic rather than an environmental origin; however, monozygotic twins show substantial discordance. The only genetic models that successfully explain the family and twin data are those of McManus and Annett, which share the feature of incorporating a random component reflecting the biological phenomenon of 'fluctuating asymmetry'. The models have each been modified to explain the greater incidence of left-handedness in males. The McManus model is more successful at explaining the maternal effect--left-handed mothers have more left-handed offspring than do left-handed fathers. Both models explain the association of handedness with cerebral language dominance. The models differ principally in their conception of the phenotypes of handedness: Annett proposes a unimodal continuum, McManus proposes two discrete categories of handedness. Finding the gene for handedness and hence for language dominance would unlock the neurobiology of language. Two ways of finding the gene for handedness are proposed: searching the pseudoautosomal region of the X chromosome or invoking a specific evolutionary model of lateralization in which the handedness gene has evolved from the situs gene then searching the human genome for homologues to the mouse situs gene.
Animals↗
Handedness is not related to self-reported disease incidence.
A hand preference inventory and a disease questionnaire were administered to a sample of 743 undergraduate students. The incidence of left-handedness was not related to the report of any of the diseases surveyed. Among right-handers, preference scores were slightly lower (less right-handed) in those reporting drug allergies or migraine. These data provide no support for the argument that handedness and immune disorders are related.
Adult↗
Left-handedness, homosexuality, HIV infection and AIDS.
Left-handedness was assessed in a large sample of male homosexuals and male and female heterosexuals, some of whom had been tested for HIV infection, and others of whom had AIDS. No association was found between left-handedness and homosexuality, although there was an excess of left-handers in subjects who had been tested for HIV infection (irrespective of whether the test was negative or positive). This result can be interpreted in three possible ways: as a response bias on the part of left-handers who were aware of the Geschwind hypothesis that left-handedness may confer a vulnerability to AIDS; as due to left-handedness being associated with AIDS infection and the incidence in AIDS patients being artefactually low due to an excess mortality in left-handed AIDS patients; and as left-handers showing both an increased vulnerability of HIV infection and a reduced likelihood of progression of HIV infection into AIDS. Our data are unable to distinguish between these hypotheses. Left-handedness was not associated with any of seventeen specific conditions, including migraine, dyslexia and stuttering.
Acquired Immunodeficiency Syndrome↗
Geschwind's theory of cerebral lateralization: developing a formal, causal model.
Geschwind and Galaburda (1987) have proposed a complex and influential model of cerebral lateralization that is based on the argument that increased fetal testosterone levels modify neural development, immune development, and neural crest development. The theory can explain many aspects of cerebral lateralization and its relation to learning disorders, giftedness, and immune deficits. This article clarifies the structure of the theory by presenting it as a causal-path model. The internal coherence of the model is then evaluated by assessing the central concept of anomalous dominance, the role of timing in the articulation of the model, and the invocation of nonlinear processes. Finally, the article considers the problems implicit in testing a "grand" theoretical model and derives some principles for assessing the testability of various predictions, given the practical constraints of sample size and the problems of measurement error.
Autoimmune Diseases↗
Left-handedness and myasthenia gravis.
In two separate studies comparing the handedness of patients suffering from myasthenia gravis with matched controls, no evidence was found to support the Geschwind Behan hypothesis of an association between autoimmune disease and left-handedness. Counter to prediction both studies found marginally lower incidences of left-handedness in myasthenics, and when combined with the similar result of Cosi et al. (Cortex 24, 573-577, 1988) the difference was highly statistically significant. The personality of myasthenics, as assessed by the Eysenck Personality Questionnaire (EPQ), and in particular the psychoticism scale, which has been postulated to be related to androgen levels, was not significantly different from controls. However, assessment of sex-roles using the Bem Sex Role Inventory suggested that female myasthenics were more masculine than controls.
Adult↗
Revaccination with BCG: its effects on skin tests in Kuwaiti senior school children.
Following a policy of BCG vaccination adopted in Kuwait more than 20 yrs ago, children receive their first vaccination just before starting school. Those who have a response of less than 10 mm induration to 2 tu of RT23 PPD, when they are 13 yrs old, are revaccinated. The effects of this revaccination on skin test positivity in a group of 18 yr old senior school children have been investigated. In a random study group 23% were found to have received BCG a second time. Revaccination resulted in a significant increase in positivity to tuberculin, and to the other 6 reagents tested, that was much more than would have been expected due to the passage of time alone in low responders. Scars of the second BCG vaccination were larger than those after the first vaccination, and showed a sex difference, with scars being significantly larger in boys than in girls. Boys also tended to show the largest responses to skin tests, with the notable exception of tuberculin to which girls showed the largest response. In most cases responses to skin tests were larger after revaccination than after a single vaccination. Based on this study, it is impossible to be sure that revaccination improved protective immunity, but the increase in tuberculin responsiveness, and recognition of environmental mycobacterial species may be indirect evidence supporting this conclusion.
Adolescent↗
A core medical curriculum.
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Clinical Clerkship↗
Prospective study of the disadvantage of people from ethnic minority groups applying to medical schools in the United Kingdom.
To assess whether the ethnic origin of applicants affects their likelihood of being accepted into medical school in the United Kingdom the outcome for the 2399 applicants who applied to read medicine at university in 1986 and included St Mary's Hospital Medical School as one of their five choices was studied prospectively. Altogether 2040 of the 2399 applicants were British (United Kingdom) nationals, constituting 24.7% (n = 8249) of all home applicants for medicine in 1986, and 1971 of them with postal addresses in the United Kingdom were sent questionnaires asking about their ethnic origin, whether English was their first language, and about their attitudes to ethnic monitoring. A total of 1817 (92.2%) applicants returned the questionnaire, 401 (22.6%) saying that they were from an ethnic minority group and 393 (21.6%) having non-European surnames. Multiple logistic regression identified 11 significant predictors of successful application, of which grades at O and A level, application after A levels, and date of application were the most important. After taking these four variables into account the predicted acceptance rates for home students on the basis of their application forms alone were 47.8% for white applicants and 35.6% for applicants from ethnic minority groups compared with actual acceptance rates of 49.6% and 27.3%, respectively. The difference in success of white and non-white applicants could partly but not entirely be explained by differences in the characteristics considered to be important in a professional context by selectors during shortlisting of candidates: academic ability, interests, and contribution to the community. No differences in the success rate of applicants from ethnic minority groups to individual medical schools could be identified. More research is needed to discover how perceptions of professional suitability are assessed from application forms and interviews.
Educational Measurement↗
The concept of disease: its evolution in medical students.
First, third and fifth year medical students were asked to say to what extent they considered each of 38 conditions to be a disease, to be treatable, to be serious, to be the fault of the patient and to be external in cause. Fifth year students were significantly more inclusive in their use of the term disease, applying it to far more conditions, with third year students midway between the first and fifth year students. The use of the term disease did not relate to any great extent with its treatability, seriousness, blame or externality. The concept of disease, despite the difficulty of a consistent, formal philosophical definition, is heuristically useful, and is applied readily by medical students, evolving as students progress through medical school, in a way that cannot be explained in relation to other perceptions of the conditions.
Attitude to Health↗
Short-listing of applicants from UCCA forms: the structure of pre-selection judgements.
Applicants for admission to St Mary's Hospital Medical School in 1986 were short-listed for interview by one of four assessors, who each made their assessments on a nine-item pro forma. One short-lister had also been studied in detail during 1981. Short-listers used the full range of possible judgements, in approximately the proportions requested. Only minor differences were found between them in the mean and range of their judgements, suggesting that similarity of standards can be maintained while using a number of separate short-listers. A confirmatory factor analysis of individual short-listers' judgements showed that all were extracting three separate factors, named 'Academic ability', 'Interests' and 'Contribution to community', although the less experienced short-listers differentiated these items less well than the more experienced. The short-lister assessed in 1981 and 1986 had retained an almost identical factor structure over the 5-year period.
Educational Measurement↗