Biological correlates of high mathematical reasoning ability

An investigation into asymmetrical cortical regulation of salivary S-IgA in conscious man using transcranial magnetic stimulation

Transcranial magnetic stimulation (TMS) can activate discrete areas of the cerebral cortex through the intact skull of healthy conscious volunteers. A magnetic coil generates a brief and focused magnetic field that penetrates the skull to activate the specific area of cerebral cortex beneath. This non-invasive procedure is painless, well tolerated by participants and now widely used to explore brain function. We used TMS to investigate asymmetrical cortical regulatory influences on one aspect of immune function: secretion of the antibody immunoglobulin A (S-IgA) into saliva. The right and left temporo-parietal-occipital cortex of 16 healthy, conscious subjects was stimulated on two different occasions, at least 1 week apart. There was an immediate increase in S-IgA concentration following both right and left stimulation. Saliva volume was reduced immediately post-right but not left stimulation. When secretion (microg/min) of S-IgA was calculated (controlling for changing saliva volume) an increase was apparent following left but not right hemisphere stimulation. Furthermore, a significant difference between the relationship between S-IgA concentration and volume of saliva post-left and right stimulation was observed. We conclude that TMS can be used as a tool to investigate cortical regulation of autonomic and immune function in healthy, conscious human subjects and that secretion of saliva and S-IgA is differentially affected by stimulation of the left and right cerebral cortex.

Myopia, intelligence, and the expanding human neocortex: behavioral influences and evolutionary implications

The first two parts of this monograph document that areas of the human neocortex heavily used to cope with a complex, language-driven society have been expanding rapidly and suggest strongly that this is linked with the huge upsurge that's occurred in myopia, and with the large gradual 20th-century increase in measured intelligence. Part III proposes mechanisms capable of supporting such rapid changes, without violating the basic precepts of Darwin's thinking. Part IV discusses the social and evolutionary ramifications of our apparent proclivity for rapid, progressive, adaptive neocortical change, and suggests areas for productive research.

Relationship between left-handedness and allergic symptomatology

Handedness and health parameters were assessed in 70 infants. Video recordings were employed for handedness analysis. The infants' growth and health were periodically followed up from birth and information was retrieved from medical records. A significant association between left-handedness and allergy score was found (P < .05). Age (P < .02) and sex (P < .01) appear to be significant covariates. It appears that the possible association between left-handedness and immune-based diseases among adults applies to infants as well. A possible biologic marker for allergy should be incorporated in future research.

Is there really a syndrome involving the co-occurrence of neurodevelopmental disorder talent, non-right handedness and immune disorder among children?

This paper is the first large-scale attempt to test Geschwind and Galaburda's (1985a, 1985b, 1985c) hypothesis that there should be a four-way association among neurodevelopmental disorders (NDs), special talents, non-right handedness, and immune disorders. In a sample of 11,578 children, several two-way associations were found, but not those most strongly predicted by the theory. For example, non-right handedness was not associated with NDs considered to be secondary to left hemisphere dysfunction (e.g., articulation disorder, reading disability, verbal aptitude deficits). Instead, non-right handedness was associated with NDs that involve generalized brain damage (e.g. cerebral palsy, mental retardation, and seizures). One immune disorder (asthma) was associated with one ND (attention deficit disorder); immune disorder was not associated with non-right handedness. Less than 1% of this sample manifested the co-occurrence of any three or four of these markers. In sum, there was little evidence in support of the syndrome suggested by Geschwind and Galaburda (1985a, 1985b, 1985c).

Performance on the Wechsler Intelligence Scale for Children as related to salivary testosterone in children with learning disabilities: a poststudy analysis

Reanalysis of testosterone values published in 1993 gave a significantly higher mean and standard deviation for 15 learning-disabled children scoring P > V than those for 10 scoring V > P but not for a matched nonlearning-disabled group. Replication with larger samples would allow a test of hemispheric integration.

Brain lateralization and immunomodulation

The two sides of the brain may be differently involved in the modulation of immune responses as demonstrated by lesional and behavioral approaches in rodents. Lesions of right or left neocortex induced opposite effects on various immune parameters including mitogen-induced lymphoproliferation, interleukin-2 production, macrophage activation or natural killer cell activity. This animal model, useful to elucidate whereby the brain and the immune system can communicate, appears to be suitable for studying the immune perturbations observed during stroke in humans. Brain asymmetry in modulation of immune reactivity may also be demonstrated in intact animal using a behavioral paradigm. The direction of a lateralized motor behavior ie paw preference in a food reaching task, correlated with an asymmetrical brain organization, was shown to be associated with lymphocyte reactivity, natural killer cell activity and auto-antibody production. The association between paw preference and immune reactivity in mice varies according to the immune parameters tested and is a sex-dependent phenomenon in which genetic background may be involved. The experimental models for investigating asymmetrical brain modulation of the immune system should be useful for studying several physiological, pathological and genetic aspects of neuroimmunomodulation.

Association between left-handedness and allergy: a reappraisal

There are conflicting reports in the literature about the possible association between left-handedness and immune disorders, including autoimmune diseases as well as allergies. In this study we compared the distribution of right- and left-handers, assessed with the Edinburgh Handedness Inventory, in a group of patients consulting an allergy clinic and a control population with a similar sex and age distribution. There was no overall association between left-handedness and allergies, although we found a tendency towards left-handedness in patients whose allergic symptoms started before puberty, suggesting that left-handers may have an increased predisposition to allergic disease that manifests itself during early life.

Myopia and intelligence: a pleiotropic relationship?

The well-established association between myopia and superior intelligence in the general population was investigated in a group of intellectually gifted children and their less gifted full siblings to determine whether the relationship of myopia to psychometric intelligence is consistent with the hypothesis of pleiotropy, i.e., both characteristics are affected by the same gene or set of genes. Failure to find a difference in degree of myopia, assessed as a metric variable, between intellectually gifted and nongifted siblings would contradict pleiotropy. A variety of possible causal pathways, both genetic and environmental, have been hypothesized in the literature to explain the relationship between intelligence and myopia, and these still cannot be ruled out. It is theoretically noteworthy, however, in view of the independent evidence for the considerable heritability of both intelligence and myopia, that the highly significant gifted-nongifted sibling difference in myopia found in the present study is consistent with the hypothesis that intelligence and myopia are related pleiotropically.