Differences In Brain Organization Research Articles

Maturation of the coherence of EEG activity in normal and learning-disabled children

The age effect on coherence has been studied in control (98) and learning-disabled (LD, 54) school-aged children (from 6.0 to 16.8 years old). The EEG recordings were made at rest in 15 leads, and 105 pairwise combinations for coherence were calculated (each lead was compared with all the rest) for delta, theta, alpha, beta and total frequency bands. A significant increase of coherence with age was found in both groups, witha different pattern of maturation. In the control group, a significant increase with age was found in the coherences between posterior regions and vertex (Cz). A significant decrease with age in the coherence between frontal areas was observed, especially in the theta band. The LD group showed a different pattern: no significant relation with age was found in the coherence between any lead and vertex. A high effect of age on coherence between temporal regions was observed with a predominance of the left side in comparison with the contralateral and the ipsilateral. No decrease in frontal coherence was found: in the same region where the control group showed negative values with age, the LD groups had no age effect. The results obtained are discussed as differences in brain organization, in myelogenesis and synaptogenesis and an explanation of the etiology of LD is proposed.

Hemisphere size asymmetry predicts relative verbal and nonverbal intelligence differently in the sexes: An MRI study of structure—Function relations

Hemispheric size asymmetry differences as assessed from MRIs of 39 healthy college students were correlated with prorated WAIS-R Verbal IQ minus Performance IQ and Vocabulary minus Block Design scores within subjects. In men, a relatively larger left hemisphere predicted better verbal than nonverbal ability, whereas in women a larger left hemisphere predicted relatively better nonverbal than verbal ability. The results were interpreted as providing evidence for sex differences in brain organization.

Sex, handedness, mathematical ability, and biological causation.

An important part of Benbow's (1988) assertion that sex differences in mathematical ability are primarily due to biological factors is the link between a trait that is assumed to reflect differences in brain organization (left-handedness) and mathematical giftedness. It is shown that the link between mathematical giftedness and an increased prevalence of left-handedness is not convincing. However, Benbow's (1986) data do show a convincing link between strong right-handedness and the lack of mathematical giftedness, in agreement with Annett and Manning's (1990a, 1990b) recent work.

EEG spectra in severely dyslexic men: rest and word and design recognition

To identify and localize differences in brain functioning, electrical activity was recorded with a full complement of scalp electrodes in 14 healthy, severely dyslexic men (mean age = 22 years, S.D. = 3) and 15 matched controls during rest and during word and design recognition. The electroencephalograms were spectrum analyzed, and the mean amplitude in each of 5 bands — delta, theta, alpha, slow beta and fast beta — compared topographically between conditions and groups. The two tasks did not elicit differentially lateralized patterns of electrical activity, but produced anteroposterior differences in alpha and theta. The Designs tasks, more difficult for both groups, was associated with less posterior alpha than was the Words task. The strongest group difference was likewise seen along an anteroposterior axis on the Designs task. With performance equal to that of controls, the dyslexics showed relatively greater fronto-central theta and less posterior theta (a more activated state), suggesting that dyslexics were compensating for less efficient information processing. There were no group differences in overall amplitude in any band for any condition. The differences in the topographical distribution of theta may reflect subtle differences in brain organization or compensatory recruitment of widely distributed neuronal networks.

Cerebral hemisphere asymmetry and individual differences in cognition

The present article examines the potential connection between hemispheric asymmetry and individual differences in cognition. Lateral differences in left- and right-hemisphere function are clearly manifest in humans and imply that differences in brain organization may be accompanied by behavioral and/or intellectual consequences. The authors identify several hemispheric dimensions on which individuals may differ (i.e., degree of dominance, direction of dominance, characteristic arousal level, complementarity of functioning), and investigate the possibility that underlying patterns of cerebral hemisphere asymmetry may be related to differences in cognitive abilities as reported for males and females, left- and right-handers, intellectually precocious and dyslexic individuals. The conclusion is made that a connection between hemispheric asymmetry and individual differences in cognition is tenable, but that further research is required before any definitive cause and effect relationships can be drawn.

Evidence for sex differences in brain organization in recovery in aphasia

Ninety-one adult aphasics of both sexes were studied before and after a 3-month period of language therapy. Although no initial sex difference was found in severity of language disorders, females within the global aphasic group showed significantly greater improvement in three tests of language comprehension. It is suggested that more bilateral representation of language functions in the female brain may account for this greater improvement.

Sex differences in brain organization: implications for human communication.

This article reviews current knowledge in two major research domains: sex differences in neuropsychophysiology, and in human communication. An attempt was made to integrate knowledge from several areas of brain research with human communication and to clarify how such a cooperative effort may be beneficial to both fields of study. By combining findings from the area of brain research, a communication paradigm was developed which contends that brain-related sex differences may reside largely in the area of communication of emotion.

The Influence of Sex and Age on Unilateral Cerebral Lesion Sequelae

Group differences in unilateral lesion sequolae may suggest group differences in brain organization, but only if the two groups have equivalent lesions. In an analysis of sex and age on neuropsychological performance, we quantified lesion size and location, based on CT images. Significant sex by group (left, right, controls) interactions were found for variables most related to left hemisphere functions (verbal intellectual, right motor, right sensory), but not for variables most related to right hemisphere functions (nonverbal intellectual, left motor, left sensory). For each interaction, left males performed worse than left females, but right males were better than right females. Further, these sex differences were not due to sex differences in lesion parameters. Age was not a major determinant of lesion sequelae.

Interhemispheric coupling coefficients: sex differences in brain neurochemistry.

Previously it was shown that the presence of a significant positive correlation between measures of the right and left hemispheres may be taken as evidence of a negative feedback loop linking the hemispheres [Denenberg, V. H. Am. J. Physiol. 238 (Regulatory Integrative Comp. Physiol. 7): R3-R13, 1980]. Such a finding is indicative of a different form of brain organization, compared with brains that lack this correlation. The purpose of this paper was to compare male and female rats with respect to correlations of left- and right-sided values for a set of brain neurochemicals. The variable of sex was chosen because there are ample data showing differences in brain organization. Neurochemical correlations in the nucleus accumbens and the striatum did not demonstrate any sex difference, but differences were found in neocortex: female rats had significantly greater hemispheric correlations than males for dopamine, 5-hydroxyindoleacetic acid, and serotonin turnover.

Sex differences in brain organization: different brains or different strategies?

Sex differences in brain organization: different brains or different strategies?

Sex differences in brain organization

Sex differences in brain organization

Sex Differences in Cognitive Functioning: Evidence, Determinants, Implications

The purpose of this article is to examine the evidence for sex differences in cognitive functioning and to review and evaluate evidence for hormonal, genetic, neuro-anatomical, and cultural determinants of such differences. Inadequacies in the evidence for sex differences, such as underreporting of negative findings, failure to measure effect size, small sample sizes, etc., are noted. It is likely that sex hormones influence the organization and functioning of the brain. Sex differences in brain organization and functioning are discussed. In summary, the existence of sex differences in cognitive functioning is clear, but further research is needed to elucidate the determinants of these differences.

Some problems and paradoxes associated with recent accounts of hemispheric specialization

Recent studies of lateralization of function are critically reviewed. Particular attention is paid to claims of topological differences in brain-organization between left- and right-handers, and males and females. It is concluded that these, sometimes incompatible claims, cannot be fully evaluated until more is known about (a) the psychological structure of various linguistic and visuospatial tasks; (b) the nature of individual differences in approach to such tasks.