Lateralization In Males Research Articles

Gender differences in the functional language networks at birth: a resting-state fNIRS study.

Numerous studies reported inconsistent results concerning gender influences on the functional organization of the brain for language in children and adults. However, data for the gender differences in the functional language networks at birth are sparse. Therefore, we investigated gender differences in resting-state functional connectivity in the language-related brain regions in newborns using functional near-infrared spectroscopy. The results revealed that female newborns demonstrated significantly stronger functional connectivities between the superior temporal gyri and middle temporal gyri, the superior temporal gyri and the Broca's area in the right hemisphere, as well as between the right superior temporal gyri and left Broca's area. Nevertheless, statistical analysis failed to reveal functional lateralization of the language-related brain areas in resting state in both groups. Together, these results suggest that the onset of language system might start earlier in females, because stronger functional connectivities in the right brain in female neonates were probably shaped by the processing of prosodic information, which mainly constitutes newborns' first experiences of speech in the womb. More exposure to segmental information after birth may lead to strengthened functional connectivities in the language system in both groups, resulting in a stronger leftward lateralization in males and a more balanced or leftward dominance in females.

Reduced Microstructural Lateralization in Males with Chronic Schizophrenia: A Diffusional Kurtosis Imaging Study.

Decreased brain lateralization is considered a trait marker of schizophrenia. Whereas reductions in both functional and macrostructural gray matter laterality in schizophrenia are well established, the investigation of gray matter microstructural lateralization has so far been limited to a small number of ex vivo studies, which limits the understanding of neurobiological substrates involved and development of adequate treatments. The aim of the current study was to assess in vivo gray matter microstructure lateralization patterns in schizophrenia by employing the diffusion kurtosis imaging (DKI)-derived mean kurtosis (MK) metric. MK was calculated for 18 right-handed males with chronic schizophrenia and 19 age-matched healthy control participants in 46 bilateral gray matter regions of interest (ROI). Microstructural laterality indexes (μLIs) were calculated for each subject and ROI, and group comparisons were conducted across regions. The relationship between μLI values and performance on the Wisconsin Card Sorting Test (WCST) was also evaluated. We found that compared with healthy controls, males with chronic schizophrenia had significantly decreased μLI across cortical and subcortical gray matter regions, which was correlated with poorer performance on the WCST. Our results suggest the ability of DKI-derived MK to capture gray matter microstructural lateralization pathology in vivo.

Pupil-size asymmetry is a physiologic trait related to gender, attentional function, and personality

ABSTRACTA small difference in the size of the two pupils is common in healthy individuals, a condition termed benign or physiologic anisocoria (BA). Past research indicates that BA is probably caused by asymmetry in sympathetic nervous system (SNS) function [e.g., Rosenberg (2008). Physiologic anisocoria: A manifestation of a physiologic sympathetic asymmetry. Neuro-Ophthalmology, 32, 147–149]. This study is the first to show that BA varies with psychological factors linked to brain asymmetry and autonomic arousal, including gender, attention, and personality. Males exhibited a more directional BA than females, consistent with greater hemispheric lateralization in males. BA also varied with a self-report measure of attentional function, consistent with evidence of hemispheric asymmetry in visuospatial attention networks. Finally, BA varied with personality traits linked to autonomic arousal. Individuals exhibiting higher Meanness and Boldness, and lower Empathy scores tended to show more directional BA. This link between personality traits and BA may be related to brain asymmetries in autonomic arousal and emotion-related processing. If future studies employing direct measures of lateralized brain activity confirm the link between BA and SNS asymmetries, this new metric may prove useful in discovering new relationships between brain organization and psychological function, and how these relationships vary across individuals.

The development of hand preference and dichotic language lateralization in males and females with congenital adrenal hyperplasia

ABSTRACTPeople with congenital adrenal hyperplasia (CAH) are exposed to elevated levels of androgens in utero due to overproduction by the adrenal cortex. In order to test whether high levels of prenatal androgens influence the development of handedness preferences and left-hemisphere language representation, we studied 39 patients with CAH (28 females, 11 males) and 25 unaffected sibling controls (17 females, 8 males). Hand preference for 15 unimanual activities was evaluated via questionnaire and pantomime, and a consonant–vowel dichotic listening test was administered. Contemporary theories disagree as to whether high testosterone is said to increase or decrease the probability of developing a typical right-hand preference. Results showed no significant differences on the handedness inventory. Relative to controls, however, patients with CAH showed a significantly larger right-ear advantage on the dichotic syllables task, indicating stronger left-hemisphere lateralization of language. These results support an emerging body of evidence suggesting that high testosterone may bias lateralized development toward the population norm, but run counter to the Geschwind–Behan–Galaburda model which associates high prenatal testosterone with a greater prevalence of left-handedness.

MRI volumetry of the temporal lobe in Sudan: Validated protocol and preliminary normative data

MRI volumetry of the temporal lobe in Sudan: Validated protocol and preliminary normative data

Sex differences in cognitive control are associated with midcingulate and callosal morphology

Sex differences in the processing of cognitively demanding tasks have attracted much attention in recent years. While there seems to be some agreement on differences between males and females concerning spatial abilities and language skills, a consensus regarding executive functions or cognitive control has not been reached yet. In the present study, male and female subjects participated in a lateralized, tactile Stop-Signal task. Although the behavioral data did not show any differences between sexes, event-related potentials pointed to varieties in neurocognitive processing. As inferred from N200 amplitudes, differences between left- and right-hand stimulation suggested a strong degree of functional lateralization in males in accordance with a left-hemispheric dominance. Females, on the other hand, rather seemed to exhibit a functionally symmetric organization of relevant processes. The P300 did also show evidence of sex-related differences, reflecting disparities in the degree or quality of interhemispheric interaction. In addition, behavioral and electrophysiological parameters were correlated with individual metrics concerning the degree of midcingulate folding asymmetry and the morphology of the corpus callosum. Differential associations of these morphological characteristics with the N200 and P300, respectively, underscore the notion of relevant structure-function associations of the midcingulate cortex and the N200 on the one hand, and the corpus callosum and the P300 on the other hand. Obviously, these variations in neuroanatomy contribute to the observed behavioral and electrophysiological differences between women and men.

Interhemispheric communication in schizophrenia

The corpus callosum (CC) is the brain's largest white matter tract, mostly composed by both myelinated and unmyelinated fibres, connecting the two cerebral hemispheres. The CC can be divided into different sections: rostrum, genu, body, isthmus and splenium (Aboitiz et al., 1992). Myelinated fibres predominate in the midbody and the splenium while unmyelinated fibres are more numerous in the rostrum and the genu. The callosal fiber disposition approximately reflects brain topography: the anterior sections connect the frontal lobes, the median sections connect temporal and parietal regions, and the posterior sections link occipital areas (Pandya et al., 1971). This traditional picture, however, which has been obtained mainly through studies in non-human primates has been partly modified by modern diffusion tensor imaging studies in humans (Hofer & Frahm, 2006). The CC matures after birth through adolescence and into early adulthood and is involved in different cognitive processes such as sensory-motor integration, attention, language, arousal and memory. Its size has been shown to be associated with handedness, sex (i.e., greater splenium in females and greater genu in males, Dubb et al., 2003) and cerebral laterality (i.e., inverse correlation between callosal connectivity and brain lateralization in males; Luders et al., 2003), and age (Ota et al., 2006) Specifically, age-related callosal degeneration has been detected by a diffusion tensor imaging (DTI) study (Ota et al., 2006) in the sub-regions that connect areas which are thought to be vulnerable to normal aging: the genu, rostral body, and isthmus. This result replicated post mortem findings of callosal degeneration in rostral body, anterior midbody and isthmus (Aboitiz et al., 1996).

Priming vs. rhyming: Orthographic and phonological representations in the left and right hemispheres

The right cerebral hemisphere has long been argued to lack phonological processing capacity. Recently, however, a sex difference in the cortical representation of phonology has been proposed, suggesting discrete left hemisphere lateralization in males and more distributed, bilateral representation of function in females. To evaluate this hypothesis and shed light on sex differences in the phonological processing capabilities of the left and right hemispheres, we conducted two experiments. Experiment 1 assessed phonological activation implicitly (masked homophone priming), testing 52 (M = 25, F = 27; mean age 19.23 years, SD 1.64 years) strongly right-handed participants. Experiment 2 subsequently assessed the explicit recruitment of phonology (rhyme judgement), testing 50 (M = 25, F = 25; mean age 19.67 years, SD 2.05 years) strongly right-handed participants. In both experiments the orthographic overlap between stimulus pairs was strictly controlled using DICE [Brew, C., & McKelvie, D. (1996). Word-pair extraction for lexicography. In K. Oflazer & H. Somers (Eds.), Proceedings of the second international conference on new methods in language processing (pp. 45–55). Ankara: VCH], such that pairs shared (a) high orthographic and phonological similarity (e.g., not–KNOT); (b) high orthographic and low phonological similarity (e.g., pint–HINT); (c) low orthographic and high phonological similarity (e.g., use–EWES); or (d) low orthographic and low phonological similarity (e.g., kind–DONE). As anticipated, high orthographic similarity facilitated both left and right hemisphere performance, whereas the left hemisphere showed greater facility when phonological similarity was high. This difference in hemispheric processing of phonological representations was especially pronounced in males, whereas female performance was far less sensitive to visual field of presentation across both implicit and explicit phonological tasks. As such, the findings offer behavioural evidence indicating that though both hemispheres are capable of orthographic analysis, phonological processing is discretely lateralised to the left hemisphere in males, but available in both the left and right hemisphere in females.

Sex Differences, Gamma Activity and Schizophrenia

This study explores the possibility that the more favourable clinical prognosis in females with schizophrenia may be associated with their greater network interconnectedness, which is possibly reflected in enhanced “Gamma” (40 Hz) electrical brain activity. An auditory “oddball” task was administered to 35 patients with schizophrenia and 35 age and sex matched controls (25 males and 10 females). Peak Gamma amplitude (from a time series of Gamma activity averaged for 40 target stimuli, as well as the immediately preceding 40 background tones) was examined across 19 sites. Peak Gamma activity occurred 250 to 450 ms in targets and 350 to 550 ms in backgrounds. Multiple within and between group MANOVAs were undertaken analysing both Peak Gamma amplitude (microvolts) and latency (milliseconds). Within-group, the control males showed a pattern of earlier Gamma latency in the right compared with the left hemisphere (F(1, 33) = 3.70, p <. 06), while control females exhibited delayed latency frontally compared with the posterior region (F(1, 33) = 6.25, p <. 04). This male lateralization finding and the anterior/posterior gradient in females is consistent with Goldberg's model. The patient group however, failed to show this male lateralized and female frontal-posterior pattern of Gamma activity, suggesting suboptimal network integration in the patient group, in both males and females.

MEG based brain laterality: Sex differences in normal adults

Magnetoencephalographic (MEG) auditory evoked fields produced by short tone pips were recorded from 34 normal adults (17 males, 17 females) and the 100 msec latency component (M100) localized in left and right hemispheres. Absolute M100 location in the antero-posterior dimension was calculated for each subject. M100 sources were significantly further anterior in the right hemisphere of males. Magnetic resonance (MR) based anatomy of the superior temporal gyri (STG) in a subset of 17 subjects showed that in the left STG of both males and females M100 sources were located approximately midway on the STG. In the right hemisphere of males, however, M100 sources were significantly further anterior on the STG than was the case for females. The findings are compatible with a sex based difference in right STG functional anatomy, with evidence of greater hemispheric lateralization in males compared to females based upon a predominantly right hemisphere contribution.

Sex-related asymmetries in the morphology of the left and right hippocampi? A follow-up study on epileptic patients.

Cell densities were determined in left and right surgically removed hippocampal tissue of epileptic patients. Pyramidal cells were studied in CA1, CA4, and the dentate gyrus. Lower densities of nucleolated cells were found for males in the right CA1 and CA4 than on the left while there was no significant left-right difference in females. Moreover, we found a probable sex difference in intercorrelations of nucleolated cells among the three subfields. In males, they were positive and significant on the left while they were low on the right. In females, positive significant intercorrelations were obtained between some subfields and not between other subfields, on either side. The present findings suggest greater hippocampal lateralization in males than in females with higher hippocampal neuronal connectivity on the left in males than on the right.

Quantitative analysis of gender differences in the effects of lateralized lesions on verbal and performance IQ

Previous studies and meta-analyses have demonstrated that males have larger differences between Verbal IQ (VIQ) and Performance IQ (PIQ) following unilateral brain lesions. Several theories have been proposed as an explanation of this finding, including a greater degree of functional lateralization in males, gender differences in the organization of language centers within the left hemisphere, and differences in problem-solving strategy for PIQ. We apply quantitative methods for analysis of relations between lesion location and behavior to a sample of 64 males and females with unilateral brain lesions. Statistical test conducted in LISREL-VII suggest that in females, a single model can describe the relationships between lesion location and VIQ and PIQ, with left-hemisphere lesions producing more severe deficits on both measures. In males, separate models of the relationships between lesion location and VIQ and PIQ are required.

Semantic capabilities of the left and right cerebral hemispheres in categorization tasks: Effects of verbal-pictorial presentation

Two lateral tachistoscopic experiments were carried out to test semantic capabilities of the left and right cerebral hemispheres through categorization tasks with verbal and pictorial presentations. RVF advantages were obtained for verbal presentations in both category-membership and category-matching tasks. However, no significant visual-field differences were found for any pictorial presentation. We also found a higher degree of sensitiveness of the positive judgements for the detection of hemispheric differences and sex differences in patterns of functional asymmetries with a greater lateralization in males.

The influence of sex and handedness on the development of lateralization of speech processing

Sex has been shown to affect lateralization of speech in adults. However, there has been no convincing evidence that sex exerts any influence on speech lateralization in children. The present experiment was conducted to determine the age at which sex influences speech processing. Younger and older right-handed and left-handed children participated in a verbal auditory task. The results of this experiment demonstrate that there are sex-related changes in lateralization of linguistic processing with age. Boys and girls both show left-hemisphere specialization for speech in early childhood. However, by late childhood the adult pattern of greater language lateralization in males than in females is established.

The influence of sex on the development of lateralization of speech

Younger and older right-and left-handed children participated in verbal and nonverbal auditory tasks. The results of these experiments demonstrate that there are sex-related changes in lateralization of linguistic processing with age. Boys and girls both show left-hemisphere specialization for speech in early childhood. However, by late childhood the adult pattern of greater language lateralization in males than in females is established.

Sex And Visual Field Effects on Accuracy and Decision Making When Subjects Classify Male and Female Faces

Male and female subjects classified tachistoscopically presented slide photographs of faces as male or female. In Experiments I and II presentation was at random to the right or left visual hemifield. Two different signal detection procedures demonstrated that accuracy for both visual fields is equivalent in females and that males show a marked right-field advantage. A third experiment showed that this field advantage is preserved for males when presentation right or left is by blocks of trials suggesting that the left hemisphere is specialized for classification tasks. Results also showed that optimization in signal detection tasks may be lateralized for both males and females though males optimize more poorly than females in the left visual field. The data are taken to demonstrate equipotentiality of hemispheric functioning in females and stronger hemispheric lateralization in males.