Sex differences in cerebral laterality of language and visuospatial processing

Sex differences on language and visuospatial tasks are of great interest, with differences in hemispheric laterality hypothesized to exist between males and females. Some functional imaging studies examining sex differences have shown that males are more left lateralized on language tasks and females are more right lateralized on visuospatial tasks; however, findings are inconsistent. Here we used functional magnetic resonance imaging to study thirty participants, matched on task performance, during phonological and visuospatial tasks. For each task, region-of-interest analyses were used to test differences in cerebral laterality. Results indicate that lateralization differences exist, with males more left lateralized during the phonological task and showing greater bilateral activity during the visuospatial task, whereas females showed greater bilateral activity during the phonological task and were more right lateralized during the visuospatial task. Our data provide clear evidence for differences in laterality between males and females when processing language versus visuospatial information.     

DEVELOPMENTAL SEX DIFFERENCES IN THE RELATION OF NEUROANATOMICAL CONNECTIVITY TO INTELLIGENCE

Recent neuroimaging research has shown sex-related differences in the relationship between brain structure and cognitive function. Anatomical studies have shown a greater reliance for cognitive function on white matter structure in adult females, and a greater reliance on gray matter structure in adult males. Functional neuroimaging studies have also shown a greater correlation between brain connectivity and cognitive function in females. However, this relationship is not present in young childhood (5 years old) but appears during the developmental period. Here sex differences in structure–function relationships and their developmental trajectory are investigated using diffusion tensor imaging (DTI) on a large cohort of over 100 normal children ages 5–18. Significant sex–X–IQ interactions on fractional anisotropy (FA), a marker for white matter organization, were seen in the left frontal lobe, in fronto-parietal areas bilaterally, and in the arcuate fasciculus bilaterally, with girls showing positive correlations of FA with IQ, and boys showing a negative correlation. Significant sex–X–IQ–X–age interactions on FA were also seen in the left frontal lobe and in fronto-parietal areas bilaterally, showing a developmental effect. These results strongly corroborate previous findings regarding sex differences in structure–function relationships regarding intelligence. Results also indicate that a naïve interpretation of “more is better” with respect to FA may not be accurate, especially in adult males.     

Intelligence and neural efficiency: The influence of task content and sex on the brain–IQ relationship

In studying physiological correlates of human intelligence, new brain imaging techniques like positron emission tomography (PET) and electroencephalography (EEG) mapping methods focus on the level and topographical distribution of cortical activation. Actually, there is strong empirical evidence that more intelligent individuals display a more focused cortical activation during cognitive performance resulting in lower total brain activation than in less intelligent individuals (i.e., neural efficiency hypothesis). Former studies have used only single, homogeneous tasks and most of the studies have been performed using males. Therefore, here the influence of different task content and of sex on the relationship between intelligence and cortical activation has been tested. In a sample of 26 males and 25 females, we administered verbal, numerical, and figural versions of a well-known elementary cognitive task, the so-called Posner task. Our results suggest a comparatively low cortical activation in brighter as compared to less intelligent individuals but this expected neural efficiency pattern interacted with sex and task content: In the verbal Posner task, the females were more likely to produce cortical activation patterns in line with the neural efficiency hypothesis, whereas in the figural task, primarily the males displayed the expected inverse relationship between IQ and cortical activation.     

Enlargement of Neuronal Somata in the LMAN Coincides with the Onset of Sensorimotor Learning for Song

The lateral magnocellular nucleus of the anterior neostriatum (LMAN) in the zebra finch (Taeniopygia guttata) has been shown to play a developmentally restricted role that is essential during song-learning processes. Dendritic spine frequencies and synapse numbers in LMAN have been reported to decline in males during early vocal motor learning and thereafter, but not in females, who do not sing. Nissl staining has shown the LMAN volume to be very similar in both sexes, however. To gain more insight into the development of sex-specific differences in LMAN, the size of neuronal somata and cell nuclei were analyzed in 1-μm semithin sections. Cell somata and nuclei were similar in males and females during the initial phases of sensory memory formation for song, but during early vocal motor learning cell size increased in males and decreased in females. Sex differences in neuronal somata size were present at 50 days and remained throughout life. This sex difference may be indicative of a difference in protein biosynthesis in LMAN, arising as a consequence of vocal learning in males.     

Sex-related developmental differences in the lateralized activation of the prefrontal cortex and amygdala during perception of facial affect

The lateralization of cognitive abilities is influenced by a number of factors, including handedness, sex, and developmental maturation. To date, a small number of studies have examined sex differences in the lateralization of cognitive and affective functions, and in only few of these have the developmental trajectories of these lateralized differences been mapped from childhood through early adulthood. In the present study, a cross-sectional design was used with healthy children (n=7), adolescents (n= 12), and adults (n= 10) who underwent functional magnetic resonance imaging (fMRI) during a task that required perceiving fearful faces. Males and females differed in the asymmetry of activation of the amygdala and prefrontal cortex across the three age groups. For males, activation within the dorsolateral prefrontal cortex was bilateral in children, right lateralized in adolescents, and bilateral in adults, whereas females showed a monotonic relationship with age, with older females showing more bilateral activation than younger ones. In contrast, amygdala activation was similar for both sexes, with bilateral activation in children, right-lateralized activation in adolescents, and bilateral activation in adults. These results suggest that males and females show different patterns of lateralized cortical and subcortical brain activation across the period of development from childhood through early adulthood.     

Transient sex differences during adolescence on auditory perceptual tasks

Many perceptual abilities differ between the sexes. Because these sex differences have been documented almost exclusively in adults, they have been attributed to sex‐specific neural circuitry that emerges during development and is maintained in the mature perceptual system. To investigate whether behavioral sex differences in perception can also have other origins, we compared performance between males and females ranging in age from 8 to 30 years on auditory temporal‐interval discrimination and tone‐in‐noise detection tasks on which there are no sex differences in adults. If sex differences in perception arise only from the establishment and subsequent maintenance of sex‐specific neural circuitry, there should be no sex differences during development on these tasks. In contrast, sex differences emerged in adolescence but resolved by adulthood on two of the six conditions, with signs of a similar pattern on a third condition. In each case, males reached mature performance earlier than females, resulting in a sex difference in the interim. These results suggest that sex differences in perception may arise from differences in the maturational timing of common circuitry used by both sexes. They also imply that sex differences in perceptual abilities may be more prevalent than previously thought based on adult data alone.     

Sex differences in chronic stress effects on memory in rats

Recent studies in rodent models and in humans have shown that the status of both the gonadal and adrenal axes (hypothalamic-pituitary-gonadal, HPG and hypothalamic-pituitary-adrenal, HPA, respectively) can influence learning and memory function. In this article, the effects of activating the HPA axis (stress) on performance of memory tasks in rats are reviewed. More importantly, results are presented which show that chronic stress has a different impact on performance of these tasks depending upon the sex of the rat. These observations are novel and potentially important since few studies, animal or human, have utilized females as subjects in studies of the stress response. Sex differences in the effects of chronic stress on memory were investigated in rats using an object recognition task and two spatial memory tasks, radial arm maze and object location. Given the same chronic stress--21 days of restraint for 6 h each day--males were impaired in all of the memory tests while females showed enhanced performance of the spatial memory tasks and no changes in object recognition performance. Levels of neurotransmitters and metabolites were measured in brain areas important for cognition in the subjects in order to determine neural systems that may respond to stress and mediate the cognitive responses. These results show that responses of monoamine and amino acid containing neural systems may contribute to or underlie sex differences in stress effects on cognition. Stress decreased dopaminergic activity in the frontal cortex and amygdala of males but not females; whereas, in CA3 of the hippocampus, stress increased levels of 5-HT and norepinephrine in females, but not males, and increased GABA in males, but not females. Finally, a possible role for estradiol in mediating sexually differentiated responses to stress was examined. Behavioral and neurochemical evaluations in ovariectomized, stressed females, with or without estrogen replacement, suggest that sex differences in response to stress are influenced by both the organizing and activating effects of estradiol. A few, recent studies in humans, that show sexually dimorphic relationships between chronic stress and cognition, are also highlighted. These results in humans are consistent with the pattern of results in rats. Clearly, further studies are necessary to substantiate sex differences in stress effects on memory function in humans and to understand mechanisms whereby estrogen may influence the stress response in rats. Nonetheless, recent studies show sexually differentiated cognitive responses to chronic stress and underline the importance of considering the sex/gender of subjects when studying the stress response.     

Resolving contradictory findings on sex and social class differences in children's responses to reinforcement

Contradictory results have been reported on the effectiveness of various reinforcers with children of different ages and socioeconomic classes. The present study considered the relative effectiveness of two types of verbal and one type of tangible reinforcement on a two-choice discrimination task (marble-in-the-hole) for preschool children. IQ and operant level were treated as covariates and accounted for the observed differences in performance between the 24 middle-class and 24 lower-class children and between the 24 males and 24 females. Disparate findings of previous studies regarding sex and social class differences might have been reconciled if baseline and IQ had been considered.     

Baby babbling at five months linked to sex hormone levels in early infancy

Gender-dependent differentiation of the brain at morphological, neurochemical and functional levels of organization have been shown to be primarily controlled by sex differences in gonadal hormone concentrations during pre- and early postnatal development. Indeed, previous studies have reported that pre- and perinatal hormonal environments influence brain development and, consequently, affect sex specific long-term language outcomes.Herein, we investigated whether postnatal surges of estrogen (estradiol) and androgen (testosterone) may predict properties of pre-speech babbling at five months. This study is the first attempt to investigate a possible correlation between sex hormones and infants’ articulatory skills during the typical postnatal period of extended hormonal activity known as ‘mini-puberty.’ A hierarchical, multiple regression approach revealed a significant, robust positive relationship between 4-week concentrations of estradiol and individual articulatory skills. In contrast, testosterone concentrations at five months negatively correlated with articulatory skills at the same age in both boys and girls. Our findings reinforce the assumption of the importance of sex hormones for auditory–vocal development towards language in human infants.     

Identifying and explaining apparent universal sex differences in cognition and behavior

With growing recognition that there are universal sex differences in cognition and behavior, four theories have been proposed to account for these differences: the founder effect theory, the social structuralist theory, the evolutionary theory, and the evolutionary neuroandrogenic (ENA) theory. The latter of these theories is described in considerable detail as offering an explanation for most of 65 recently identified apparent universal sex differences (AUSDs) in cognition and behavior. Regarding “ultimate causes” (why), ENA theory asserts that (a) evolutionary-genetic factors incline females to bias their mate choices toward males who are loyal and competent provisioners of resources and (b) males are merely a genetic variant on the female sex selected for responding to female mating biases. In terms of “proximate causes” (how), the theory maintains that high exposure to androgens has evolved to alter the male brain functioning in two specific ways relative to most female brains: (a) suboptimal arousal and (b) a rightward shift in neocortical functioning. These two functional patterns are described and hypothesized to incline males and females to learn differently in many respects. The most fundamental differences involve males learning ways of either complying with or circumventing female mate preferences. Numerous universal sex differences in cognition and behavior are hypothesized to result from these evolved neurohormonal factors, including most of the 65 AUSDs herein summarized in seven categorical tables.     

Adolescent Sex Differences in Response to a Mindfulness Intervention: A Call for Research

Research on mindfulness interventions with adolescents has burgeoned over the last ten years, and findings have demonstrated increases in overall emotional wellbeing post-intervention. However, little is known about the sex differences in response to mindfulness interventions in this age group. In the present study we examine sex differences in outcomes of physiological stress markers during the Trier Social Stress Test (TSST) and emotional wellbeing measures before and after a mindfulness intervention (N?=?15) with 10 female and 5 male adolescents. Additionally, we examine sex differences in course engagement and post-intervention use of mindfulness skills during the TSST. Overall, we found some evidence that females were more engaged than males in the class and also reported less stress post-intervention. We conclude by strongly encouraging future research in this area to more clearly elucidate the different ways in which adolescent males and females engage and respond to mindfulness interventions.     

Sex differences in reactions to outperforming same‐sex friends

The current studies were designed to examine whether female adolescents have more negative reactions than male adolescents to achieving more than their same‐sex friends. In Study 1, 51 females and 48 males from grades 8 and 10 were administered questions assessing their reactions to performing better than their closest same‐sex friends in four domains. Across domains, females reported more negative reactions than males. Further, compared with males, female participants believed that their same‐sex friends would have more negative reactions if they performed better than their friends. In Study 2, 48 females and 49 males age 18 years were asked how they felt about performing better than and equal to their closest same‐sex friends in the domains of romance and academics in both hypothetical and actual situations. Females reported feeling more positive when they received the same outcomes as opposed to better outcomes than their friends. Males did not differ in the valence of their responses to the two outcomes. The implications for sex differences in achievement and friendship are discussed.     

Assessment of male and female behaviour in the employment interview

Personality assessment has a great impact on the outcomes of the selection interview. Women are perceived to have personality characteristics which are different from men. It is doubtful whether these sex stereotyped personality characteristics are based on real differences in verbal and nonverbal behaviour between men and women. Previous studies have shown the influence of sex stereotypes on interview-outcomes. In this study, the relationship between verbal and nonverbal behaviour of male and female applicants and their personality assessment has been investigated. Results show that males and females are assessed stereotypically based on their sex, but also based on their behaviour. For females, a feminine or masculine assessment is of special importance for her chance of selection. The less feminine is a woman's assessment the more likely she is to be accepted as an eligible candidate by the selection board. These accepted women show ‘female’ behaviour as well as ‘male’ behaviour.     

Sex-dependent changes induced by prenatal stress in cortical and hippocampal morphology and behaviour in rats: an update

Recent prospective studies have shown that gestational stress in humans is more likely to cause cognitive and emotional problems in the offspring if it occurs during weeks 12-20 of pregnancy. There are also suggestions that such problems may be gender dependent. This review describes recent studies that found sex differences in the behaviour and brain morphology of rats stressed prenatally during the equivalent period of neuronal development in humans. Learning deficits are more prevalent in males and anxious behaviour in females but their appearance depends also on the timing and intensity of the stress and the age when the offspring were tested. Cognitive deficits and anxiety are linked to a sex-dependent reduction in neurogenesis and in measures of dendritic morphology in the prefrontal cortex and hippocampal formation. Maternal adrenalectomy prior to the stress prevents the anxiety in both sexes and learning deficits in males. Corticosterone administration to the dam to mimic levels induced by stress reinstates only the anxiety, indicating that it arises from foetal exposure to corticosterone from the maternal circulation. Learning deficits in males may result from a combination of a reduction in testosterone and in aromatase activity, together with the action of other adrenal hormones.     

人脑自适应多尺度功能连接的性别差异

已有脑成像研究展示了男女脑功能差异, 但功能磁共振信号的频率划分通常基于主观经验, 使脑功能性别差异的生物学解释遭遇瓶颈。本文提出人脑自适应多尺度功能连接算法, 刻画功能连接的时空多尺度特性, 揭示出0.06~0.10 Hz的性别差异：男性较强的连接主要与边缘网络和腹侧注意网络有关, 女性较强的连接主要与腹侧注意网络、视觉网络和额顶网络有关。     

Gender and ethnic differences in body image and opposite sex figure preferences of rural adolescents

This study examined whether rural adolescents would report gender and ethnic differences in body image similar to those that have been observed in urban samples. Data were analyzed for 384 rural adolescents (57% African American, 43% Caucasian, mean age 13 years) to determine gender and ethnic differences in body dissatisfaction, body size discrepancy, and current and ideal figure ratings. Females wanted to be smaller and reported more body dissatisfaction than did males. Caucasian females reported the most body dissatisfaction. African Americans reported larger current and ideal figure ratings than did Caucasians. African Americans preferred larger opposite sex figures than did Caucasians. Both African American and Caucasian males selected a larger female figure as ideal than was selected by females. Results demonstrated that gender and ethnic differences exist in body image for rural adolescents. This frequently overlooked population may benefit from further study. Implications of findings and limitations of the study are also discussed.     

Putative sex differences in verbal abilities and language cortex: a critical review

This review brings together evidence from a diverse field of methods for investigating sex differences in language processing. Differences are found in certain language-related deficits, such as stuttering, dyslexia, autism and schizophrenia. Common to these is that language problems may follow from, rather than cause the deficit. Large studies have been conducted on sex differences in verbal abilities within the normal population, and a careful reading of the results suggests that differences in language proficiency do not exist. Early differences in language acquisition show a slight advantage for girls, but this gradually disappears. A difference in language lateralization of brain structure and function in adults has also been suggested, perhaps following size differences in the corpus callosum. Neither of these claims is substantiated by evidence. In addition, overall results from studies on regional grey matter distribution using voxel-based morphometry, indicate no consistent differences between males and females in language-related cortical regions. Language function in Wada tests, aphasia, and in normal ageing also fails to show sex differentiation.     

The possible causes of the sex ratio in stuttering and its implications

The incidence of stuttering has always been reported to be higher in males than in females. Possible causes of the unequal sex ratio include various ascertainment biases, incomplete reporting, social role differences, X-linked inheritance, or a combination of environmental and genetic elements. Each of these factors has been examined against data collected in the large family study of stuttering, and all but one have been eliminated. Only the gene-environment interaction hypothesis can be supported by the data. Statistical analysis confirms that the sex effect in stuttering is real and supports a threshold model for the sex difference. We conclude that the possibility of differences between males and females must be considered in any etiological research in stuttering.     

Sex differences in pain

Are there sex differences in pain? For experimentally delivered somatic stimuli, females have lower thresholds, greater ability to discriminate, higher pain ratings, and less tolerance of noxious stimuli than males. These differences, however, are small, exist only for certain forms of stimulation and are affected by many situational variables such as presence of disease, experimental setting, and even nutritive status. For endogenous pains, women report more multiple pains in more body regions than men. With no obvious underlying rationale, some painful diseases are more prevalent among females, others among males and, for many diseases, symptoms differ between females and males. Sex differences in attitudes exist that affect not only reporting, coping, and responses to treatment, but also measurement and treatment. So many variables are operative, however, that the most striking feature of sex differences in reported pain experience is the apparent overall lack of them. On the other hand, deduction from known biological sex differences suggests that these are powerful sex differences in the operation of pain mechanisms. First, the vaginal canal provides an additional route in women for internal trauma and invasion by pathological agents that puts them at greater risk for developing hyperalgesia in multiple body regions. Second, sex differences in temporal patterns are likely to give rise to sex differences in how pain is "learned" and stimuli are interpreted, a situation that could lead to a greater variability and wider range of pains without obvious peripheral pathology among females. Third, sex differences in the actions of sex hormones suggest pain-relevant differences in the operation of many neuroactive agents, opiate and nonopiate systems, nerve growth factor, and the sympathetic system. Thus, while inductive analysis of existing data demonstrate more similarities than differences in pain experience between females and males, deductive analysis suggests important operational sex differences in its production.     

Evolutionary Neuroandrogenic Theory and Universal Gender Differences in Cognition and Behavior

A theory is proposed that predicts the existence of numerous gender differences in cognition and behavior. The basis for these expectations is the single assumption that females have evolved tendencies to form long term sociosexual alliances with a competent resource provisioner. This assumption is teamed with evidence that males are actually a variant on the female sex with brains masculinized in ways that help them respond to female mating preferences. To orchestrate male responses to female biases in mates, the theory asserts that androgens (male sex hormones) have two main effects on human brain functioning. One is a diminished sensitivity to most environmental stimuli. The other involves shifting cognitive functioning away from the left hemisphere toward a more even and task-specialized hemispheric distribution. Many of the cognitive and behavioral differences between males and females predicted by the theory are described.