Sexual orientation and performance on sexually dimorphic motor tasks

Sex differences in visuospatial cognition- a female advantage in jigsaw puzzle solving

Mentally visualizing objects, understanding relationships between two- or three- dimensional objects, and manipulating objects in space are some examples of visuospatial abilities. Numerous studies have shown that male participants outperform female participants in visuospatial tasks, particularly in mental rotation. One exception is solving jigsaw puzzles. Performance by seven- to eight-year-old girls was found to be superior to that of boys of the same age (Kocijan et al. 2017). No study, however, has confirmed this finding in an adult population, where sex differences are often detectable. Seventy-nine young adult participants were given four different jigsaw puzzles and the Shepard and Metzler mental rotation test (MRT) with two main goals: First, to investigate possible sex differences in jigsaw puzzle solving, and second, to explore a potential relationship between mental rotation and jigsaw puzzle solving. We hypothesized that female participants would outperform males in the jigsaw puzzles but males would outperform females in the MRT. The findings confirmed this hypothesis. Notably, the male performance in jigsaw puzzle solving was attributed to their sex and mediated by their higher MRT scores. These results yielded two key insights. First, they indicate a dissociation between these two visuospatial abilities, jigsaw puzzle solving and mental rotation; and second, female and male participants capitalize on their distinct cognitive strengths when solving visuospatial tasks.

Sex and gender correlates of sexually polymorphic cognition

BACKGROUND

Sexually polymorphic cognition (SPC) results from the interaction between biological (birth-assigned sex (BAS), sex hormones) and socio-cultural (gender identity, gender roles, sexual orientation) factors. The literature remains quite mixed regarding the magnitude of the effects of these variables. This project used a battery of classic cognitive tests designed to assess the influence of sex hormones on cognitive performance. At the same time, we aimed to assess the inter-related and respective effects that BAS, sex hormones, and gender-related factors have on SPC.

METHODS

We recruited 222 adults who completed eight cognitive tasks that assessed a variety of cognitive domains during a 150-min session. Subgroups were separated based on gender identity and sexual orientation and recruited as follows: cisgender heterosexual men (n = 46), cisgender non-heterosexual men (n = 36), cisgender heterosexual women (n = 36), cisgender non-heterosexual women (n = 38), gender diverse (n = 66). Saliva samples were collected before, during, and after the test to assess testosterone, estradiol, progesterone, cortisol, and dehydroepiandrosterone. Psychosocial variables were derived from self-report questionnaires.

RESULTS

Cognitive performance reflects sex and gender differences that are partially consistent with the literature. Interestingly, biological factors seem to better explain differences in male-typed cognitive tasks (i.e., spatial), while psychosocial factors seem to better explain differences in female-typed cognitive tasks (i.e., verbal).

CONCLUSION

Our results establish a better comprehension of SPC over and above the effects of BAS as a binary variable. We highlight the importance of treating sex as a biological factor and gender as a socio-cultural factor together since they collectively influence SPC.

Exploring the sex and gender correlates of cognitive sex differences

The correlates of cognitive sex differences are yet to be fully understood. Many biological and psychosocial factors modulate these cognitive abilities leading to mixed results in the scientific literature. The current study aims to explore the different parameters potentially influencing cognitive abilities acting in synergy. Sex and gender correlates of cognitive functioning were assessed in a sample of individuals ages 18 to 45 years (N = 87) from diverse sexual orientations. Sex hormones were assessed via saliva samples at four timepoints throughout the testing. Gender roles, sexual orientation and socio-demographics were measured via self-report questionnaires. Participants completed mental rotation and verbal fluency tasks. Men performed better than women at mental rotation, while no significant difference was found for verbal fluency. Significant positive associations were observed between estradiol and word fluency for the naturally cycling women compared to the women using oral contraception. While controlling for sex hormones, a significant interaction effect of sex by gender roles was identified for mental rotation among masculine women. These exploratory results suggest an effect principally driven by sex and sex hormones on cognitive performance that will need to be furthered with larger studies.

Men and women differ in the neural basis of handwriting

There is an ongoing debate about whether, and to what extent, males differ from females in their language skills. In the case of handwriting, a composite language skill involving language and motor processes, behavioral observations consistently show robust sex differences but the mechanisms underlying the effect are unclear. Using functional magnetic resonance imaging (fMRI) in a copying task, the present study examined the neural basis of sex differences in handwriting in 53 healthy adults (ages 19–28, 27 males). Compared to females, males showed increased activation in the left posterior middle frontal gyrus (Exner's area), a region thought to support the conversion between orthographic and graphomotor codes. Functional connectivity between Exner's area and the right cerebellum was greater in males than in females. Furthermore, sex differences in brain activity related to handwriting were independent of language material. This study identifies a novel neural signature of sex differences in a hallmark of human behavior, and highlights the importance of considering sex as a factor in scientific research and clinical applications involving handwriting.

Sexual Orientation and Cognitive Ability: A Multivariate Meta-Analytic Follow-Up

A cross-sex shift model of human sexual orientation differences predicts that homosexual men should perform or score in the direction of heterosexual women, and homosexual women in the direction of heterosexual men, in behavioral domains such as cognition and personality. In order to test whether homosexual men and women's cognitive performance was closer to that of heterosexual men or that of heterosexual women (i.e., sex-atypical for their sex and closer to that of the opposite-sex), we conducted a multivariate meta-analysis based on data from our previous meta-analysis (Xu, Norton, & Rahman, 2017). A subset of this data was used and comprised 30 articles (and 2 unpublished datasets) and 244,434 participants. The multivariate meta-analysis revealed that homosexual men were sex-atypical in mental rotation (Hedges' g = -0.36) and the water level test (Hedges' g = -0.55). In mental rotation, homosexual men were in-between heterosexual men and women. There was no significant group difference on spatial location memory. Homosexual men were also sex-atypical on male-favoring spatial-related tasks (Hedges' g = -0.54), and female-favoring spatial-related tasks (Hedges' g = 0.38). Homosexual women tended to be sex-typical (similar to heterosexual women). There were no significant group differences on male-favoring "other" tasks or female-favoring verbal-related tasks. Heterosexual men and women differed significantly on female-favoring "other" tasks. These results support the cross-sex shift hypothesis which predicts that homosexual men perform in the direction of heterosexual women in sex differentiated cognitive domains. However, the type of task and cognitive domain tested is critical.

Sex comparisons of the bilateral deficit in proximal and distal upper body limb muscles

Bilateral deficit (BLD) describes a phenomenon that the force produced during maximal simultaneous bilateral contraction is lower than the sum of those produced unilaterally. The aim of this study was to examine the potential sex-related differences in BLD in upper body proximal and distal limb muscles. Ten men and eight women performed single-joint maximal contractions with their elbow flexors and index finger abductors at separate laboratory visits, during which the maximal isometric voluntary contractions (MVICs) were performed unilaterally and bilaterally with a randomized order in the designated muscle group. Surface electromyographic (EMG) signals were recorded from the prime movers of the designated muscle groups (biceps brachii and first dorsal interosseous) during the maximal contractions. Both men and women demonstrated BLD in their elbow flexors (deficit: men = -11.0 ± 6.3%; women = -10.2 ± 5.0%). Accompanied by this force deficit was the reduced EMG amplitude from the dominant biceps brachii (collapsed across sex: p = 0.045). For the index finger abductors, only men (deficit = -13.7 ± 6.1%), but not women showed BLD. Our results suggested that the BLD in the proximal muscle group is likely induced by the decreased maximal muscle activity from the dominant prime mover. The absence of BLD in women's index finger muscle is largely due to the inter-subject variability possibly related to the sex hormone flux and unique levels of interhemispheric inhibition.

Haptic Distance Ratio Estimation: The Geometry of Space Within the Hands

In the current study of haptic distance perception, 20 younger (median age: 22 years) and 20 older adults (median age: 72 years) used active touch to estimate distance ratios(one length relative to another). Nine tactile stimuli were created from wooden dowels; each consisted of two perpendicular dowels. The stimulus distance ratios ranged from 1.0 to 5.0. Each participant used both hands (without vision) to actively explore (30 s) a single stimulus object on every trial. The task was to numerically estimate the distance ratio. Overall, the participants’ judgments were precise; the overall magnitude of the Pearson r correlation coefficient was 0.943 and did not differ for younger and older adults. While the participants’ judgments were precise, they were not completely accurate: The average slope (of the relationship between actual and judged distance ratios) for all participants was significantly greater than 1.0 (1.15). Surprisingly, differences in manual dexterity had no apparent effect on distance ratio estimates. Older adults apparently retain an excellent ability to perceive distances using their sense of touch. Our results also demonstrate that the geometry of haptic space (at the scale of the hand) is approximately Euclidean in nature (and certainly not merely topological, projective, or affine).

Gender-Based Occupational Segregation and Sex Differences in Sensory, Motor, and Spatial Aptitudes

Research on sex differences in humans documents gender differences in sensory, motor, and spatial aptitudes. These aptitudes, as captured by Dictionary of Occupational Titles (DOT) codes, predict the occupational choices of men and women in the directions indicated by this research. We simulate that eliminating selection on these skills reduces the Duncan index of gender-based occupational segregation by 20 % to 23 % in 1970 and 2012, respectively. Eliminating selection on DOT variables capturing other accounts of this segregation has a smaller impact.

Biological origins of sexual orientation and gender identity: Impact on health

Gynecologic Oncologists are sometimes consulted to care for patients who present with diverse gender identities or sexual orientations. Clinicians can create more helpful relationships with their patients if they understand the etiologies of these diverse expressions of sexual humanity. Multidisciplinary evidence reveals that a sexually dimorphic spectrum of somatic and neurologic anatomy, traits and abilities, including sexual orientation and gender identity, are conferred together during the first half of pregnancy due to genetics, epigenetics and the diversity of timing and function of sex chromosomes, sex-determining protein secretion, gonadal hormone secretion, receptor levels, adrenal function, maternally ingested dietary hormones, fetal health, and many other factors. Multiple layers of evidence confirm that sexual orientation and gender identity are as biological, innate and immutable as the other traits conferred during that critical time in gestation. Negative social responses to diverse orientations or gender identities have caused marginalization of these individuals with resultant alienation from medical care, reduced self-care and reduced access to medical care. The increased risks for many diseases, including gynecologic cancers are reviewed. Gynecologic Oncologists can potentially create more effective healthcare relationships with their patients if they have this information.

Aesthetic as genetic: The epistemological violence of gaydar research

In recent years, “gaydar” has come under increasing scientific scrutiny. Gaydar researchers have found that we can accurately judge sexual orientation at better than chance levels from various nonverbal cues. Why they could find what they did is typically chalked up to gender inverted phenotypic variations in craniofacial structure that distinguish homosexuals. This interpretation of gaydar data (the “hegemonic interpretation”) maintains a construction of homosexuality as both a “natural kind” and an “entitative” category. As a result, culturally and historically contingent markers of homosexuality are naturalized under the guise of gaydar. Of significant relevance to this article’s critique of gaydar research is that the hegemonic interpretation is presented as politically advantageous for LGB people by its authors, an undertheorized assumption that risks sanctioning an epistemological violence with unfortunate, demobilizing sociopolitical consequences. This critique is contextualized within current debates regarding intimate/sexual citizenship and advocates, instead, for a queer political ethic that considers such cultural erasure to be politically untenable.

Factors affecting the results of the functional dexterity test

STUDY DESIGN

Cross-sectional study.

PURPOSE OF THE STUDY

The purpose of this study was to identify which demographic and anthropometric features affect performance (time) on the functional dexterity test (FDT).

METHODS

One hundred fifty-two healthy subjects between the ages of 20 and 80 years were included in this cross-sectional study. Demographic characteristics (age, gender, height, weight, and dominant hand) and anthropometric (the girths of the first 3 fingers) variables were recorded, and the FDT (net time and total score) was performed.

RESULTS

Hand dexterity (time) was slower in participants aged 60 years (35.7 ± 9.4 seconds) and older compared with those aged 40-59 (27.1 ± 7.2 seconds) years and 20-39 (23.9 ± 4.9 seconds) years (P < .001 for both) in dominant side.

DISCUSSION

There was no significant difference between males (29.1 ± 9 in dominant hands and 30.9 ± 9.5 in nondominant hands) and females (27.9 ± 8.4 in dominant hands and 30.8 ± 8.1 in nondominant hands) in all groups in terms of FDT net time. The factors associated with hand dexterity were age in dominant hands (R² = 0.321) and age and thickness of the second and third fingers in nondominant hands (R² = 0.282).

CONCLUSION

FDT scores increased with increasing age for both dominant and nondominant hands. Finger thickness, especially in nondominant hands, should be taken into account while evaluating FDT scores because of its negative effect on dexterity.

LEVEL OF EVIDENCE

Level 2.

Men are More Accurate Than Women in Aiming at Targets in Both near Space and Extrapersonal Space

Men excel at motor tasks requiring aiming accuracy whereas women excel at different tasks requiring fine motor skill. However, these tasks are confounded with proximity to the body, as fine motor tasks are performed proximally and aiming tasks are directed at distal targets. As such, it is not known whether the male advantage on tasks requiring aiming accuracy is because men have better aim or is better in the proximal domain in which the task is usually presented. 18 men ( M age = 20.6 yr., SD = 3.0) and 20 women ( M age = 18.7 yr., SD = 0.9) performed 2 tasks of extrapersonal aiming accuracy (>2 m away), 2 tasks of aiming accuracy performed in near space (< 1 m from them), and a task of fine motor skill. Men outperformed women on both the extrapersonal aiming tasks, and women outperformed men on the task of fine motor skill. However, a male advantage was observed for one of the aiming tasks performed in near space, suggesting that the male advantage for aiming accuracy does not result from proximity.

Male-typical visuospatial functioning in gynephilic girls with gender dysphoria - organizational and activational effects of testosterone

BACKGROUND

Sex differences in performance and regional brain activity during mental rotation have been reported repeatedly and reflect organizational and activational effects of sex hormones. We investigated whether adolescent girls with gender dysphoria (GD), before and after 10 months of testosterone treatment, showed male-typical brain activity during a mental rotation task (MRT).

METHODS

Girls with GD underwent fMRI while performing the MRT twice: when receiving medication to suppress their endogenous sex hormones before onset of testosterone treatment, and 10 months later during testosterone treatment. Two age-matched control groups participated twice as well.

RESULTS

We included 21 girls with GD, 20 male controls and 21 female controls in our study. In the absence of any group differences in performance, control girls showed significantly increased activation in frontal brain areas compared with control boys (p_FWE = 0.012). Girls with GD before testosterone treatment differed significantly in frontal brain activation from the control girls (p_FWE = 0.034), suggesting a masculinization of brain structures associated with visuospatial cognitive functions. After 10 months of testosterone treatment, girls with GD, similar to the control boys, showed increases in brain activation in areas implicated in mental rotation.

LIMITATIONS

Since all girls with GD identified as gynephilic, their resemblance in spatial cognition with the control boys, who were also gynephilic, may have been related to their shared sexual orientation rather than their shared gender identity. We did not account for menstrual cycle phase or contraceptive use in our analyses.

CONCLUSION

Our findings suggest atypical sexual differentiation of the brain in natal girls with GD and provide new evidence for organizational and activational effects of testosterone on visuospatial cognitive functioning.

But Fingerprints Don't Lie, EH?

For more than a decade, feminist theorists have found fault with studies that purport to find significant gender differences with regard to cognitive ability and personality. This article demonstrates the continuing validity of these critiques by considering a series of recent studies that report a higher incidence of dermatoglyphic asymmetry (DA), that is, asymmetry with regard to fingerprint patterns, among females and homosexual males compared to heterosexual males. This analysis suggests that at least some of the key findings reported in these studies are an artifact of the methodology used. It is argued that this case supports the feminist claim that studies whose results reinforce gender stereotypes that prevail in society at large (in this case, the societal construction of male homosexuals as effeminate) are subjected to less scrutiny by the scientific community than those that do not.

Lateralization for Processing Facial Emotions in Gay Men, Heterosexual Men, and Heterosexual Women

This study tested whether male sexual orientation and gender nonconformity influenced functional cerebral lateralization for the processing of facial emotions. We also tested for the effects of sex of poser and emotion displayed on putative differences. Thirty heterosexual men, 30 heterosexual women, and 40 gay men completed measures of demographic variables, recalled childhood gender nonconformity (CGN), IQ, and the Chimeric Faces Test (CFT). The CFT depicts vertically split chimeric faces, formed with one half showing a neutral expression and the other half showing an emotional expression and performance is measured using a "laterality quotient" (LQ) score. We found that heterosexual men were significantly more right-lateralized when viewing female faces compared to heterosexual women and gay men, who did not differ significantly from each other. Heterosexual women and gay men were more left-lateralized for processing female faces. There were no significant group differences in lateralization for male faces. These results remained when controlling for age and IQ scores. There was no significant effect of CGN on LQ scores. These data suggest that gay men are feminized in some aspects of functional cerebral lateralization for facial emotion. The results were discussed in relation to the selectivity of functional lateralization and putative brain mechanisms underlying sexual attraction towards opposite-sex and same-sex targets.

Visual- spatial capacity: gender and sport differences in young volleyball and tennis athletes and non-athletes

Background

In the general population visual-spatial ability is better in males, due to the influence of biological and socio-cultural factors. We know that sport activity improves motor skills. The aim of this work is to determine if these gender differences exist in young athletes. The orientation test described by Terzi and standardized by Cesaroni, used to measure spatial ability, was carried out on 60 volleyball or 60 tennis athletes as well as on 60 non-sporting subjects.

Results

The data analysis revealed a worse performance for non-athletes in comparison with athletes in both components of test (p < 0.0001; p = 0.04), with no differences between the volleyball and tennis groups. As far as gender comparison is concerned, as expected in the non- sport group the males presented better values (p < 0.001; p = 0.006). However in both sports groups there weren’t any gender differences in either part of the test (p = 0.18; p = 0.056).

Conclusions

These results confirm that during athletic preparation in volleyball and tennis the specific training is able to develop spatial ability. Besides, boys and girls have similar performance demands and training experience. It appears that this specific training could be responsible for modifying gender differences in performance of spatial ability during adolescence.

Subjective visual vertical in vestibular disorders measured with the bucket test

CONCLUSION

The 'bucket test' may indicate that patients with known vestibular disorders have spatial orientation deficits but due to the low receiver operating characteristics (ROC) values it is not useful for screening people for vestibular impairments.

OBJECTIVES

1) to verify that patients with unilateral peripheral vestibular weakness (UW) differ from normal subjects on the bucket test, 2) to determine if patients with unilateral benign paroxysmal positional vertigo (BPPV) differ from normal subjects, 3) to determine the sensitivity and specificity of the test.

METHODS

Patients with UW (n = 25) and BPPV (n = 25) were compared to normals (n = 50). Subjects looked into a clean bucket with a vertical line on the bottom, which rested on a table. It was rotated, clockwise or counterclockwise, for three trials per direction until the subject indicated that the line was vertical. The dependent measure was the mean absolute value of the deviations from the true vertical.

RESULTS

Some, but not all, patients' responses differed from normal subjects but responses also differed by age and sex. ROC values were all weak, i.e. < 0.8. No good cut-off points differentiated controls from patients. Thus, although the bucket test is useful for describing spatial deficits in patients this test is not useful for screening people for possible vestibular impairments.

Menstrual cycle-related changes of functional cerebral asymmetries in fine motor coordination

Fluctuating sex hormone levels during the menstrual cycle have been shown to affect functional cerebral asymmetries in cognitive domains. These effects seem to result from the neuromodulatory properties of sex hormones and their metabolites on interhemispheric processing. The present study was carried out to investigate whether functional cerebral asymmetries in fine motor coordination as reflected by manual asymmetries are also susceptible to natural sex hormonal variations during the menstrual cycle. Sixteen right-handed women with a regular menstrual cycle performed a finger tapping paradigm consisting of two conditions (simple, sequential) during the low hormone menstrual phase and the high estrogen and progesterone luteal phase. To validate the luteal phase, saliva levels of free progesterone (P) were analysed using chemiluminescence assays. As expected, normally cycling women showed a substantial decrease in manual asymmetries in a more demanding sequential tapping condition involving four fingers compared with simple (repetitive) finger tapping. This reduction in the degree of dominant (right) hand manual asymmetries was evident during the luteal phase. During the menstrual phase, however, manual asymmetries were even reversed in direction, indicating a slight advantage in favour of the non-dominant (left) hand. These findings suggest that functional cerebral asymmetries in fine motor coordination are affected by sex hormonal changes during the menstrual cycle, probably via hormonal modulations of interhemispheric interaction.

Is homosexuality a paraphilia? The evidence for and against

Whether homosexuality should be described as one among many paraphilic sexual interests or an altogether different dimension of sexual interest has long been discussed in terms of its political and social implications. The present article examined the question instead by comparing the major correlates and other features of homosexuality and of the paraphilias, including prevalence, sex ratio, onset and course, fraternal birth order, physical height, handedness, IQ and cognitive neuropsychological profile, and neuroanatomy. Although those literatures remain underdeveloped, the existing findings thus far suggest that homosexuality has a pattern of correlates largely, but not entirely, distinct from that identified among the paraphilias. At least, if homosexuality were deemed a paraphilia, it would be relatively unique among them, taxonometrically speaking.

The genetics of sex differences in brain and behavior

Biological differences between men and women contribute to many sex-specific illnesses and disorders. Historically, it was argued that such differences were largely, if not exclusively, due to gonadal hormone secretions. However, emerging research has shown that some differences are mediated by mechanisms other than the action of these hormone secretions and in particular by products of genes located on the X and Y chromosomes, which we refer to as direct genetic effects. This paper reviews the evidence for direct genetic effects in behavioral and brain sex differences. We highlight the 'four core genotypes' model and sex differences in the midbrain dopaminergic system, specifically focusing on the role of Sry. We also discuss novel research being done on unique populations including people attracted to the same sex and people with a cross-gender identity. As science continues to advance our understanding of biological sex differences, a new field is emerging that is aimed at better addressing the needs of both sexes: gender-based biology and medicine. Ultimately, the study of the biological basis for sex differences will improve healthcare for both men and women.

Sexual orientation and the auditory system

The auditory system exhibits differences by sex and by sexual orientation, and the implication is that relevant auditory structures are altered during prenatal development, possibly by exposure to androgens. The otoacoustic emissions (OAEs) of newborn male infants are weaker than those of newborn females, and these sex differences persist through the lifespan. The OAEs of nonheterosexual females also are weaker than those of heterosexual females, suggesting an atypically strong exposure to androgens some time early in development. Auditory evoked potentials (AEPs) also exhibit sex differences beginning early in life. Some AEPs are different for heterosexual and nonheterosexual females, and other AEPs are different for heterosexual and nonheterosexual males. Research on non-humans treated with androgenic or anti-androgenic agents also suggests that OAEs are masculinized by prenatal exposure to androgens late in gestation. Collectively, the evidence suggests that prenatal androgens, acting globally or locally, affect both nonheterosexuality and the auditory system.

Sex-related differences in motor learning and performance

Gender differences have been shown across many domains, and motor skills are no exception. One of the most robust findings is a significant sex difference in throwing accuracy, which reflects the advantage of men in targeting abilities. However, little is known about the basis of this difference. To try to dissect possible mechanisms involved in this difference, here we tested for gender variations in a prism adaptation throwing task. We tested 154 subjects in a visuomotor prism adaptation task that discriminates between motor performance, visuomotor adaptation and negative aftereffects. Our results corroborate men's significant better throwing accuracy, although there were no adaptation differences between genders. In contrast, women showed significant larger negative aftereffects, which could be explained by a larger contribution of spatial alignment. These results suggest that different learning mechanisms, like strategic calibration and spatial alignment, may have different contributions in men and women.

Motor activity and imagery modulate the body-selective region in the occipital-temporal area: a near-infrared spectroscopy study

The extrastriate body area (EBA) lies in the occipital-temporal cortex and has been described as a "body-selective" region that responds when viewing other people's bodies. Recently, several studies have reported that EBA is also modulated when the subject moves or imagines moving their own body, even without visual feedback. The present study involved 3 experiments, wherein the first experiment was conducted to examine whether near-infrared spectroscopy (NIRS) could capture any activity in the EBA when viewing images of bodies. The second experiment was designed to elucidate whether this region also responds when the subjects move their own body, and the third to observe whether imagining carrying out a movement would activate EBA. Images of human bodies and chairs were used as the stimuli for the first experiment, simple hand movements carried out by the subject were used for the second and the act of imagining hand movements for the third. Our results confirmed that the region we defined as EBA was clearly activated when the subject viewed images of human bodies, carried out movements of their own body and imagined moving parts of their own body, thus demonstrating the usefulness of NIRS as a new brain imaging method. Moreover, we found a gender-based difference when imagining movement; male subjects showed a greater response than female subjects. This may reflect a gender difference in imagery skills; however, further research is needed to verify this hypothesis.

Activational and organisational effects of gonadal steroids on sex-specific acetylcholine release in the dorsal hippocampus

Acetylcholine (ACh) release in the dorsal hippocampus increases during stress, exploration or learning, exhibiting sex-specific 24-h release profile. We review the role of gonadal steroids on the ACh release in the dorsal hippocampus. In our studies, we found that male rats showed higher extracellular ACh levels than females, but gonadectomy decreased ACh levels in both sexes of rats and subsequently eliminated the sex difference. To examine the sex difference under comparable gonadal steroid levels, we implanted steroid capsules after gonadectomy. Oestradiol supplementation maintained circulating oestradiol to the levels in proestrous female rats, whereas testosterone capsules maintained circulating testosterone to the levels similar to intact male rats. Under comparable gonadal steroids levels, ACh levels were sex-specific. Testosterone replacement in orchidectomised rats clearly restored ACh levels, which were greater than ovariectomised testosterone-primed rats. Similarly, oestradiol replacement in ovariectomised rats successfully restored ACh levels, which were higher than orchidectomised oestradiol-primed rats. These results suggest sex-specific activational effects of gonadal steroids on ACh release. To further examine the organisational effect, female pups were neonatally treated with oil, testosterone, oestradiol, or dihydrotestosterone. These rats were bilaterally ovariectomised and a testosterone capsule was implanted at postnatal week 8. Neonatal treatment of either testosterone or oestradiol clearly increased ACh levels, whereas neonatal dihydrotestosterone treatment failed to change levels. These results suggest that: (i) gonadal steroids maintain the sex-specific ACh release in the dorsal hippocampus and (ii) neonatal activation of oestrogen receptors is sufficient to mediate masculinisation of the septo-hippocampal cholinergic system.

[Sexual dismorphism in schizophrenia]

Recent neuroanatomical studies imply a reversal of normal sexual dimorphism in schizophrenia in several corticolimbic structures, including the anterior cingulate, orbitofrontal cortex and amygdala. Prompted by these reports we have analyzed data of fifteen men and ten women with the diagnosis of schizophrenia who underwent functional magnetic resonance imaging (fMRI) during exposure to two emotion processing tasks. Overall both tests evoked much more extensive and intense cerebral activations in men than in women with schizophrenia. The pattern of obtained results differs significantly from what has been observed in the general population, thus giving support for the recent suggestion of "masculinization" of females and "feminization" of males with schizophrenia. More thorough investigation of a larger number of patients and healthy participants is currently on its way to substantiate this hypothesis.

The brain as the engine of sex differences in the organization of movement in rats

Sex differences in the kinematic organization of non-reproductive behavior are often relegated to byproducts of sex differences in body morphology. We review evidence showing not only that male and female rats organize their posture and stepping differently during a variety of actions, but that these differences arise from sex differences in the organization of movement in the central nervous system (CNS). Indeed, the expression and choice of sex-typical patterns of movement can be altered by CNS injury. The pattern of hormonal regulation of these sex differences is also not organized as commonly held theory would predict. As expected, males castrated shortly after birth are female-typical in their motor organization. Females ovariectomized at birth, however, are male-typical in their patterns of movement. Thus, female-typical patterns of movement organization are not the default form, but rather are dependent on the effects of gonadal steroids to feminize the developing CNS. The implications of these findings are discussed with regards to our understanding of the evolution of sex differences in CNS anatomy and behavior both for animals and humans.

Sex Differences in Performance with the Hand and Arm in near and Far Space: A Possible Effect of Tool Use

Using novel tasks, we tested two predictions from the hunter-gatherer hypothesis concerning sex differences in the motor control of hand and arm and in the visual processing of near and far space. In Study 1 we replicated earlier findings by demonstrating that women scored higher with the hand while men scored higher with the arm. Study 2 tested the motor and visual predictions concurrently and showed that the Muscle*Sex interaction, seen in Study 1, occurs in far as well as near space. However, we failed to confirm that women perform better with visual information from near and men from far space. Instead the relative performance of women and men was the same in far as it was in near space. Drawing on evidence from studies of selective visual neglect we suggest that this outcome arose because tool use causes far space to be re-mapped as near space. Finally, the selective visual neglect literature indicates that the processing of far and near space is located in the ventral and dorsal cortical streams, previously described as two “what”/“where” visual systems. We draw attention to their additional “there”/“here” functions that are sex dimorphic and, as we have shown, modulated by tool use.

Testing Predictions from the Hunter-Gatherer Hypothesis — 2: Sex Differences in the Visual Processing of near and Far Space

Here, in the second of two linked reports, we focus on sex differences in visual processing. Study 1 presented a time estimation task in virtual space and generated the predicted Space*Sex interaction with men performing significantly better in far than in near space. Study 2 used a laboratory-based puzzle completion task in which participants saw their hands and the puzzle in far or near space. This time women performed significantly better in near than far space. Study 3 simplified the puzzle completion task. Once again the predicted Space*Sex interaction was significant but with both sexes showing significantly different performances: women better in near, men in far space. These findings are compatible with an evolutionary origin as predicted by the hunter-gatherer hypothesis. Far and near space are processed in the ventral and dorsal streams, two cortical regions more widely known as the “what” and “where” visual systems. To those traditional descriptions we suggest adding that the two streams are sex-dimorphic, with the ventral “there” system interacting with far space and favored in men and the dorsal “here” system interacting with near space and favored in women. Future studies of visual systems should consider the impact of sex differences and the spatial location of stimulus presentations.

Sex differences in cortical and subcortical recruitment during simple and complex motor control: an fMRI study

In this study, we compared brain activation patterns in men and women during performance of a fine motor task, in order to investigate the influence of motor task complexity upon asymmetries of hemispheric recruitment. Thirty-three right-handed participants (17 males, 16 females) performed a self-paced finger-tapping task comprising three conditions of increasing complexity with both the dominant and the non-dominant hand. Imaging results demonstrated significant sex differences in brain activation patterns. While women showed significantly larger activation of ipsi- and contralateral task-related cortical areas than men, men exhibited significantly stronger subcortical activation in striatal regions. The observed activation differences may reflect sex differences in control of voluntary motor skills related to differential emphasis upon cortical and subcortical correlates of motor sequence processing, as well as differences in hemispheric recruitment, by means of which men and women can nevertheless achieve comparable motor performance.

Sex difference in the 24-h acetylcholine release profile in the premotor/supplementary motor area of behaving rats

The sex differences in various motor functions suggest a sex-specific neural basis in the nonprimary or primary motor area. To examine the sex difference in the 24-h profile of acetylcholine (ACh) release in the rostral frontal cortex area 2 (rFr2), which is equivalent to the premotor/supplementary motor area in primates, we performed an in vivo microdialysis study in both sexes of rats fed pelleted or powdered diet. The dialysate was automatically collected from the rFr2 for 24 h under freely moving conditions. Moreover, the number of cholinergic neurons in the nucleus basalis magnocellularis (NBM) was examined. Further, to confirm the relation between ACh release in the rFr2 and motor function, the spontaneous locomotor activity was monitored for 24 h. Both sexes showed a distinct 24-h rhythm of ACh release, which was high during the dark phase and low during the light phase. Female rats, however, showed a greater ACh release and more cholinergic neurons in the NBM than male rats. Similarly, spontaneous locomotor activity also showed a 24-h rhythm, which paralleled the changes in ACh release in both sexes, and these changes were again greater in female rats than in male rats. In addition, feeding with powdered diet significantly increased the ACh release and spontaneous locomotor activity. The present study is the first to report the sex difference in the 24-h profile of ACh release in the rFr2 in rats. The sex specific ACh release in the rFr2 may partly contribute to the sex difference in motor function in rats.

Gender-specific movement strategies using a computer-pointing task

Females typically demonstrate a movement time advantage for tasks requiring high levels of manual dexterity, whereas males are notably better at targeting activities. According to D. Kimura (2000), the hunter-gatherer hypothesis primarily accounts for those performance advantages; that dichotomy fails, however, when one makes movement outcome predictions for tasks that are not clearly fine-motor or interceptive in nature. Investigators have recently proposed that time constraints (M. Peters, 2005) and gender-specific response style differences (M. Peters & P. Campagnaro, 1996; L. E. Rohr, 2006) affect motor performance. Here, the author used a computer-pointing task measuring both movement error and movement time in 16 participants to further investigate response style differences. Kinematic and linear regression analyses between resultant error and both movement time and task difficulty reinforced the notion that gender-specific movement biases emphasize speed and accuracy, respectively, for men and women.

Associations among gender-linked toy preferences, spatial ability, and digit ratio: evidence from eye-tracking analysis

Eye-tracking technology was used to monitor eye-movements in 64 adults (age range, 18-22 years) during simultaneous presentation of "masculine" and "feminine" toys. Women and men who showed more visual fixations on male-typical toys compared to female-typical toys had significantly better targeting ability and smaller (i.e., more masculine) digit ratios, a putative marker of prenatal androgen levels. In contrast, individuals with visual preferences for female-typical or male-typical toys did not differ in mental rotations ability and in their retrospective reports of childhood gender-linked activities. The finding that targeting ability and digit ratios varied according to visual preferences for gender-linked toys suggests that prenatal androgens promote enduring preferences for male-typical objects and indicate further that some gender-linked traits vary according to the direction of a visual preference for gender-linked toys. Visual preferences derived from eye-tracking, therefore, may be a useful supplement to current measures of psychosexual differentiation in hormone-behavior research, particularly because eye-movements are not dependent on verbal abilities or subjective evaluations of behavior.

Upper and Lower Limb Reciprocal Tapping: Evidence for Gender Biases

According to D. Kimura's (2000) interpretation of the hunter-gatherer hypothesis, men are better at targeting tasks and women are better at fine-motor tasks because of their evolutionary experiences. The author applied that hypothesis to a lower limb pointing task, a task uninfluenced by hunting and gathering experience throughout history. Participants (39 women, 35 men) completed the P. M. Fitts (1954) task by using both their dominant right hand and foot. Results suggested that for both the upper and lower limbs, men move faster, particularly for the more difficult tasks. The hunter-gatherer hypothesis does not predict those data; rather, linear regression data suggest that gender differences in movement strategies affect motor performance. The author proposes that men and women preferentially adopt distinct strategies emphasizing speed for men and accuracy for women.

Sexually dimorphic postural adjustments are used in a skilled reaching task in the rat

Sex differences occur not only in the sexual repertoire of animals but also are evident in other aspects of movement. The present study asked whether sexually dimorphic motor behavior extends to the skilled movements used in reaching for food in the rat. Because we have previously shown that males and females are sexually dimorphic in their organization of lateral and rotatory movements and because postural adjustments are incorporated into skilled movements, both body posture and limb movements were examined during a skilled reaching task. Male and female Long-Evans rats were filmed, from both the front and ventral views and their stepping patterns, postural adjustments and forelimb movements, during a successful reach were analyzed. While males and females did not differ in forelimb movements, they were significantly different in how they approached and oriented their body to the food item during a successful reach. These results are discussed in relation to the dissociation of skilled movement from postural adjustments, sex-dependent alterations following CNS injury, and the neural and evolutionary basis of sex differences in movement organization.

A new method of administering the Grooved Pegboard Test: Performance as a function of handedness and sex

The purpose of the present study was twofold: first to examine the influences of sex and handedness on manual performance on the Grooved Pegboard Test; and secondly to provide normative data for two versions (Place and Remove tasks) of the Grooved Pegboard Test, as previous work (Bryden & Roy, 1999) had suggested that the Remove task of the Grooved pegboard may provide a purer measure of motor speed of the two hands than the standard administration of the Grooved Pegboard Test. One hundred and fifty-three (47 males and 106 females) participants completed the Grooved Pegboard Test. Individuals performed the standard version of the Grooved Pegboard Test (Place task) and a novel version of the test (Remove task). In the standard version, participants were timed on their speed for placing the pegs, while in the novel version they were timed on their speed for removing the pegs. Results confirmed previously noted hand and sex differences in the Place task of the Grooved Pegboard Test, as well as the lack of effect of handedness on performance (Bornstein, 1995; Ruff & Parker, 1993). Significant performance differences between the hands were also noted for the Remove task. Findings also indicated that the Remove task was sensitive to sex and handedness effects.

Fluctuating asymmetry, second to fourth finger length ratios and human sexual orientation

Sexual orientation in humans may be influenced by levels of prenatal sex steroids which canalise neurodevelopment along sex-typical (heterosexual) or sex-atypical (homosexual) lines. Some evidence for sexual-orientation-related differences in putative somatic markers of prenatal sex hormones supports this view. A competing theory asserts that human homosexuality is due to developmental instability (DI) because it represents a shift from the species-typical pattern of heterosexual orientation. Evidence for elevated rates of non-right handedness among homosexuals provides limited support for this account. The current study tested both theories by examining nine bilateral somatic traits in 120 healthy heterosexual and homosexual men and women in order to compute second to fourth finger length ratios (2D:4D), a measure ascribed to levels of prenatal sex steroids, and fluctuating asymmetry (FA), a measure of DI. Homosexual men and women had significantly lower right hand 2D:4D ratios (even after controlling for handedness, height and weight differences) in comparison to heterosexuals, but sexual orientation did not relate to composite FA scores. The findings constrain the number of possible neurodevelopmental pathways responsible for sexual orientation in humans.

A Role for 5Alpha-Reductase Activity in the Development of Male Homosexuality?

Higher body hair with lower mesmorphism ratings were observed in Caucasian homosexual men compared with the general male population, reflecting elevated 5alpha-reductase (5alphaR) activity, and higher dihydrotestosterone-to-testosterone (DHT-to-T) ratio, in sharp contrast to 46,XY 5alphaR 2 deficiency subjects, who are often born with ambiguous, or female genitalia, but tend to grow up to be muscular, heterosexual men with very little body hair, or beard. One study also showed them scoring around dull normal IQs. A greater prevalence of liberal body hair growth in men with higher IQs and/or educational levels was also observed in several samples. The exceptions to this statistical trend are too unsettling, however. Nevertheless, the results of a number of published studies, including one showing higher DHT-to-T ratio in homosexual men, done with different objectives over a span of 80 years, together strongly support these findings. Furthermore, in an animal model, "cognitive-enhancing effects" of "5alpha-reduced androgen [metabolites]" were recently demonstrated.

Throwing accuracy during prism adaptation: male advantage for throwing accuracy is independent of prism adaptation rate

Previous studies have found that men are more accurate at throwing an object at a target than are women, independent of experience. However, these studies' results are based on average scores from multiple trials. As such, it is unknown whether the male advantage results from superior throwing accuracy or from a superior ability to calibrate subsequent throws. This study examined whether men can calibrate repeated throws more quickly and accurately than women, 25 men and 30 women were required to throw velcro-covered balls at a carpet-covered target, both with and without 10-diopter prism lenses. Participants had multiple trials in both conditions. Analyses examined whether there was a sex difference in the rate of adaptation to the prism lenses (as indicated by calibration of subsequent throws), instead of simply averaging all throwing accuracy scores and looking for an overall sex difference. Men threw the balls significantly more accurately than women, both with and without the prism lenses. However, there was no significant sex difference found on the rate of prism adaptation, as measured by improvement across the trials, i.e., calibration. Although men were more accurate at throwing balls overall, there was no sex difference in calibration of subsequent throws in adapting to the prism lenses, therefore indicating that the male advantage in throwing accuracy does not result from superior ability to calibrate subsequent throws but rather from superior throwing accuracy overall.

Homoerotic development during childhood and adolescence

To adequately understand the diversity of child and adolescent homoeroticism, a differential developmental trajectories perspective is proposed that integrates recent research about the development of sexual orientation, sexual behavior, and sexual identity. Only the latter two can be altered therapeutically. Biologic theories of homosexuality are reviewed. Homoerotic youth are shown to be similar and dissimilar to heterosexual youth; more variability occurs within than among sexual orientation groups. Contemporary homoerotic youth recognize their sexuality, self-label, and accept their sexuality at earlier ages than previous generations and many are rejecting traditional identity labels. Clinical recommendations offer ways to assess sexual orientation and help patients to achieve acceptance of their sexuality.

Advocacy for women's health should include lesbian health

Although research confirms that homosexuality is a normal expression of human sexuality, established scientific studies are often not reflected in laws and judicial opinions for lesbians with regard to employment, taxation, pensions, disability, healthcare, immigration, military service, marriage, custody, and adoption. The expression of homosexual attraction or behavior is sometimes met by disdain or violence. Psychological and epidemiological research confirms that the public discriminatory attitudes and second-class legal status cause physical, emotional, and financial harm to lesbians, their families, and their children. Some lesbians experience discrimination in healthcare and avoid routine primary healthcare. To decrease the harm, and improve the health of lesbians, medical institutions can include sexual orientation and gender identity in their nondiscrimination policies and offer domestic partner coverage in employment benefits. Our specialty societies should review current laws and judicial opinions and advocate for change. Further, specialty societies can effect change by issuing policy statements about issues of orientation and by writing orientation/identity curricula for public schools, colleges, and postcollegiate education to improve their accuracy, reduce sexually transmitted diseases, delay sexual activity, and reduce morbidity from homophobic violence.

Have sex differences in spatial ability evolved from male competition for mating and female concern for survival?

Drawing on the theoretical and empirical foundations of two evolutionary models, we argue that, among humans and other mammals, a twofold selection process would parsimoniously account for sex-linked advantages in spatial contexts. In males, a superiority for both solving navigation-related spatial problems and understanding physical principles that apply to the behavior of projectiles could have been inherited from mating-oriented male competition involving extensive ranging and agonistic displays. In females, a form of superior spatial memory may have been shaped in relation to a costly reproduction system compelling them to safeguard their survival and that of their offspring by fostering low-risk strategies consisting of restricted navigation as well as concentration on nearby spatial cues. Based on the combined action of competition and survival pressures, we submit new predictions as to spatial sex differences in several species including humans.