Female-typical Pattern Research Articles

Sex-related patterns in the electroencephalogram and their relevance in machine learning classifiers.

Deep learning is increasingly being proposed for detecting neurological and psychiatric diseases from electroencephalogram (EEG) data but the method is prone to inadvertently incorporate biases from training data and exploit illegitimate patterns. The recent demonstration that deep learning can detect the sex from EEG implies potential sex-related biases in deep learning-based disease detectors for the many diseases with unequal prevalence between males and females. In this work, we present the male- and female-typical patterns used by a convolutional neural network that detects the sex from clinical EEG (81% accuracy in a separate test set with 142 patients). We considered neural sources, anatomical differences, and non-neural artifacts as sources of differences in the EEG curves. Using EEGs from 1140 patients, we found electrocardiac artifacts to be leaking into the supposedly brain activity-based classifiers. Nevertheless, the sex remained detectable after rejecting heart-related and other artifacts. In the cleaned data, EEG topographies were critical to detect the sex, but waveforms and frequencies were not. None of the traditional frequency bands was particularly important for sex detection. We were able to determine the sex even from EEGs with shuffled time points and therewith completely destroyed waveforms. Researchers should consider neural and non-neural sources as potential origins of sex differences in their data, they should maintain best practices of artifact rejection, even when datasets are large, and they should test their classifiers for sex biases.

Patterns of Genital Sexual Arousal in Transgender Men

Most men show genital sexual arousal to one preferred gender. Most women show genital arousal to both genders, regardless of their sexual preferences. There is limited knowledge of whether this difference is driven by biological sex or gender identity. Transgender individuals, whose birth sex and gender identity are incongruent, provide a unique opportunity to address this question. We tested whether the genital responses of 25 (female-to-male) transgender men followed their female birth sex or male gender identity. Depending on their surgical status, arousal was assessed with penile gauges or vaginal plethysmographs. Transgender men’s sexual arousal showed both male-typical and female-typical patterns. Across measures, they responded more strongly to their preferred gender than to the other gender, similar to (but not entirely like) 145 cisgender (nontransgender) men. However, they still responded to both genders, similar to 178 cisgender women. In birth-assigned women, both gender identity and biological sex may influence sexual-arousal patterns.

Potential contribution of progesterone receptors to the development of sexual behavior in male and female mice

We previously showed that estradiol can have both defeminizing and feminizing effects on the developing mouse brain. Pre- and early postnatal estradiol defeminized the ability to show lordosis in adulthood, whereas prepubertal estradiol feminized this ability. Furthermore, we found that estradiol upregulates progesterone receptors (PR) during development, inducing both a male-and female-typical pattern of PR expression in the mouse hypothalamus. In the present study, we took advantage of a newly developed PR antagonist (ZK 137316) to determine whether PR contributes to either male- or female-typical sexual differentiation. Thus groups of male and female C57Bl/6j mice were treated with ZK 137316 or OIL as control: males were treated neonatally (P0–P10), during the critical period for male sexual differentiation, and females were treated prepubertally (P15–P25), during the critical period for female sexual differentiation. In adulthood, mice were tested for sexual behavior. In males, some minor effects of neonatal ZK treatment on sexual behavior were observed: latencies to the first mount, intromission and ejaculation were decreased in neonatally ZK treated males; however, this effect disappeared by the second mating test. By contrast, female mice treated with ZK during the prepubertal period showed significantly less lordosis than OIL-treated females. Mate preferences were not affected in either males or females treated with ZK during development. Taken together, these results suggest a role for PR and thus perhaps progesterone in the development of lordosis behavior in female mice. By contrast, no obvious role for PR can be discerned in the development of male sexual behavior.

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.

Handedness, Functional Cerebral Hemispheric Lateralization, and Cognition in Male-to-Female Transsexuals Receiving Cross-Sex Hormone Treatment

This study examined the impact of sex hormones on functional cerebral hemispheric lateralization and cognition in a group of male-to-female transsexuals receiving cross-sex hormone therapy compared to eugonadal men with a male gender identity. Cerebral lateralization was measured with a handedness questionnaire and a visual-split-field paradigm and cognitive tests sensitive to sex hormone exposure (identical pictures, 3-D mental rotation, building memory) were also administered. Endocrine measures on the day of participation for transsexual and control subjects included total testosterone, free testosterone, estradiol, gonadotropins, and sex hormone binding globulin concentrations. Compared to controls, male-to-female transsexuals had elevated estradiol and sex hormone binding globulin concentrations and suppressed testosterone concentrations. Transsexual subjects showed a trend toward less exclusive right-handedness than controls. No group differences were observed on the visual-split-field or cognitive tasks. No direct associations were observed between endocrine measures and the laterality measures and cognitive performance. Previous observations of female-typical patterns in cerebral lateralization and cognitive performance in male-to-female transsexuals were not found in the current study.

The Brain-Sex Theory of Occupational Choice: A Counterexample

The brain-sex theory of occupational choice suggests that males and females in male-typical careers show a male pattern of cognitive ability in terms of better spatial than verbal performance on cognitive tests with the reverse pattern for females and males in female-typical careers. These differences are thought to result from patterns of cerebral functional lateralisation. This study sought such occupationally related effects using synonym generation (verbal ability) and mental rotation (spatial ability) tasks used previously. It also used entrants to these careers as participants to examine whether patterns of cognitive abilities might predate explicit training and practice. Using a population of entrants to sex-differentiated university courses, a moderate occupational effect on the synonym generation task was found, along with a weak (p < .10) sex effect on the mental rotation task. Highest performance on the mental rotation task was by female students in fashion design, a female-dominated occupation which makes substantial visuospatial demands and attracts many students with literacy problems such as dyslexia. This group then appears to be a counterexample to the brain-sex theory. However, methodological issues surrounding previous studies are highlighted: the simple synonym task appears to show limited discrimination of the sexes, leading to questions concerning the legitimacy of inferences about lateralisation based on scores from that test. Moreover, the human figure-based mental rotation task appears to tap the wrong aspect of visuospatial skill, likely to be needed for male-typical courses such as engineering. Since the fashion-design career is also one that attracts disproportionately many male students whose sexual orientation is homosexual, data were examined for evidence of female-typical patterns of cognitive performance among that subgroup. This was not found. This study therefore provides no evidence for the claim that female-pattern cerebral functional lateralisation is likely in gay males.

Neonatal and Pubertal, but Not Adult, Ovarian Steroids Are Necessary for the Development of Female-Typical Patterns of Dodging to Protect a Food Item.

Rats protect food by dodging horizontally away from a conspecific. Females and males use different movement and stepping patterns to execute a dodge. An unresolved question is whether exposure to ovarian steroids in females is necessary for the development of the female-typical pattern. Females ovariectomized neonatally and prior to puberty use a combination of male and female tactics. Pregnant females, however, use a female-typical pattern of dodging, suggesting that the patterns used by prepubertal ovariectomized females are not due to their increase in body mass. Thus, the contribution of ovarian steroids to the development of female-typical patterns of behavior needs to be studied further at both a behavioral and neural level with regard to the organization of movement.

Sex differences in play fighting revisited: traditional and nontraditional mechanisms of sexual differentiation in rats.

In the traditional model for sexual differentiation in mammals, the female phenotype is the default condition. That is, the female-typical pattern will persist unless acted upon by hormones early in development. The frequency of play fighting in rats, as in most other mammals, is sexually differentiated, and conforms to the traditional model. Males engage in more play fighting than females, and this can be reduced to female-typical levels by neonatal castration. Furthermore, females can be induced to play fight at male-typical levels if treated with testosterone neonatally. Fractionation of play fighting into its constituent components, attack and defense, reveals that it is the frequency of attack that is sexually differentiated, not the likelihood of defense. However, in males, defensive behavior changes at puberty so that the play becomes "rougher." For males to switch to this rougher form of play fighting, they have to be androgenized perinatally. Hence, for males, this second aspect of play fighting that is sexually differentiated also follows the traditional model. In marked contrast, development of the female-typical pattern does not. Neonatal treatment of females with testosterone has no effect; at puberty, they still show the female-typical pattern. On the the other hand, ovariectomy, either at birth or at weaning, leads to females exhibiting the male-typical transition to rougher play fighting at puberty. That is, ovarian hormones appear to actively inhibit the expression of a male-typical trait in females. Play fighting, then, is a mixture of traits, with some features conforming to the traditional model and some not. For some phenotypic features, ovarian hormones appear to exert an active role in their development.

Organization of sex-typical patterns of defense during food protection in the rat: The role of the opponent's sex

Feeding rats defend a food item from an approaching conspecific by turning away, laterally, about 180°. Females and males use a different composition of movements and stepping patterns to perform these defensive dodges. This study was designed to examine the role of the robber's sex on the execution of sex-typical patterns of dodging. All subjects were tested with a partner of each sex. During dodging, females used the female-typical pattern of pivoting around the pelvis, and males used the male-typical midbody pivot, irrespective of the robber's sex. These findings show that the sex-typical patterns of dodging are not determined by the sex of the partner. Females and males however, differed in how they were oriented towards a same sex robber at the end of the dodge. This suggests that while male and female robbers must pose different defensive problems, these differences are dealt with by modifying the sex-typical pattern of dodging rather than by switching to the dodge pattern of the opposite sex. This further suggests that the differences in the composition of the dodge pattern in males and females are not due to extrinsic contingencies, but rather, are due to intrinsic differences in the sex-typical organization of defensive motor patterns. Aggr. Behav. 23:197–214, 1997.© 1997 Wiley-Liss, Inc.