Competition, testosterone, and adult neurobehavioral plasticity

Influence of horse demographics, country of training and race distance on the rating of Thoroughbreds

The aim of the research was to assess how age, sex, sire, country of foaling, country of training and race distance influenced the international racing and performance of Thoroughbreds. The research was based on performance ratings of 6216 horses assigned by the International Federation of Racing Authorities between 2004 and 2022. The most common sex was stallion (58.54 %) and more than half of the population consisted of 3- and 4-year-old horses (54.68 %). The majority of the horses had the USA as their country of foaling (25.92 %) and also as their country of training (24.87 %). The sire with the largest number of offspring in the International Federation of Horseracing Authorities (IFHA) databases was Galileo (IRE) (193 horses). Four of the 10 most frequently represented sires belonged to the Sadler's Wells (USA) paternal line. The analysis of the statistics in the database as a whole established a significant (p < 0.001 ) influence of all observed factors. Stallions achieved a significantly higher rating (117.85) compared to geldings (117.17) and mares (117.13). The horses originating in Ireland achieved a statistically higher rating (117.99) than horses from Argentina, Australia, Brazil, New Zealand, a group of other countries designated "Others" and South Africa. Statistically conclusive differences were found between horses trained in Ireland (118.80) and all other countries except Great Britain and France. Five of the 10 sires with the best offspring rating belong to the Mr. Prospector (USA) paternal line.

No Compelling Evidence that Self-Reported Personality Traits Explain Basal Testosterone and Cortisol’s Associations with Status-Relevant Behavior

Objective

A goal of behavioral neuroendocrinology is to understand how basal hormone levels relate to behavior. Studies of human participants sometimes measure self-reported personality traits, in addition to or instead of direct behavioral observation. Although personality traits often predict their respective behaviors, whether personality explains hormone-behavior relationships remains unclear.

Methods

We obtained data from eight previous studies (total N = 985) that examined baseline testosterone and cortisol as predictors of status-relevant behavior (competitiveness, dominance, risk-taking, aggression, affiliation, and social status). We tested whether the previously reported hormone-behavior relationships are mediated by self-reported personality traits (e.g., trait dominance, prestige, extraversion). As a secondary research question, we also tested whether trait dominance moderated the testosterone-behavior relationships.

Results

As expected, self-reported personality traits often predicted status-relevant behaviors, but there was little evidence that traits also correlated with basal testosterone or the testosterone × cortisol interaction. Across all eight studies, personality traits did not significantly mediate hormone-behavior relationships. Indeed, the effect sizes of the hormone-behavior relationships were robust to the inclusion of personality traits as covariates. Further, we did not find strong or consistent evidence that trait dominance moderates the testosterone-behavior association.

Conclusion

Results suggest that basal testosterone and cortisol predict status-related behavior independent of self-reported personality. We discuss how these results may have broader implications for the physiological mechanisms by which testosterone and cortisol influence behavior, a process that could be unconscious and automatic. We also discuss alternative explanations, limitations, and future directions.

Sex differences matter: Males and females are equal but not the same

Sex differences between males and females can be detected early in life. They are present also later even to a much greater extent affecting our life in adulthood and a wide spectrum of physical, psychological, cognitive, and behavioral characteristics. Moreover, sex differences matter also in individual's health and disease. In this article, we reviewed at first the sex differences in brain organization and function with respect to the underlying biological mechanisms. Since the individual functional differences in the brain, in turn, shape the behavior, sex-specific psychological/behavioral differences that can be observed in infants but also adults are consequently addressed. Finally, we briefly mention sex-dependent variations in susceptibility to selected disorders as well as their pathophysiology, diagnosis, and response to therapy. The understanding of biologically determined variability between males and females can have important implications, especially in gender-specific health care. We have the impression that it is very important to emphasize that sex matters. Males and females are differently programmed by nature, and it must be respected. Even though we as males and females are not the same, we would like to emphasize that we are still equal and together form a worthy colorful continuum.

Evidences for Mutant Huntingtin Inducing Musculoskeletal and Brain Growth Impairments via Disturbing Testosterone Biosynthesis in Male Huntington Disease Animals

Body weight (BW) loss and reduced body mass index (BMI) are the most common peripheral alterations in Huntington disease (HD) and have been found in HD mutation carriers and HD animal models before the manifestation of neurological symptoms. This suggests that, at least in the early disease stage, these changes could be due to abnormal tissue growth rather than tissue atrophy. Moreover, BW and BMI are reported to be more affected in males than females in HD animal models and patients. Here, we confirmed sex-dependent growth alterations in the BACHD rat model for HD and investigated the associated contributing factors. Our results showed growth abnormalities along with decreased plasma testosterone and insulin-like growth factor 1 (IGF-1) levels only in males. Moreover, we demonstrated correlations between growth parameters, IGF-1, and testosterone. Our analyses further revealed an aberrant transcription of testosterone biosynthesis-related genes in the testes of BACHD rats with undisturbed luteinizing hormone (LH)/cAMP/PKA signaling, which plays a key role in regulating the transcription process of some of these genes. In line with the findings in BACHD rats, analyses in the R6/2 mouse model of HD showed similar results. Our findings support the view that mutant huntingtin may induce abnormal growth in males via the dysregulation of gene transcription in the testis, which in turn can affect testosterone biosynthesis.

Aging, testosterone, and neuroplasticity: friend or foe?

Neuroplasticity or neural plasticity implicates the adaptive potential of the brain in response to extrinsic and intrinsic stimuli. The concept has been utilized in different contexts such as injury and neurological disease. Neuroplasticity mechanisms have been classified into neuroregenerative and function-restoring processes. In the context of injury, neuroplasticity has been defined in three post-injury epochs. Testosterone plays a key yet double-edged role in the regulation of several neuroplasticity alterations. Research has shown that testosterone levels are affected by numerous factors such as age, stress, surgical procedures on gonads, and pharmacological treatments. There is an ongoing debate for testosterone replacement therapy (TRT) in aging men; however, TRT is more useful in young individuals with testosterone deficit and more specific subgroups with cognitive dysfunction. Therefore, it is important to pay early attention to testosterone profile and precisely uncover its harms and benefits. In the present review, we discuss the influence of environmental factors, aging, and gender on testosterone-associated alterations in neuroplasticity, as well as the two-sided actions of testosterone in the nervous system. Finally, we provide practical insights for further study of pharmacological treatments for hormonal disorders focusing on restoring neuroplasticity.

Hormonal contraceptives as disruptors of competitive behavior: Theoretical framing and review

Emerging evidence suggests that hormonal contraceptives (HCs) impact psychological outcomes through alterations in neurophysiology. In this review, we first introduce a theoretical framework for HCs as disruptors of steroid hormone modulation of socially competitive attitudes and behaviors. Then, we comprehensively examine prior research comparing HC users and non-users in outcomes related to competition for reproductive, social, and financial resources. Synthesis of 46 studies (n = 16,290) led to several key conclusions: HC users do not show the same menstrual cycle-related fluctuations in self-perceived attractiveness and some intrasexual competition seen in naturally-cycling women and, further, may show relatively reduced status- or achievement-oriented competitive motivation. However, there a lack of consistent or compelling evidence that HC users and non-users differ in competitive behavior or attitudes for mates or financial resources. These conclusions are tentative given the notable methodological limitations of the studies reviewed. Implications and recommendations for future research are discussed.

Desire for Success Awakens: Proof of Competence Restoration in a Non-competitive Environment

Pioneering studies reported that individuals who worked on a highly difficult task and experienced competence frustration beforehand would activate a restorative process and show enhanced autonomous motivation in a subsequent irrelevant activity. In this follow-up study, we explored the effect of prior competition outcome on one’s autonomous motivation in a subsequent non-competitive environment. According to our experimental manipulation, participants were randomly assigned to two treatment groups (a winning group and a losing group) and a control group. The experiment lasted for three sessions. Participants in the control group completed a single-player stop-watch (SW) task all along, while those in both treatment groups worked on a competitive SW task and competed for monetary rewards during Session 2 only. Electrophysiological data in Session 1 serve as the baseline and measure one’s trait-level autonomous motivation towards the SW game. For participants in the losing group, more pronounced difference wave of feedback-related negativity was observed in Session 3 compared with Session 1, suggesting enhanced autonomous motivation in Session 3. Such a pattern was observed in neither the winning group nor the control group. These results suggested that failure in a prior competition would activate one’s competence restoration in a subsequent non-competitive environment. Task difficulty and social competition are varied sources of competence frustration. Thus, our findings advanced understanding of the competence restorative process and helped clarify the dynamics between competition and human motivation.

Testosterone and the Brain: From Cognition to Autism

Sex and gender matter in all aspects of life. Humans exhibit sexual dimorphism in anatomy, physiology, but also pathology. Many of the differences are due to sex chromosomes and, thus, genetics, other due to endocrine factors such as sex hormones, some are of social origin. Over the past decades, huge number of scientific studies have revealed striking sex differences of the human brain with remarkable behavioral and cognitive consequences. Prenatal and postnatal testosterone influence brain structures and functions, respectively. Cognitive sex differences include especially certain spatial and language tasks, but they also affect many other aspects of the neurotypical brain. Sex differences of the brain are also relevant for the pathogenesis of neuropsychiatric disorders such as autism spectrum disorders, which are much more prevalent in the male population. Structural dimorphism in the human brain was well-described, but recent controversies now question its importance. On the other hand, solid evidence exists regarding gender differences in several brain functions. This review tries to summarize the current understanding of the complexity of the effects of testosterone on brain with special focus on their role in the known sex differences in healthy individuals and people in the autism spectrum.

Litter sex composition influences competitive performance during first reproduction in male mouse lemurs

In litter-bearing mammals, conditions experienced early in life can have long-lasting consequences on adult behavioral and physiological phenotypes, including reproductive fitness and survival. Using data from a large database, we focused our analysis on the consequences of litter composition on the reproductive performance of 131 mouse lemur males during their first breeding season. For male offspring, body mass at birth and at weaning only depended on the litter size (from one to 3), with the lowest values in triplets. Early growth had no relationship with the future reproductive success when males entered their first breeding season. When mouse lemurs were kept in groups with 2 or 3 competitors, males entered sexual competition for priority access to females in estrus, leading to a hierarchy with the dominant male ensuring the successful mating of the females. Genetic paternity tests showed that males born in same-sex litters (M, MM, MMM) were more competitive and fathered more offspring than males born in mixed-sex litters (MF, MMF, MFF), indicating the negative impact of a sister on male reproductive success. However, testosterone levels were unrelated to early growth or litter sex composition but were dependent on social interactions during sexual competition, with higher values in successful males. The effects of litter composition on the mating success of male mouse lemurs might mainly occur through social interactions between male offspring born in same-sex litters. Play fighting between juvenile males could play a major role in their acquisition of the skills required to succeed in sexual competition.

Testosterone reactivity to competition and competitive endurance in men and women

Transient shifts in testosterone occur during competition and are thought to positively influence dominance behavior aimed at enhancing social status. However, individual differences in testosterone reactivity to status contests have not been well-studied in relation to real-time expressions of competitive behavior among men and women. This research tests the association between changes in endogenous testosterone levels during competition and performance in terms of competitive endurance. Participant sex, social presence, and relative status outcomes (e.g., winning vs. losing) are tested as moderators of this relationship. In two studies, men and women (total N = 398) competed in the competitive will task (timed weight-holding) either individually or in the presence of an opponent (Study 1) or as a team with and without the presence of a competitor team (Study 2). Results showed a positive relationship between testosterone reactivity and performance for men, particularly those who won or ranked highest among their group - with increasing testosterone predicting better performance and decreasing testosterone predicting worse performance. For women, the effect only emerged among individuals who competed in dyads and lost. In Study 2, an exploratory mediation analysis revealed that individual differences in trait dominance predicted both testosterone reactivity to competition and task performance, with testosterone reactivity (moderated by sex and status outcome) partially explaining the direct relationship between dominance-related traits and behavior. Our goal was to examine testosterone reactivity in relation to real-time competitive effort and highlight the potential role of this relationship in explaining how individual differences in trait dominance produce competitive behavior.

The effects of testosterone on the physiological response to social and somatic stressors

Higher testosterone levels in males have previously been linked to decreased stress reactivity, but in other cases, testosterone has been reported to increase the stress response. We addressed these inconsistencies in a placebo-controlled single-dose testosterone administration study, in which 120 male participants were randomly assigned to undergo a cold-pressor test (CPT, a non-social somatic stressor), a socially evaluated cold-pressor test (SECPT, a social-somatic stressor), or a lukewarm water test (LWT, a non-stressful control condition). Throughout the experiment, blood pressure and interbeat intervals were measured continuously, and saliva samples for hormonal analyses were taken repeatedly at predefined time points. When comparing the groups treated with placebo, the SECPT elicited a larger increase in the systolic blood pressure than CPT, in agreement with previous studies. However, testosterone administration altered this pattern. Compared to placebo, testosterone increased systolic blood pressure during the CPT, whereas the opposite effect was found during the SECPT. Cortisol reactivity was not affected by testosterone administration. The CAG repeat polymorphism of the androgen receptor gene was unrelated to the effects of testosterone on the stress response, but it was correlated with blood pressure across the whole sample. Our findings demonstrate that testosterone's effects on the stress response are dependent on the social context. Testosterone's ability to flexibly influence the response to stressors may be an important mechanism through which the hormone promotes adaptive behavior. Our results are also in line with research showing that testosterone decreases social anxiety and suggest it may help to modulate the effects of stress in socially challenging situations.

The Effects of a Low Calorie Ketogenic Diet on Glycaemic Control Variables in Hyperinsulinemic Overweight/Obese Females

Diet is a factor which can influence both glycaemic variables and body mass. The aim of this study was to compare the influence of a 12-week, well-planned, low-calorie ketogenic diet (LCKD) on hyperglycaemic, hyperinsulinemic and lipid profile in adult, overweight or obese females. Ninety-one females who participated in the study were divided into two groups: a LCKD group who followed a hypocaloric ketogenic diet (8% of carbohydrate, 72% of fat and 20% of proteins) (n = 46), and a control group (CG) (n = 45) who continued their typical diet (50% of carbohydrates, 32% of fat and 18% of proteins). Methods: Baseline and post-intervention glucose (Gl), insulin (I), glycated haemoglobin (HbA1c), Homeostatic model assessment HOMA-IR, triglycerides (TG) and high-density cholesterol (HDL-C) were evaluated. Also, body mass (BM), waist circumference (WC), hip circumference (HC) and thigh circumference (TC) were measured. Results: Compared with the CG, there were significant changes observed in the LCKD group regarding all biochemical variables. Also, BM, TC, WC and AC changed significantly in the LCKD group compared with the CG. Conclusions: The 12-week LCKD intervention changed the glucose control variables, body mass, as well as waist, hip and thigh circumferences. A low-calorie ketogenic diet may be recommended for adult females with glucose control variables disturbance and excess body mass.

Social withdrawal and testosterone levels in early adolescent boys

Social withdrawal may lead to mental health problems and can have a large impact on a life course, particularly among boys. To support adolescents with social withdrawal, an integrative understanding of the biological bases would be helpful. Social dominance, a possible opposite of social withdrawal, is known to have positive associations with testosterone levels. A previous study suggested that social withdrawal has a negative relationship with sexual maturity among adolescent boys. However, the relationship between social withdrawal and testosterone in adolescence is unknown. This study aimed to examine whether social withdrawal was negatively associated with testosterone levels in early adolescent boys. Salivary samples were collected from 159 healthy early adolescent boys (mean age [standard deviation]: 11.5 [0.73]) selected from participants of the "population-neuroscience study of the Tokyo Teen Cohort" (pn-TTC). Social withdrawal and confounding factors, such as the secondary sexual characteristics and their age in months, were evaluated by self-administered questionnaires completed by the primary parents. The degree of social withdrawal was assessed with the Child Behaviour Checklist (CBCL). Levels of salivary testosterone, and cortisol as a control, were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Logistic regression was conducted to examine the association between social withdrawal and testosterone levels. A higher risk of social withdrawal was associated with a lower salivary testosterone level after adjustment for age in months (odds ratio 0.55, 95 % confidence interval 0.33-0.94), and the association remained significant after adjusting for body mass index, the degree of anxiety/depression and pubertal stage. Thus, we found a negative relationship between social withdrawal and testosterone levels in early adolescent boys. These findings may help to clarify the biological foundations of and to develop support for social withdrawal.

Exogenous testosterone increases status-seeking motivation in men with unstable low social status

Testosterone is associated with status-seeking behaviors such as competition, which may depend on whether one wins or loses status, but also on the stability of one's status. We examined (1) to what extent testosterone administration affects competition behavior in repeated social contests in men with high or low rank, and (2), whether this relationship is moderated by hierarchy stability, as predicted by the status instability hypothesis. Using a real effort-based design in healthy male participants (N = 173 males), we first found that testosterone (vs. placebo) increased motivation to compete for status, but only in individuals with an unstable low status. A second part of the experiment, tailored to directly compare stable with unstable hierarchies, indicated that exogenous testosterone again increased competitive motivation in individuals with a low unstable status, but decreased competition behavior in men with low stable status. Additionally, exogenous testosterone increased motivation in those with a stable high status. Further analysis suggested that these effects were moderated by individuals' trait dominance, and genetic differences assessed by the androgen receptor (CAG-repeat) and dopamine transporter (DAT1) polymorphisms. Our study provides evidence that testosterone specifically boosts status-related motivation when there is an opportunity to improve one's social status. The findings contribute to our understanding of testosterone's causal role in status-seeking motivation in competition behavior, and indicate that testosterone adaptively increases our drive for high status in a context-dependent manner. We discuss potential neurobiological pathways through which testosterone may attain these effects on behavior.

The effects of psychosocial stress on intergroup resource allocation

Stress changes our social behavior. Traditionally, stress has been associated with “fight-or-flight” – the tendency to attack an aggressor, or escape the stressor. But stress may also promote the opposite pattern, i.e., “tend-and-befriend” – increased prosociality toward others. It is currently unclear which situational or physiological factors promote one or the other. Here, we hypothesized that stress stimulates both tendencies, but that fight-or-flight is primarily directed against a potentially hostile outgroup, moderated by rapid-acting catecholamines, while tend-and-befriend is mainly shown towards a supportive ingroup, regulated by cortisol. To test this hypothesis, we measured stress-related neurohormonal modulators and sex hormones in male and female participants who were exposed to a psychosocial stressor, and subsequently played an intergroup social dilemma game in which they could reveal prosocial motives towards an ingroup (ingroup-love) and hostility towards an outgroup (outgroup-hate). We found no significant effects of stress on social preferences, but stress-related heart-rate increases predicted outgroup-hostile behavior. Furthermore, when controlling for testosterone, cortisol was associated with increased ingroup-love. Other-regarding behavior was overall higher in male than female participants. Our mixed results are of interest to scholars of the effects of stress on prosocial and aggressive behavior, but call for refinement in future replications.

The role of personality, cognition, and affective state in same-sex contests in the red junglefowl

Abstract

Intra-species contests are common in the animal kingdom and can have fitness consequences. Most research on what predicts contest outcome focuses on morphology, although differences in personality and cognition may also be involved. Supporting this, more proactive individuals often have dominant status, although the causality of this relationship is rarely investigated. Contest initiators often win; thus, individuals that are more proactive in their personality (e.g., more aggressive, risk-taking) or cognition (e.g., more optimistic, impulsive) may initiate contests more often. To investigate this, we assayed the behavior and cognition of sexually mature male and female red junglefowl (Gallus gallus), a species in which both sexes contest over social status, before staging intra-sexual contests. We confirm that contest initiators were more likely to win. In males, individuals that behaved more boldly in a novel arena test were more likely to initiate and win contests. Female initiators tended to be less active in novel object test, more aggressive in a restrained opponent test, and respond less optimistically in a cognitive judgement bias test, whereas the main predictor of whether a female would win a contest was whether she initiated it. These results suggest that behaviors attributed to proactive and reactive personalities, and—at least for female red junglefowl—optimism, can affect contest initiation and outcome. Therefore, within species, and depending on sex, different aspects of behavior and cognition may independently affect contest initiation and outcome. The generality of these findings, and their fitness consequences, requires further investigation.

Significance statement

In red junglefowl, we explored how behavior previously shown to describe personality, cognition, and affective state affected initiation and outcome of intra-sexual contests, by staging contests between sexually mature individuals previously assayed in behavioral and cognitive tests. In both sexes, contest initiators usually won. Bolder males were more likely to initiate and win contests. Female contests initiators were less active, more aggressive, and less optimistic. Our results suggest that personality and cognition could affect the initiation and outcome of contests and that how this occurs may differ between sexes.

Human social neuroendocrinology: Review of the rapid effects of testosterone

Contribution to Special Issue on Fast effects of steroids. It is well documented that testosterone concentrations change rapidly within reproductively relevant contexts (e.g., competition, mate-seeking). It has been argued that such rapid changes in testosterone may serve to adaptively fine-tune ongoing and/or future social behaviour according to one's social environment. In this paper, we review human correlational and experimental evidence suggesting that testosterone fluctuates rapidly in response to competition and mate-seeking cues, and that such acute changes may serve to modulate ongoing and/or future social behaviours (e.g., risk-taking, competitiveness, mate-seeking, and aggression). Some methodological details, which limit interpretation of some of this human work, are also discussed. We conclude with a new integrative model of testosterone secretion and behaviour, the Fitness Model of Testosterone Dynamics. Although we focus primarily on human aggression in this review, we also highlight research on risk-taking, competitiveness, and mate-seeking behaviour.

On the Drive Specificity of Freudian Drives for the Generation of SEEKING Activities: The Importance of the Underestimated Imperative Motor Factor

Doubters of Freud's theory of drives frequently mentioned that his approach is outdated and therefore cannot be useful for solving current problems in patients with mental disorders. At present, many scientists believe that affects rather than drives are of utmost importance for the emotional life and the theoretical framework of affective neuroscience, developed by Panksepp, strongly underpinned this view. Panksepp evaluated seven so-called command systems and the SEEKING system is therein of central importance. Panksepp used Pankseppian drives as inputs for the SEEKING system but noted the missing explanation of drive-specific generation of SEEKING activities in his description. Drive specificity requires dual action of the drive: the activation of a drive-specific brain area and the release of the neurotransmitter dopamine. Noticeably, as Freud claimed drive specificity too, it was here analyzed whether a Freudian drive can evoke the generation of drive-specific SEEKING activities. Special importance was addressed to the imperative motor factor in Freud's drive theory because Panksepp's formulations focused on neural pathways without specifying underlying neurotransmitter/endocrine factors impelling motor activity. As Panksepp claimed sleep as a Pankseppian drive, we firstly had to classified sleep as a Freudian drive by using three evaluated criteria for a Freudian drive. After that it was possible to identify the imperative motor factors of hunger, thirst, sex, and sleep. Most importantly, all of these imperative motor factors can both activate a drive-specific brain area and release dopamine from dopaminergic neurons, i.e., they can achieve the so-called drive specificity. Surprisingly, an impaired Freudian drive can alter via endocrinological pathways the concentration of the imperative motor factor of a second Freudian drive, obviously in some independence to the level of the metabolic deficit, thereby offering the possibility to modulate the generation of SEEKING activities of this second Freudian drive. This novel possibility might help to refine the general understanding of the action of Freudian drives. As only imperative motor factors of Freudian drives can guarantee drive specificity for the generation of SEEKING activities, the impact of Freud's construct Eros (with its constituents hunger, thirst, sex, and sleep) should be revisited.

Estrogen Interactions With Lipid Rafts Related to Neuroprotection. Impact of Brain Ageing and Menopause

Estrogens (E2) exert a plethora of neuroprotective actions against aged-associated brain diseases, including Alzheimer's disease (AD). Part of these actions takes place through binding to estrogen receptors (ER) embedded in signalosomes, where numerous signaling proteins are clustered. Signalosomes are preferentially located in lipid rafts which are dynamic membrane microstructures characterized by a peculiar lipid composition enriched in gangliosides, saturated fatty acids, cholesterol, and sphingolipids. Rapid E2 interactions with ER-related signalosomes appear to trigger intracellular signaling ultimately leading to the activation of molecular mechanisms against AD. We have previously observed that the reduction of E2 blood levels occurring during menopause induced disruption of ER-signalosomes at frontal cortical brain areas. These molecular changes may reduce neuronal protection activities, as similar ER signalosome derangements were observed in AD brains. The molecular impairments may be associated with changes in the lipid composition of lipid rafts observed in neurons during menopause and AD. These evidences indicate that the changes in lipid raft structure during aging may be at the basis of alterations in the activity of ER and other neuroprotective proteins integrated in these membrane microstructures. Moreover, E2 is a homeostatic modulator of lipid rafts. Recent work has pointed to this relevant aspect of E2 activity to preserve brain integrity, through mechanisms affecting lipid uptake and local biosynthesis in the brain. Some evidences have demonstrated that estrogens and the docosahexaenoic acid (DHA) exert synergistic effects to stabilize brain lipid matrix. DHA is essential to enhance molecular fluidity at the plasma membrane, promoting functional macromolecular interactions in signaling platforms. In support of this, DHA detriment in neuronal lipid rafts has been associated with the most common age-associated neuropathologies, namely AD and Parkinson disease. Altogether, these findings indicate that E2 may participate in brain preservation through a dual membrane-related mechanism. On the one hand, E2 interacting with ER related signalosomes may protect against neurotoxic insults. On the other hand, E2 may exert lipostatic actions to preserve lipid balance in neuronal membrane microdomains. The different aspects of the emerging multifunctional role of estrogens in membrane-related signalosomes will be discussed in this review.

Testosterone and androgen receptor gene polymorphism are associated with confidence and competitiveness in men

A contribution to a special issue on Hormones and Human Competition. Studies in non-human animals and humans have demonstrated the important role of testosterone in competitive interactions. Here, we investigated whether endogenous testosterone levels predict the decision to compete, in a design excluding spite as a motive underlying competitiveness. In a laboratory experiment with real monetary incentives, 181 men solved arithmetic problems, first under a noncompetitive piece rate, followed by a competition incentive scheme. We also assessed several parameters relevant to competition, such as risk taking, performance, and confidence in one's own performance. Salivary testosterone levels were measured before and 20min after the competition task using mass spectrometry. Participants were also genotyped for the CAG repeat polymorphism of the androgen receptor gene, known to influence the efficacy of testosterone signaling in a reciprocal relationship to the number of CAG repeats. We observed a significant positive association between basal testosterone levels and the decision to compete, and that higher testosterone levels were related to greater confidence in one's own performance. Whereas the number of CAG repeats was not associated with the choice to compete, a lower number of CAG repeats was related to greater confidence in those who chose to compete, but this effect was attributable to the polymorphism's effect on actual performance. An increase in testosterone levels was observed following the experiment, and this increase varied with self-reported high-school math grades. We expand upon the latest research by documenting effects of the androgen system in confidence in one's own ability, and conclude that testosterone promotes competitiveness without spite.

A benefit-cost framework of motivation for a specific activity

How can an individual be motivated to perform a target exercise or activity? This question arises in training, therapeutic, and education settings alike, yet despite-or even because of-the large range of extant motivation theories, finding a clear answer to this question can be challenging. Here we propose an application-friendly framework of motivation for a specific activity or exercise that incorporates core concepts from several well-regarded psychological and economic theories of motivation. The key assumption of this framework is that motivation for performing a given activity is determined by the expected benefits and the expected costs of (performance of) the activity. Benefits comprise positive feelings, gains, and rewards experienced during performance of the activity (intrinsic benefits) or achieved through the activity (extrinsic benefits). Costs entail effort requirements, time demands, and other expenditure (intrinsic costs) as well as unwanted associated outcomes and missing out on alternative activities (extrinsic costs). The expected benefits and costs of a given exercise are subjective and state dependent. We discuss convergence of the proposed framework with a selection of extant motivation theories and briefly outline neurobiological correlates of its main components and assumptions. One particular strength of our framework is that it allows to specify five pathways to increasing motivation for a target exercise, which we illustrate and discuss with reference to previous empirical data.