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Developmental Effects (developmental + effects)
Selected AbstractsGrowth curve analyses are best suited to examine the relation between developmental pathways and selective breeding: Comment on Hofer, Shair, Masmela, & Brunelli, "Developmental effects of selective breeding for an infantile trait: The rat pup ultrasonic isolation call"DEVELOPMENTAL PSYCHOBIOLOGY, Issue 4 2001George F. Michel Abstract Hofer, Brunelli, Shair, & Masmela (2001) provide valuable information about the effects of selective breeding on rat-pup behaviors and physiology. Although the design and statistical analytic techniques employed are typical of those used to evaluate behavioral development in animals, I offer several suggestions about how to evaluate the influence of selective breeding on developmental pathways using modern statistical techniques. As Hofer et al. demonstrate, the development of rat behavior and physiology can be an excellent model for examining the relation between selection and development. © 2001 John Wiley & Sons, Inc. Dev Psychobiol 39: 247,250, 2001 [source] Letter to the editor: Chronicle for an orphan trait: Comment on Hofer, Shair, Masmela, & Brunelli, "Developmental effects of selective breeding for an infantile trait: The rat pup ultrasonic isolation call"DEVELOPMENTAL PSYCHOBIOLOGY, Issue 4 2001Pierre L. Roubertoux Abstract Hofer, Brunelli, Shair, and Masmela (2001) examined several behavioral and physiological measures in low, high, and unselected lines obtained from a divergent selection for ultrasound production (USP) in young rats. Although the response to selection was clear-cut, few correlated responses appeared. This surprising result could be explained by two reasons. USP has polygenic correlates in this population, and most of the chromosomal regions that are linked with these measures only contribute to a small part of the genetic variance. Therefore, correlated responses to selection might exist, but the common genetic variance between the trait under selection and the indirectly selected trait is too small to be detected by a selective breeding strategy. © 2001 John Wiley & Sons, Inc. Dev Psychobiol 39: 251,254, 2001.. [source] Developmental effects of bioaccumulated selenium in eggs and larvae of two salmonid speciesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2005Jodi Holm Abstract Elevated concentrations of Se have been detected in cold, flowing water habitats near uranium and coal mines in Canada. Fish from these systems have concentrations of Se in their tissues that exceed toxic effect thresholds that have been established for warm-water fishes. However, the applicability of toxic effect thresholds and guidelines to cold water, lotic habitats is a matter of contention in the literature since most cases of Se toxicosis have been documented in standing, warm-water systems. To examine the possibility of impaired reproduction in wild rainbow trout (Oncorhynchus mykiss) and brook trout (Salvelinus fontinalis) near coal mining activity in the northeastern slopes region of Alberta, Canada, spawn from both species were collected from exposure and reference sites. Gametes were fertilized in the laboratory, reared to the swim-up stage, and examined for deformities. A significant relationship was observed for rainbow trout between the amount of Se in eggs and the incidence of developmental abnormalities, specifically craniofacial defects, skeletal deformities, and edema. These associations approximate exponential functions with probabilities that 15% of the population would be affected occurring between 8.8 and 10.5 ,g Se per gram of wet egg weight, based on probit analysis. These relationships are similar to those described for centrarchids inhabiting a seleniferous warm-water lake. No such relationships were established for brook trout. [source] Ecdysteroid synthesis and imaginal disc development in the midge Chironomus riparius as biomarkers for endocrine effects of tributyltinENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2002Torsten Hahn Abstract Acute effects of the endocrine disruptor bis (tri- n -butyltin) oxide (TBTO) on molting-hormone biosynthesis and imaginaldisc development were investigated in larvae of the midge Chironomus riparius (Meigen). Ecdysteroid synthesis was measured by 24-h incubation of molting-hormone-synthesizing tissues (prothoracic glands) in vitro with or without the addition of TBTO. The amount of ecdysteroids produced was analyzed by radioimmunoassay. Developmental effects in vivo were investigated by determining the developmental phase of the genital imaginal discs before and after a 48-h exposure to TBTO in water. Sex-specific effects were found with both endpoints. Ecdysteroid synthesis was significantly reduced (analysis of variance [ANOVA], p , 0.005) in female larvae at all concentrations (TBTO-Sn at 50, 500, and 5,000 ng/L), whereas a significant elevation of the biosynthesis rate occurred in male larvae in the 500-ng/L treatment (ANOVA, p , 0.05). In vivo experiments with development of the genital imaginal disc within a 48-h exposure period revealed a significantly slower development in female larvae and a significantly faster development in male larvae (contingency tables, p , 0.001) at all concentrations tested (TBTO-Sn at 10, 50, 200, and 1,000 ng/L). These results partly coincided with the in vitro effects on molting-hormone synthesis. The 48-h median lethal concentration (LC50) was 25 ,g/L (20,30 ,g/L 95% confidence intervals). The combination of in vitro and in vivo methods has proven to be a useful approach for the detection of endocrine effects of TBTO in C. riparius at levels 2,000-fold below the LC50 value. High sensitivity and short test duration suggest that chironomids may have potential as freshwater sentinel organisms for endocrine-disrupting chemicals. [source] Developmental effects of physiologically weak electric fields and heat: An overview,BIOELECTROMAGNETICS, Issue S7 2005Richard D. Saunders Abstract This study summarizes the possible effects on prenatal development of physiologically weak electric fields induced in the body by exposure to extremely low frequency (ELF) electromagnetic fields and of elevated temperature levels that might result from exposure to radiofrequency (RF) radiation. Both topics have been discussed at recent international workshops organized by WHO in collaboration with other bodies. Mammalian development is characterized by a highly ordered sequence of cell proliferation and differentiation, migration, and programmed cell death. These processes, particularly proliferation and migration, are susceptible to a variety of environmental agents including raised maternal temperature. In addition, there is growing evidence that physiologically weak endogenous DC electric fields and ionic currents have a role in guiding developmental processes, including cell orientation and migration, by establishing electrical potential gradients. Disruption of these fields can adversely affect development in amphibian and bird embryos, which are experimentally accessible, and may well do so in mammalian embryos. The extent to which induced ELF electric fields might influence these and other processes that take place during prenatal development, childhood, and adolescence is less clear. Organogenesis, which takes place primarily during the embryonic period, is susceptible to raised maternal temperatures; a large number of studies have shown that RF exposure produces developmental effects that can be attributed to heat. The development of the central nervous system is particularly susceptible to raised temperatures; a reduction in brain size, which results in a smaller head, is one of the most sensitive markers of heat-induced developmental abnormalities and can be correlated with heat-induced behavioral deficits. However, some aspects of CNS development have been less well explored, particularly effects on corticogenesis. In addition, the persistence of CNS developmental sensitivity through to childhood and adolescence is not clear. Bioelectromagnetics Supplement 7:S127,S132, 2005. © 2005 Wiley-Liss, Inc. [source] An Eye for Detail: An Event-Related Potential Study of the Rapid Processing of Fearful Facial Expressions in ChildrenCHILD DEVELOPMENT, Issue 4 2010Petra H. J. M. Vlamings There is converging evidence for the presence of a fast subcortical face-processing route that operates on global face characteristics in the mature brain. Until now, little has been known about the development of such a route, which is surprising given suggestions that this fast subcortical face-processing route might be affected in neurodevelopmental disorders such as autism. To address this, early visual event-related potentials to pictures of fearful and neutral faces containing detailed or global information in 3- to 4-year-old (n = 20), 5- to 6-year-old (n = 25), and 7- to 8-year-old (n = 25) children were compared. In children, emotional processing was driven by detailed information. Developmental effects are discussed in terms of maturation of the fast subcortical face-processing route as well as an increase in experience with facial expressions with age. [source] Pharmacogenetics of the neurodevelopmental impact of anticancer chemotherapyDEVELOPMENTAL DISABILITIES RESEARCH REVIEW, Issue 3 2008Philippe Robaey Abstract Pharmacogenetics holds the promise of minimizing adverse neurodevelopmental outcomes of cancer patients by identifying patients at risk, enabling the individualization of treatment and the planning of close follow-up and early remediation. This review focuses first on methotrexate, a drug often implicated in neurotoxicity, especially when used in combination with brain irradiation. The second focus is on glucocorticoids that have been found to be linked to adverse developmental effects in relation with the psychosocial environment. For both examples, we review how polymorphisms of genes encoding enzymes involved in specific mechanisms of action could moderate adverse neurodevelopmental consequences, eventually through common final pathways such as oxidative stress. We discuss a multiple hit model and possible strategies required to rise to the challenge of this integrative research. © 2008 Wiley-Liss, Inc. Dev Disabil Res Rev 2008;14:211,220. [source] Maternal behavior changes after immune challenge of neonates with developmental effects on adult social behaviorDEVELOPMENTAL PSYCHOBIOLOGY, Issue 1 2003Kathryn E. Hood Abstract To examine whether maternal responsiveness during interactions with endotoxin-treated pups contributes to long-term effects on social development, neonatal mice were fostered on postnatal day 1 to dams from three selectively bred lines that differ in social behaviors. On day 5, neonates were administered saline or 0.5 mg/kg endotoxin (lipopolysaccharide, i.p.). Observations of undisturbed dams and litters on days 2, 4, 6, and 8 showed modest line differences in maternal behaviors. At the peak intensity of the transient illness induced by endotoxin (3 hr postinjection on day 5), dams increased licking and decreased time off-nest for endotoxin, but not saline-treated pups. As adults, fostered-reared males were observed in brief social interactions. Males exposed to endotoxin early in life showed changes in adult social behaviors that depended on foster dam line as well as individual differences in maternal responsiveness. Maternal responsiveness to stressed neonates can ameliorate the social,developmental effects of early illness. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 42: 17,34, 2003. [source] Effects of bisphenol A and tetrabromobisphenol A on sex organ development in quail and chicken embryosENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2001Cecilia Berg Abstract The plastic monomere bisphenol A (BPA) and the flame retardant tetrabromobisphenol A (TBBPA) were examined for estrogen-like developmental effects on the reproductive organs in avian embryos. The synthetic estrogen diethylstilbestrol (DES) was used as a positive control. The test compounds were injected into the yolk of quail and chicken eggs early during incubation and the embryos were examined 2 d before anticipated hatching. At 200 ,g/g egg, BPA induced Müllerian duct (embryonic oviduct) malformation in female quail embryos and feminization of the left testis (ovotestis) in male chicken embryos. The estrogenic potency of BPA compared with DES was species and endpoint specific. Müllerian duct malformation was the most sensitive endpoint in quail embryos, whereas ovotestis formation was the most sensitive response in chicken embryos. Tetrabromobisphenol A caused high embryo mortality at 45 ,g/g egg in both species, but no estrogen-like effects were observed. Bisphenol A caused mortality only in chicken embryos at 67 and 200 ,g/g egg. To our knowledge, this is the first report on estrogen-like or embryolethal effects of BPA and TBBPA in birds. [source] Developmental changes in the BDNF-induced modulation of inhibitory synaptic transmission in the Kölliker,Fuse nucleus of ratEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2007Miriam Kron Abstract The Kölliker,Fuse nucleus (KF), part of the pontine respiratory group, is involved in the control of respiratory phase duration, and receives both excitatory and inhibitory afferent input from various other brain regions. There is evidence for developmental changes in the modulation of excitatory inputs to the KF by the neurotrophin brain-derived neurotrophic factor (BDNF). In the present study we investigated if BDNF exerts developmental effects on inhibitory synaptic transmission in the KF. Recordings of inhibitory postsynaptic currents (IPSCs) in KF neurons in a pontine slice preparation revealed general developmental changes. Recording of spontaneous and evoked IPSCs (sIPSCs, eIPSCS) revealed that neonatally the ,-aminobutyric acid (GABA)ergic fraction of IPSCs was predominant, while in later developmental stages glycinergic neurotransmission significantly increased. Bath-application of BDNF significantly reduced sIPSC frequency in all developmental stages, while BDNF-mediated modulation on eIPSCs showed developmental differences. The eIPSCs mean amplitude was uniformly and significantly reduced following BDNF application only in neurons from rats younger than postnatal day 10. At later postnatal stages the response pattern became heterogeneous, and both augmentations and reductions of eIPSC amplitudes occurred. All BDNF effects on eIPSCs and sIPSCs were reversed with the tyrosine kinase receptor-B inhibitor K252a. We conclude that developmental changes in inhibitory neurotransmission, including the BDNF-mediated modulation of eIPSCs, relate to the postnatal maturation of the KF. The changes in BDNF-mediated modulation of IPSCs in the KF may have strong implications for developmental changes in synaptic plasticity and the adaptation of the breathing pattern to afferent inputs. [source] PERSPECTIVE: EVOLUTIONARY DEVELOPMENTAL BIOLOGY AND THE PROBLEM OF VARIATIONEVOLUTION, Issue 4 2000David L. Stern Abstract. One of the oldest problems in evolutionary biology remains largely unsolved. Which mutations generate evolutionarily relevant phenotypic variation? What kinds of molecular changes do they entail? What are the phenotypic magnitudes, frequencies of origin, and pleiotropic effects of such mutations? How is the genome constructed to allow the observed abundance of phenotypic diversity? Historically, the neo-Darwinian synthesizers stressed the predominance of micromutations in evolution, whereas others noted the similarities between some dramatic mutations and evolutionary transitions to argue for macromutationism. Arguments on both sides have been biased by misconceptions of the developmental effects of mutations. For example, the traditional view that mutations of important developmental genes always have large pleiotropic effects can now be seen to be a conclusion drawn from observations of a small class of mutations with dramatic effects. It is possible that some mutations, for example, those in cis -regulatory DNA, have few or no pleiotropic effects and may be the predominant source of morphological evolution. In contrast, mutations causing dramatic phenotypic effects, although superficially similar to hypothesized evolutionary transitions, are unlikely to fairly represent the true path of evolution. Recent developmental studies of gene function provide a new way of conceptualizing and studying variation that contrasts with the traditional genetic view that was incorporated into neo-Darwinian theory and population genetics. This new approach in developmental biology is as important for micro-evolutionary studies as the actual results from recent evolutionary developmental studies. In particular, this approach will assist in the task of identifying the specific mutations generating phenotypic variation and elucidating how they alter gene function. These data will provide the current missing link between molecular and phenotypic variation in natural populations. [source] A tale of two ,globalizations': capital flows from rich to poor in two eras of global financeINTERNATIONAL JOURNAL OF FINANCE & ECONOMICS, Issue 4 2006Moritz Schularick Abstract In this paper we take a comparative look at the patterns of capital flows from rich to poor countries in two eras of financial globalization. The paper extends recent research on the developmental effects of international financial integration, long-term trends in capital mobility and ,globalization in historical perspective'. Analysing the patterns of international financial integration in the three decades of the classical gold standard and after 1990 we show that investment in developing countries was a central element of 19th century financial globalization, but plays only a minor role today. The Lucas paradox of capital failing to flow from rich to poor has grown much stronger. In historical perspective, today's financial globalization is marked by massive diversification flows between high-income economies and a relative marginalization of less-developed economies. Copyright © 2006 John Wiley & Sons, Ltd. [source] In Three Brain Regions Central to Maternal Behaviour, Neither Male Nor Female Phodopus Dwarf Hamsters Show Changes in Oestrogen Receptor Alpha Distribution with Mating or ParenthoodJOURNAL OF NEUROENDOCRINOLOGY, Issue 12 2008M. E. Timonin Oestrogen receptor (ER), immunoreactivity in three brain regions relevant to maternal behaviour (medial preoptic area, bed nucleus of the stria terminalis and medial amygdala) was measured in two species of dwarf hamster that both mate during a postpartum oestrous but differ in expression of paternal behaviour. Male and female Phodopus campbelli and Phodopus sungorus were sampled as sexually naïve adults, following mating to satiety, and as new parents. In all brain regions, females expressed higher levels of ER, than males. Species did not have an effect on ER, distribution except in the medial amygdala, where P. sungorus females had higher expression levels than all other groups. Behavioural status was not associated with altered ER, expression. These results were not expected for females and suggest that a primary activational role for oestrogen, acting through ER, in these regions, does not generalise to maternal behaviour in Phodopus. In males, these results are consistent with previous manipulations of the ER, ligand, oestrogen, and suggest that paternal behaviour in P. campbelli is likely to be regulated by developmental effects of oestrogen on the brain during early life (similar to Microtus ochrogaster), rather than through activation by oestrogen at the time of fatherhood (similar to Peromyscus californicus). [source] Urinary chemosignals in giant pandas (Ailuropoda melanoleuca): seasonal and developmental effects on signal discriminationJOURNAL OF ZOOLOGY, Issue 3 2004A. M. White Abstract As a solitary species, giant pandas Ailuropoda melanoleuca have a chemical communication system that allows for avoidance with conspecifics throughout most of the year and facilitates breeding during their brief reproductive period. To date, most studies have focused on adults during the breeding season, but much remains to be learned about developmental and seasonal effects on chemical communication. Here, using odour discrimination methodology, we examine these contextual influences on chemosignalling in giant pandas for the first time. During the breeding season both adult and subadult giant pandas overtly discriminated conspecific sex using chemical cues in urine. Male urine was consistently investigated more than female urine by pandas across all age-sex categories. This preference for male urine was observed for both adult and subadult urine donors, indicating that adult levels of reproductive hormones are not necessary for the production of sex-specific urinary odour cues. By contrast, giant pandas did not overtly discriminate sex during the non-breeding season. This finding underscores that negative results for discrimination studies need to be interpreted with caution, as many contextual factors may influence overt expression of this ability. Evidence points to seasonal changes in motivation, rather than in the availability of sex-specific chemical cues in urine, as the causal factor for changing odour discrimination patterns. These and other findings are discussed in the light of the potential role that discrimination of odour plays in the regulation of competitive and reproductive interactions in nature. [source] Emanuel Miller Lecture Developmental Risks (Still) Associated with Early Child CareTHE JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY AND ALLIED DISCIPLINES, Issue 7 2001Jay Belsky In the mid to late 1980s a major controversy erupted when Belsky's (1986, 1988, 1990) analysis of research produced the conclusion that early and extensive nonmaternal care carried risks in terms of increasing the probability of insecure infant-parent attachment relationships and promoting aggression and noncompliance during the toddler, preschool, and early primary school years. Widespread critiques of Belsky's analysis called attention to problems associated with the Strange Situation procedure for measuring attachment security in the case of day-care reared children and to the failure of much of the cited research to take into consideration child-care quality and control for background factors likely to make children with varying child-care experiences developmentally different in the first place. In this lecture, research concerning the developmental effects of child care and maternal employment initiated in the first year of life that has emerged since the controversy broke is reviewed. Evidence indicating that early, extensive, and continuous nonmaternal care is associated with less harmonious parent-child relations and elevated levels of aggression and noncompliance suggests that concerns raised about early and extensive child care 15 years ago remain valid and that alternative explanations of Belsky's originally controversial conclusion do not account for seemingly adverse effects of routine nonmaternal care that continue to be reported in the literature. [source] Diversification and co-option of RAD-like genes in the evolution of floral asymmetryTHE PLANT JOURNAL, Issue 1 2007Catherine E. L. Baxter Summary To understand how changes in gene regulatory networks lead to novel morphologies, we have analysed the evolution of a key target gene, RAD, controlling floral asymmetry. In Antirrhinum, flower asymmetry depends on activation of RAD in dorsal regions of the floral meristem by the upstream regulators CYC and DICH. We show that Arabidopsis, a species with radially symmetric flowers, contains six RAD -like genes, reflecting at least three duplications since the divergence of Antirrhinum and Arabidopsis. Unlike the situation in Antirrhinum, none of the Arabidopsis RAD -like genes are activated in dorsal regions of the flower meristem. Rather, the RAD -like genes are expressed in distinctive domains along radial or ab-adaxial axes, consistent with a range of developmental roles. Introduction of a RAD genomic clone from Antirrhinum into Arabidopsis leads to a novel expression pattern that is distinct from the expression pattern of RAD in Antirrhinum and from the endogenous RAD -like genes of Arabidopsis. Nevertheless, RAD is able to influence developmental targets in Arabidopsis, as ectopic expression of RAD has developmental effects in this species. Taken together, our results suggest that duplication and divergence of RAD -like genes has involved a range of cis- and trans- regulatory changes. It is possible that such changes led to the coupling of RAD to CYC regulation in the Antirrhinum lineage and hence the co-option of RAD had a role in the generation of flower dorsoventral asymmetry. [source] Getting the problem of endocrine disruption into focus: The need for a pause for thoughtAPMIS, Issue 12 2000JOHN ASHBY The study of chemically-induced endocrine disruption in mammals is a relatively new field of endeavour, and it has been assailed by an unusual level of disagreement among investigators regarding the developmental effects produced by chemicals in animals. This article discusses the several sources of uncertainty in endocrine toxicity studies, and the intrinsic variability of many of the key experimental parameters. It is concluded that current uncertainties are due to the absence of an extensive agreed control database for the developmental parameters under study, coupled to the established intrinsic variability of these parameters between strains/species of test animals and test protocols. Only when these factors are generally accepted and well studied will it be possible to design studies capable of distinguishing the possible subtle endocrine toxicity of chemicals and chance observations that cannot be independently reproduced. [source] Organotin levels in the Ria Formosa lagoon, PortugalAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 7 2002M. R. Coelho Abstract Organotin concentrations were measured in water, sediments and clams (Ruditapes decussatus) from 11 sites in the Ria Formosa lagoon, Portugal, in 1992,93. Results showed a marked spatial pattern of tributyltin (TBT) and dibutyltin concentrations. The highest organotin concentrations were observed at Olhão (site 5), where the most important fishing harbour of the Southern coast of Portugal is located. Results indicated that fishing vessels, moored in the harbour at Olhão (site 5), were the major source of organotin contamination to the lagoon. No significant seasonal trend was observed, suggesting a continuous input of organotin compounds throughout the year. In several areas of the lagoon the TBT burdens in R. decussatus could have deleterious developmental effects. Copyright © 2002 John Wiley & Sons, Ltd. [source] Developmental effects of physiologically weak electric fields and heat: An overview,BIOELECTROMAGNETICS, Issue S7 2005Richard D. Saunders Abstract This study summarizes the possible effects on prenatal development of physiologically weak electric fields induced in the body by exposure to extremely low frequency (ELF) electromagnetic fields and of elevated temperature levels that might result from exposure to radiofrequency (RF) radiation. Both topics have been discussed at recent international workshops organized by WHO in collaboration with other bodies. Mammalian development is characterized by a highly ordered sequence of cell proliferation and differentiation, migration, and programmed cell death. These processes, particularly proliferation and migration, are susceptible to a variety of environmental agents including raised maternal temperature. In addition, there is growing evidence that physiologically weak endogenous DC electric fields and ionic currents have a role in guiding developmental processes, including cell orientation and migration, by establishing electrical potential gradients. Disruption of these fields can adversely affect development in amphibian and bird embryos, which are experimentally accessible, and may well do so in mammalian embryos. The extent to which induced ELF electric fields might influence these and other processes that take place during prenatal development, childhood, and adolescence is less clear. Organogenesis, which takes place primarily during the embryonic period, is susceptible to raised maternal temperatures; a large number of studies have shown that RF exposure produces developmental effects that can be attributed to heat. The development of the central nervous system is particularly susceptible to raised temperatures; a reduction in brain size, which results in a smaller head, is one of the most sensitive markers of heat-induced developmental abnormalities and can be correlated with heat-induced behavioral deficits. However, some aspects of CNS development have been less well explored, particularly effects on corticogenesis. In addition, the persistence of CNS developmental sensitivity through to childhood and adolescence is not clear. Bioelectromagnetics Supplement 7:S127,S132, 2005. © 2005 Wiley-Liss, Inc. [source] Activational effects of sex hormones on cognition in menCLINICAL ENDOCRINOLOGY, Issue 5 2009A. Ulubaev Summary Background, Changing world demographic patterns, such as the increasing number of older people and the growing prevalence of cognitive impairment, present serious obstacles to preserving the quality of life and productivity of individuals. The severity of dementia varies from subclinical, mild cognitive impairment to neurodegenerative diseases such as Alzheimer's. In normally ageing men, these age-related cognitive declines are accompanied by gradual but marked decreases in androgen levels and changes in other hormone profiles. While developmental effects of sex hormones on cognition in the pre- and early postnatal period have been demonstrated, their activational effects in later life are still a focus of contemporary research. Although there is a plethora of published research on the topic, results have been inconsistent with different studies reporting positive, negative or no effects of sex hormones on various aspects of mental agility. Methods, This review summarizes the evidence supporting the biological plausibility of the activational effects of sex hormones upon cognition and describes the mechanisms of their actions. It offers a comprehensive summary of the studies of the effects of sex hormones on fluid intelligence in men utilizing elements from the Cochrane Collaboration Guidelines for Reviews. The results of both observational (cross-sectional and longitudinal) and interventional studies published to date are collated in table form and further discussed in the text. Factors contributing to the difficulties in understanding the effects of sex hormones on cognition are also examined. Conclusions, Although there is convincing evidence that steroid sex hormones play an organizational role in brain development in men, the evidence for activational effects of sex hormones affecting cognition in healthy men throughout adult life remains inconsistent. To address this issue, a new multifactorial approach is proposed which takes into account the status of other elements of the sex hormones axis including receptors, enzymes and other hormones. [source] | |||||||||||||||||||