We present converging evidence demonstrating poor reliability of task-fMRI measures

What Is the Test-Retest Reliability of Common Task-Functional MRI Measures? New Empirical Evidence and a Meta-Analysis. Maxwell L. Elliott et al. Psychological Science, June 3, 2020. https://doi.org/10.1177/0956797620916786

Abstract: Identifying brain biomarkers of disease risk is a growing priority in neuroscience. The ability to identify meaningful biomarkers is limited by measurement reliability; unreliable measures are unsuitable for predicting clinical outcomes. Measuring brain activity using task functional MRI (fMRI) is a major focus of biomarker development; however, the reliability of task fMRI has not been systematically evaluated. We present converging evidence demonstrating poor reliability of task-fMRI measures. First, a meta-analysis of 90 experiments (N = 1,008) revealed poor overall reliability—mean intraclass correlation coefficient (ICC) = .397. Second, the test-retest reliabilities of activity in a priori regions of interest across 11 common fMRI tasks collected by the Human Connectome Project (N = 45) and the Dunedin Study (N = 20) were poor (ICCs = .067–.485). Collectively, these findings demonstrate that common task-fMRI measures are not currently suitable for brain biomarker discovery or for individual-differences research. We review how this state of affairs came to be and highlight avenues for improving task-fMRI reliability.

Keywords: neuroimaging, individual differences, statistical analysis, cognitive neuroscience

Japanese macaques: Some adult females mount adult males in the context of heterosexual consortships; this research has implications for the evolution of non-conceptive sex in primates

Is female-male mounting functional? An analysis of the temporal patterns of sexual behaviors in Japanese macaques. Noëlle Gunst et al. Physiology & Behavior, June 3 2020, 112983. https://doi.org/10.1016/j.physbeh.2020.112983

Highlights
• Behavioral structure contributes to testing hypotheses about behavioral function
• Temporal analysis of mating sequences helps test the function of female-male mounts
• Female-male mounting may be a sexual solicitation in Japanese monkeys
• Female-male mounting may be a sexual adaptation in Japanese monkeys
• Our research has implications for the evolution of non-conceptive sex in primates

Abstract: In certain populations of Japanese macaques, adult females mount adult males in the context of heterosexual consortships (i.e., temporary but exclusive sexual associations between a male and a female). Previous research suggested that, in this primate species, female-male mounting (FMM) may be a behavioral adaptation. This functional hypothesis holds that FMM is a (special) courtship behaviour, or a (super) sexual solicitation, that serves the function of focusing the male's attention, preventing him from moving away, and expediting male-female mounting, in the context of high female competition for male mates. In this study, we aimed to test some of the proposed functional features of FMM in Japanese macaques by comparing the temporal structure of mating behavioral sequences, including various well-known sexual solicitations, exhibited during heterosexual consortships with and without FMM. To identify and compare recurring series of behavioral events within and across sequences, we used a temporal analysis known as “T-pattern detection and analysis”. Our results (partly) supported the “FMM as a (super) sexual solicitation” hypotheses, and supported the “FMM as a sexual adaptation” hypothesis. The utilization of TPA allows for the detection of hidden features of primates’ behaviors otherwise undetectable by using conventional quantitative approaches, such as the calculation of frequencies or durations of isolated behavioral components, disjointed from the comprehensive behavioral architecture. This study fits into the scheme of a broader investigation of the functionality of non-conceptive mounting patterns observed in Japanese macaques and a reconstruction of their evolutionary history.

Keywords: Structure-functionTemporal structureT-pattern analysisNon-conceptive sexAdaptationEvolutionary by-product

Sperm sex ratio adjustment in a mammal: perceived male competition leads to elevated proportions of female-producing sperm

Sperm sex ratio adjustment in a mammal: perceived male competition leads to elevated proportions of female-producing sperm. Renée C. Firman, Jamie N. Tedeschi and Francisco Garcia-Gonzalez. Biology Letters, June 3 2020. https://doi.org/10.1098/rsbl.2019.0929

Abstract: Mammal sex allocation research has focused almost exclusively on maternal traits, but it is now apparent that fathers can also influence offspring sex ratios. Parents that produce female offspring under conditions of intense male–male competition can benefit with greater assurance of maximized grand-parentage. Adaptive adjustment in the sperm sex ratio, for example with an increase in the production of X-chromosome bearing sperm (CBS), is one potential paternal mechanism for achieving female-biased sex ratios. Here, we tested this mechanistic hypothesis by varying the risk of male–male competition that male house mice perceived during development, and quantifying sperm sex ratios at sexual maturity. Our analyses revealed that males exposed to a competitive ‘risk’ produced lower proportions of Y-CBS compared to males that matured under ‘no risk’ of competition. We also explored whether testosterone production was linked to sperm sex ratio variation, but found no evidence to support this. We discuss our findings in relation to the adaptive value of sperm sex ratio adjustments and the role of steroid hormones in socially induced sex allocation.

4. Discussion

Recent research has indicated that the sperm sex ratio is a plastic trait that responds to prevailing social conditions [9], which highlights the potential that these adjustments function as a mechanism of male-driven sex allocation [31–34]. In a previous experiment on house mice, we found that exposure to high-male density conditions during sexual development (3–12 weeks of age) resulted in the production of higher proportions of Y-CBS and larger testes [9], which taken together support the male fertility hypothesis [31]. Despite there being strong evidence that low testosterone levels lead to the production of female offspring [45], the precise mechanism by which testosterone influences sperm sex ratios is currently unknown. In the current investigation, we tested whether sperm sex ratio adjustments are linked to variation in testosterone production. Contrary to our expectation, we found that males reared under a risk of competition produced lower sperm sex ratios (i.e. more X-CBS biased) compared with males that matured in the absence of rivals. It is interesting that males exposed to the competitive environment in the current experiment (risk) produced more X-CBS biased sperm ratios than males exposed to the non-competitive environment (no risk), while the opposite result was observed in our previous study (competitive environment = ‘high-male density’; non-competitive = ‘high-female density’) [9]. While these results are seemingly contradictory, differences in experimental design are likely to account for the different responses. The degree of perceived male–male competition was comparatively less intense in our previous experiment (i.e. males maturing within the same room as other males; [9]) than what was applied in the current experiment (i.e. rival males maturing within close proximity to one another within the same experimental tub), which highlights the intriguing possibility that variation in the intensity of competition (and not just presence/absence) leads to different sperm sex ratio responses.

Theory predicts that it would be maladaptive for parents to produce male offspring in a mate competitive environment because they would be forced to compete for access to females and/or be subjected to sperm competition [20]. Conversely, with guaranteed mate availability, high-male density conditions will be evolutionarily favourable for females. Thus, the production of daughters under these conditions is expected to be advantageous to both mothers and fathers [20]. Adaptive maternal sex allocation in relation to male density within the local neighbourhood has been demonstrated in diverse species, including spider mites [21] and house mice [29]. Here, we used house mice sourced from an island population where dispersal capacity is severely restricted and consequently parents and offspring often experience the same local social conditions (see the electronic supplementary material for more information). As a consequence, it is likely that males are forced to compete with both related (sensu local mate competition; [20]) and unrelated males for access to females. We demonstrated that male house mice reared under conditions of intense male–male competition produced higher proportions of X-CBS relative to males not subjected to competition—an outcome that has the potential to have adaptive paternal consequences. Certainly, if increased numbers of female-producing sperm translate to more female offspring, sperm sex ratio adjustments could potentially be an effective strategy for males to enhance their grand-parentage under competitive conditions. We plan to explore this currently untested hypothesis in our future research.

The precise mechanism(s) controlling sex allocation in mammals is currently not well understood. In terms of paternally driven proximate mechanisms, recent research has linked variation in sperm sex ratios [34] and differential X- and Y-CBS motility to offspring sex ratios [46,47]. Further to this, there is evidence to suggest that the ultimate cause of socially induced sex ratio biases involves physiological responses via endocrine signalling [30,48]. Here, we found that the social environment influenced testosterone concentration, but only as a consequence of elevated levels in a subset of ‘risk’ males. Although these individuals produced proportions of Y-CBS at the lower end of the scale, our statistical analyses provided no evidence that sperm sex ratio plasticity is driven by variation in testosterone production. The division in testosterone levels in the ‘risk’ treatment (i.e. less than 20 ng ml⁻¹ and greater than 30 ng ml⁻¹) may be indicative of hormone profiles linked to social status. The default assumption is that social hierarchies are associated with differential testosterone levels, but, in fact, more often than not there is no predictive pattern (e.g. see [49] and references therein). For example, it is only the most aggressive dominant male mice that display elevated testosterone levels (relative to less aggressive dominant males and subordinate males) [49], which likely explains the pattern we have observed in our ‘risk’ treatment. Stress hormones, such as corticosterone, are more commonly associated with social status in male mice, although the direction of the effect has been inconsistent [49]. Offspring sex ratio biases have been linked to maternal stress in a number of mammals [29,30], yet the role that paternal stress plays in sex allocation remains an open question. To address this gap in knowledge, our future research will focus on the relationship between socially induced paternal stress and variation in the sperm sex ratio.

The Earliest Origins of Genetic Nurture: The Prenatal Environment Mediates the Association Between Maternal Genetics and Child Development

The Earliest Origins of Genetic Nurture: The Prenatal Environment Mediates the Association Between Maternal Genetics and Child Development. Emma Armstrong-Carter et al. Psychological Science, June 2, 2020. https://doi.org/10.1177/0956797620917209

Abstract: Observed genetic associations with educational attainment may be due to direct or indirect genetic influences. Recent work highlights genetic nurture, the potential effect of parents’ genetics on their child’s educational outcomes via rearing environments. To date, few mediating childhood environments have been tested. We used a large sample of genotyped mother–child dyads (N = 2,077) to investigate whether genetic nurture occurs via the prenatal environment. We found that mothers with more education-related genes are generally healthier and more financially stable during pregnancy. Further, measured prenatal conditions explain up to one third of the associations between maternal genetics and children’s academic and developmental outcomes at the ages of 4 to 7 years. By providing the first evidence of prenatal genetic nurture and showing that genetic nurture is detectable in early childhood, this study broadens our understanding of how parental genetics may influence children and illustrates the challenges of within-person interpretation of existing genetic associations.

Keywords: genetics, childhood development, prenatal