scholarly journals Limits to Genomic Divergence Under Sexually Antagonistic Selection

2019 ◽  
Author(s):  
Katja R. Kasimatis ◽  
Peter L. Ralph ◽  
Patrick C. Phillips
Keyword(s):  
Genetic Model ◽  
Empirical Studies ◽  
Genetic Load ◽  
Small Sample ◽  
Sampling Variance ◽  
Antagonistic Selection ◽  
Genome Wide ◽  
Sexually Antagonistic Selection ◽  
Small Sample Sizes ◽  
The Relationship

AbstractSince the autosomal genome is shared between the sexes, sex-specific fitness optima present an evolutionary challenge. While sexually antagonistic selection might favor different alleles within females and males, segregation randomly reassorts alleles at autosomal loci between sexes each generation. This process of homogenization during transmission thus prevents between-sex allelic divergence generated by sexually antagonistic selection from accumulating across multiple generations. However, recent empirical studies have reported high male-female FST statistics. Here, we use a population genetic model to evaluate whether these observations could plausibly be produced by sexually antagonistic selection. To do this, we use both a single-locus model with nonrandom mate choice, and individual-based simulations to study the relationship between strength of selection, degree of between-sex divergence, and the associated genetic load. We show that selection must be exceptionally strong to create measurable divergence between the sexes and that the decrease in population fitness due to this process is correspondingly high. Individual-based simulations with selection genome-wide recapitulate these patterns and indicate that small sample sizes and sampling variance can easily generate substantial male-female divergence. We therefore conclude that caution should be taken when interpreting autosomal allelic differentiation between the sexes.

scholarly journals Defining the biological bases of individual differences in musicality

2015 ◽  
Vol 370 (1664) ◽  
pp. 20140092 ◽  
Author(s):  
Bruno Gingras ◽  
Henkjan Honing ◽  
Isabelle Peretz ◽  
Laurel J. Trainor ◽  
Simon E. Fisher
Keyword(s):  
Large Scale ◽  
Twin Studies ◽  
Small Sample ◽  
Aptitude Tests ◽  
Large Scale Assessment ◽  
Genome Wide ◽  
Entry Points ◽  
High Heritability ◽  
Small Sample Sizes ◽  
Complex Human Traits

Advances in molecular technologies make it possible to pinpoint genomic factors associated with complex human traits. For cognition and behaviour, identification of underlying genes provides new entry points for deciphering the key neurobiological pathways. In the past decade, the search for genetic correlates of musicality has gained traction. Reports have documented familial clustering for different extremes of ability, including amusia and absolute pitch (AP), with twin studies demonstrating high heritability for some music-related skills, such as pitch perception. Certain chromosomal regions have been linked to AP and musical aptitude, while individual candidate genes have been investigated in relation to aptitude and creativity. Most recently, researchers in this field started performing genome-wide association scans. Thus far, studies have been hampered by relatively small sample sizes and limitations in defining components of musicality, including an emphasis on skills that can only be assessed in trained musicians. With opportunities to administer standardized aptitude tests online, systematic large-scale assessment of musical abilities is now feasible, an important step towards high-powered genome-wide screens. Here, we offer a synthesis of existing literatures and outline concrete suggestions for the development of comprehensive operational tools for the analysis of musical phenotypes.

scholarly journals The relationship between dose and serotonin transporter occupancy of antidepressants—a systematic review

2021 ◽  
Author(s):  
Anders Sørensen ◽  
Henricus G. Ruhé ◽  
Klaus Munkholm
Keyword(s):  
Serotonin Transporter ◽  
Antidepressant Treatment ◽  
Imaging Techniques ◽  
Small Sample ◽  
Short Treatment ◽  
Predicted Values ◽  
Small Sample Sizes ◽  
The Relationship ◽  
Short Treatment Duration

AbstractBrain imaging techniques enable the visualization of serotonin transporter (SERT) occupancy as a measure of the proportion of SERT blocked by an antidepressant at a given dose. We aimed to systematically review the evidence on the relationship between antidepressant dose and SERT occupancy. We searched PubMed and Embase (last search 20 May 2021) for human in vivo, within-subject PET, or SPECT studies measuring SERT occupancy at any dose of any antidepressant with highly selective radioligands ([11C]-DASB, [123I]-ADAM, and [11C]-MADAM). We summarized and visualized the dose-occupancy relationship for antidepressants across studies, overlaying the plots with a curve based on predicted values of a standard 2-parameter Michaelis–Menten model fitted using the observed data. We included seventeen studies of 10 different SSRIs, SNRIs, and serotonin modulators comprising a total of 294 participants, involving 309 unique occupancy measures. Overall, following the Michaelis–Menten equation, SERT occupancy increased with a higher dose in a hyperbolic relationship, with occupancy increasing rapidly at lower doses and reaching a plateau at approximately 80% at the usual minimum recommended dose. All the studies were small, only a few investigated the same antidepressant, dose, and brain region, and few reported information on factors that may influence SERT occupancy. The hyperbolic dose-occupancy relationship may provide mechanistic insight of relevance to the limited clinical benefit of dose-escalation in antidepressant treatment and the potential emergence of withdrawal symptoms. The evidence is limited by non-transparent reporting, lack of standardized methods, small sample sizes, and short treatment duration. Future studies should standardize the imaging and reporting procedures, measure occupancy at lower antidepressant doses, and investigate the moderators of the dose-occupancy relationship.

scholarly journals Resting heart rate and psychopathy: Findings from the Add Health Survey

2017 ◽  
Author(s):  
Nicholas Kavish ◽  
Q. John Fu ◽  
Michael G. Vaughn ◽  
Zhengmin Qian ◽  
Brian B. Boutwell
Keyword(s):  
Heart Rate ◽  
Small Body ◽  
Psychopathic Traits ◽  
Small Sample ◽  
Future Research ◽  
Alternative Measure ◽  
Resting Heart Rate ◽  
Nationally Representative ◽  
Small Sample Sizes ◽  
The Relationship

AbstractDespite the prior linkages of low resting heart rate to antisocial behavior broadly defined, less work has been done examining possible associations between heart rate to psychopathic traits. The small body of research on the topic that has been conducted so far seems to suggest an inverse relationship between the two constructs. A smaller number of studies have found the opposite result, however, and some of the previous studies have been limited by small sample sizes and unrepresentative samples. The current study attempts to help clarify the relationship between resting heart rate and psychopathic traits in a large, nationally representative sample (analytical N ranged from 14,173-14,220) using an alternative measure of psychopathic traits that is less focused on antisocial processes, and rooted in personality traits. No significant relationship between heart rate and psychopathic traits, or heart rate and a measure of cold heartedness, was found after controlling for age, sex, and race. Implications of the findings, study limitations, and directions for future research are discussed.

The Relationship Between Sample Sizes and Effect Sizes in Systematic Reviews in Education

2009 ◽  
Vol 31 (4) ◽  
pp. 500-506 ◽  
Author(s):  
Robert Slavin ◽  
Dewi Smith
Keyword(s):  
Sample Size ◽  
Effect Size ◽  
Secondary Mathematics ◽  
Significant Negative Correlation ◽  
Small Sample ◽  
Effect Sizes ◽  
Sample Sizes ◽  
Large Samples ◽  
Small Sample Sizes ◽  
The Relationship

Research in fields other than education has found that studies with small sample sizes tend to have larger effect sizes than those with large samples. This article examines the relationship between sample size and effect size in education. It analyzes data from 185 studies of elementary and secondary mathematics programs that met the standards of the Best Evidence Encyclopedia. As predicted, there was a significant negative correlation between sample size and effect size. The differences in effect sizes between small and large experiments were much greater than those between randomized and matched experiments. Explanations for the effects of sample size on effect size are discussed.

Empirical Studies of Transferability of Helsinki Metropolitan Area Travel Forecasting Models

1997 ◽  
Vol 1607 (1) ◽  
pp. 38-44 ◽  
Author(s):  
Nina Karasmaa ◽  
Matti Pursula
Keyword(s):  
Metropolitan Area ◽  
Model Updating ◽  
Statistical Tests ◽  
Empirical Studies ◽  
Estimation Procedure ◽  
Small Sample ◽  
Distribution Models ◽  
Travel Forecasting ◽  
The Difference ◽  
Small Sample Sizes

The temporal transferability of mode choice and trip distribution models was studied by using the data based on traffic surveys in the Helsinki, Finland, metropolitan area in 1981 and 1988. The updating procedures examined were the Bayesian updating, combined transfer estimation, transfer scaling, and joint context estimation procedures. The results of model updating indicated that finding the correct method and sample size for each case is not an unambiguous task. The best method depends on the difference in model coefficients between the initial and the final stages as well as the quality of the data. According to the statistical tests, no differences could be discerned between the models at all. However, the sample enumeration test proved that the models’ ability to predict changes in behavior can vary greatly according to the method used. On the basis of this research the transfer scaling seems to be the method best suited for simple models. In particular, the method is quite useful if the transfer bias is large. The combined transfer estimation procedure performs best when there is a great number of observations and the transfer bias is small. With small sample sizes the Bayesian approach and the joint context estimation give the best results.

scholarly journals Genomic signatures of inbreeding and genetic load in a threatened rattlesnake

2021 ◽  
Author(s):  
Alexander Ochoa ◽  
H. Lisle Gibbs
Keyword(s):  
Threatened Species ◽  
Empirical Studies ◽  
Genetic Load ◽  
Population History ◽  
Deleterious Mutations ◽  
Genetic Rescue ◽  
Isolated Populations ◽  
Genome Wide ◽  
The Impact

Theory predicts that threatened species living in small populations will experience high levels of inbreeding that will increase their negative genetic load but recent work suggests that the impact of load may be minimized by purging resulting from long term population bottlenecks. Empirical studies that examine this idea using genome-wide estimates of inbreeding and genetic load in threatened species are limited. Here we use genome resequencing data to compare levels of inbreeding, levels of genetic load and population history in threatened Eastern massasauga rattlesnakes (Sistrurus catenatus) which exist in small isolated populations and closely-related yet outbred Western massasauga rattlesnakes (S. tergeminus). In terms of inbreeding, S. catenatus genomes had a greater number of ROHs of varying sizes indicating sustained inbreeding through repeated bottlenecks when compared to S. tergeminus. At the species level, outbred S. tergeminus had higher genome-wide levels of genetic load in the form of greater numbers of derived deleterious mutations compared to S. catenatus presumably due to long-term purging of deleterious mutations in S. catenatus. In contrast, mutations that escaped the “drift sieve” and were polymorphic within S. catenatus populations were more abundant and more often found in homozygote genotypes than in S. tergeminus suggesting a reduced efficiency of purifying selection in smaller S. catenatus populations. Our results support an emerging idea that the historical demography of a threatened species has a significant impact on the type of genetic load present which impacts implementation of conservation actions such as genetic rescue.

scholarly journals What’s in a Coefficient? The “Not so Simple” Interpretation of R2, for Relatively Small Sample Sizes

2019 ◽  
Vol 7 (12) ◽  
pp. 27
Author(s):  
Nizar Zaarour ◽  
Emanuel Melachrinoudis
Keyword(s):  
Standard Deviation ◽  
Linear Regression ◽  
Small Sample ◽  
Coefficient Of Determination ◽  
Simple Linear Regression ◽  
Sample Sizes ◽  
Simple Interpretation ◽  
Small Sample Sizes ◽  
Level Of Significance ◽  
The Relationship

There are several misconceptions when interpreting the values of the coefficient of determination, R2, in simple linear regression. R2 is heavily dependent on sample size n and the type of data being analyzed but becomes insignificant when working with very large sample sizes. In this paper, we comment on these observations and develop a relationship between R2, n, and the level of significance α, for relatively small sample sizes. In addition, this paper provides a simplified version of the relationship between R2 and n, by comparing the standard deviation of the dependent variable, Sy, to the standard error of the estimate, Se. This relationship will serve as a safe lower bound to the values of R2. Computational experiments are performed to confirm the results from both models. Even though the focus of the paper is on simple linear regression, we present the groundwork for expanding our two models to the multiple regression case.

scholarly journals Resting Heart Rate and Psychopathy Revisited: Findings From the Add Health Survey

2018 ◽  
Vol 63 (4) ◽  
pp. 543-557 ◽  
Author(s):  
Nicholas Kavish ◽  
Q. John Fu ◽  
Michael G. Vaughn ◽  
Zhengmin Qian ◽  
Brian B. Boutwell
Keyword(s):  
Heart Rate ◽  
Antisocial Behavior ◽  
Small Body ◽  
Psychopathic Traits ◽  
Small Sample ◽  
Alternative Measure ◽  
Resting Heart Rate ◽  
Nationally Representative ◽  
Small Sample Sizes ◽  
The Relationship

Despite the prior linkages of low resting heart rate to antisocial behavior broadly defined, less work has been done examining possible associations between heart rate to psychopathic traits. The small body of research on the topic that has been conducted so far seems to suggest an inverse relationship between the two constructs. A smaller number of studies has found the opposite result, however, and some of the previous studies have been limited by small sample sizes and unrepresentative samples. The current study attempts to help clarify the relationship between resting heart rate and psychopathic traits in a large, nationally representative sample (analytical N ranged from 14,173-14,220) using an alternative measure of psychopathic traits that is less focused on antisocial processes, and rooted in personality traits. No significant relationship between heart rate and psychopathic traits, or heart rate and a measure of cold-heartedness, was found. It is possible that previous findings of a link between heart rate and psychopathy have been driven by the inclusion of overt antisocial behavior in many traditional psychopathy measures. Further work is needed to confirm the associations (or lack thereof) between heart rate and the behavioral, affective, and personality trait aspects of psychopathy.

Cluster headache is associated with an increased risk of depression: A nationwide population-based cohort study

Cephalalgia ◽  
2012 ◽  
Vol 33 (3) ◽  
pp. 182-189 ◽  
Author(s):  
Jen-Feng Liang ◽  
Yung-Tai Chen ◽  
Jong-Ling Fuh ◽  
Szu-Yuan Li ◽  
Chia-Jen Liu ◽  
...  
Keyword(s):  
Risk Factor ◽  
Cluster Headache ◽  
Population Based ◽  
Small Sample ◽  
Cross Sectional ◽  
Increased Risk ◽  
Taiwan National Health Insurance ◽  
Small Sample Sizes ◽  
The Relationship

Objective To investigate whether cluster headache (CH) was a risk factor for depression in a nationwide population-based follow-up study. Background There are few studies about the relationship between CH and depression, and prior research has been limited by cross-sectional studies or small sample sizes. Methods We identified 673 CH patients from the Taiwan National Health Insurance database between 2005 and 2009. The two comparison cohorts included age-, sex- and Charlson’s score-matched migraine patients ( n = 2692) and controls (patients free from migraine or CH, n = 2692). The cumulative incidence of depression was compared among these three cohorts until the end of 2009. We also calculated predictors of depression in the CH cohort. Results After the median 2.5-year follow-up duration, the CH cohort had a greater risk for developing depression compared to the control cohort (adjusted hazard ratio; aHR = 5.6, 95% CI 3.0–10.6, p < 0.001) but not the migraine cohort (aHR = 1.1, 95% CI 0.7–1.7, p = 0.77). Of the CH patients, the number of cluster bout periods per year was a risk factor for depression (aHR = 3.8, 95% CI 2.6–5.4, p < 0.001). Conclusion Our results showed that CH is associated with an increased risk for depression. The strength of this association is similar to that of migraine.

Examining the Relationship Between Weapon Type and Relationship Type in American Homicides: A Bayesian Approach

2020 ◽  
Author(s):  
Joshua J Reynolds ◽  
Paul - Christian Bürkner
Keyword(s):  
Bayesian Approach ◽  
Past Research ◽  
Small Sample ◽  
Limited Data ◽  
Relationship Type ◽  
Final Model ◽  
Categorical Regression ◽  
Small Sample Sizes ◽  
The Relationship ◽  
Data Analytic

Past research indicates that weapon type used in a homicide predicts the victim-perpetrator relationship. Limitations include small sample sizes, inconsistent findings, and limited data analytic techniques. To address these limitations, we examined 363,927 homicides and used Bayesian multilevel categorical regression. In addition to analyzing weapon type (final model consisted of 16 weapon categories), we examined the victims’ sex, age, and race as covariates and modeled the data across states and counties. Results indicate that weapon type is highly informative, however, the age of the victim and sex of the victim interact with weapon type in important ways.

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