Showing papers in "Behavior Genetics in 1998"
TL;DR: Replicated within-family selection for increased voluntary wheel running in outbred house mice (Mus domesticus) was applied with four high-selected and four control lines (10 families/line) and resulted in an average 75% increase in activity in the four selected lines, as compared with control lines.
Abstract: Replicated within-family selection for increased voluntary wheel running in outbred house mice (Mus domesticus; Hsd:ICR strain) was applied with four high-selected and four control lines (10 families/line). Mice were housed individually with access to activity wheels for a period of 6 days, and selection was based on the mean number of revolutions run on days 5 and 6. Prior to selection, heritabilities of mean revolutions run per day (rev/day), average running velocity (rpm), and number of minutes during which any activity occurred (min/day) were estimated by midparent-offspring regression. Heritabilities were 0.18, 0.28, and 0.14, respectively; the estimate for min/day did not differ significantly from zero. Ten generations of selection for increased rev/day resulted in an average 75% increase in activity in the four selected lines, as compared with control lines. Realized heritability averaged 0.19 (range, 0.12-0.24 for the high-activity lines), or 0.28 when adjusted for within-family selection. Rev/day increased mainly through changes in rpm rather than min/day. These lines will be studied for correlated responses in exercise physiology capacities and will be made available to other researchers on request.
373 citations
TL;DR: A testable behavior-genetic model for the development of antisocial behavior is outlined, in which genes and environments promoting or discouraging antissocial behavior become concentrated within families (due to assortative mating), giving rise to widely varying individual developmental trajectories that are, nevertheless, similar within families.
Abstract: Do people mate assortatively for antisocial behavior? If so, what are the implications for the development and persistence of antisocial behavior? We investigated assortative mating for antisocial behavior and its correlates in a sample of 360 couples from Dunedin, New Zealand. We found substantial assortative mating for self-reports of antisocial behavior per se and for self-reports of couple members' tendencies to associate with antisocial peers (0.54 on average). Perceptions about the likelihood of social sanctions for antisocial behavior (e.g., being caught by the authorities or losing the respect of one's family) showed moderate assortative mating (0.32 on average). However, assortative mating for personality traits related to antisocial behavior was low (0.15 on average). These findings suggest that, whereas assortative mating for many individual-difference variables (such as personality traits) is low, assortative mating for actual antisocial behaviors is substantial. We conclude that future family studies of antisocial behavior should endeavor to measure and understand the influence of assortative mating. In addition, we outline a testable behavior-genetic model for the development of antisocial behavior, in which genes and environments promoting or discouraging antisocial behavior become concentrated within families (due to assortative mating), giving rise to widely varying individual developmental trajectories that are, nevertheless, similar within families.
289 citations
TL;DR: This study shows that the zygosity of same-sexed twins more than 2 years old and without gross physical malformation can reliably be determined by a telephone questionnaire with a high accuracy.
Abstract: The aim of this study was to validate a zygosity questionnaire that can be administered over the telephone Mothers of same-sexed twins of known zygosity and chorionicity between 2 and 31 years of age were interviewed on a nine-item questionnaire From the answers one unweighted and four weighted indices were computed As single questions, the mother's opinion and the “two peas in a pod” question differentiated best between monozygotic and dizygotic twins One independent well-trained observer assessed the zygosity based on the questionnaire and made the correct diagnosis in 96% of the cases A weighted index of eight similarity questions yielded an accuracy of 98% This study shows that the zygosity of same-sexed twins more than 2 years old and without gross physical malformation can reliably be determined by a telephone questionnaire with a high accuracy
175 citations
TL;DR: Examining quantitatively the effect of within-strain sample size (n) on additive QTL mapping efficiency and comparisons with F2and backcross (BC) populations suggested that RI populations are more cost-effective than conventional selectively genotyped F2populations at values likely to be seen in behavioral studies.
Abstract: Increasing the number of mice used to calculate recombinant inbred (RI) strain means increases the accuracy of determining the phenotype associated with each genotype (strain), which in turn enhances quantitative trait locus (QTL) detection and mapping. The purpose of this paper is to examine quantitatively the effect of within-strain sample size (n) on additive QTL mapping efficiency and to make comparisons with F2and backcross (BC) populations, where each genotype is represented by only a single mouse. When 25 RI strains are used, the estimated equivalent number of F2mice yielding the same power to detect QTLs varies inversely as a function of the heritability of the trait in the RI population \(h_{{\text{RI}}}^{\text{2}} \). For example, testing 25 strains with n= 10 per strain is approximately equivalent to 160 F2mice when \(h_{{\text{RI}}}^{\text{2}} \)= 0.2, but only 55 when \(h_{{\text{RI}}}^{\text{2}} \)= 0.6. While increasing nis always beneficial, the gain in power as nincreases is greatest when \(h_{{\text{RI}}}^{\text{2}} \)is low and is much diminished at high \(h_{{\text{RI}}}^{\text{2}} \)values. Thus, when \(h_{{\text{RI}}}^{\text{2}} \)is high, there is little advantage of large n, even when napproaches infinity. A cost analysis suggested that RI populations are more cost-effective than conventional selectively genotyped F2populations at \(h_{{\text{RI}}}^{\text{2}} \)values likely to be seen in behavioral studies. However, with DNA pooling, this advantage is greatly reduced and may be reversed depending on the values of \(h_{{\text{RI}}}^{\text{2}} \)and n.
164 citations
TL;DR: The heritability of total plasma testosterone levels, determined from blood samples, was examined in 160 adolescent twin pairs and their parents and the lack of father–son resemblance suggests that different genetic factors may be expressed in adolescence and adulthood.
Abstract: The heritability of total plasma testosterone levels, determined from blood samples, was examined in 160 adolescent twin pairs and their parents. Subjects were tested as part of a larger study of cardiovascular risk factors, conducted in Amsterdam. Each subject provided a sample of blood which was assayed to measure testosterone concentrations. Correlations of testosterone in monozygotic twins were higher than in dizygotic twins. No resemblance was found between testosterone values in fathers and those in their children and a moderate correlation was seen between mothers and their daughters. The lack of resemblance between family members of opposite sex suggests that different genetic factors influence plasma testosterone concentrations in men and women. In adolescent men, approximately 60% of the variance in testosterone levels is heritable. The lack of father-son resemblance suggests that different genetic factors may be expressed in adolescence and adulthood. In women, 40% of the variance in testosterone levels is heritable, both in adolescence and in adulthood.
163 citations
TL;DR: The relation of the dopamine transporter gene (DAT1) to symptoms of internalizing disorders, Tourette's disorder, and obsessive-compulsive disorder was examined using both within- and between-family tests of association.
Abstract: The relation of the dopamine transporter gene (DAT1) to symptoms of internalizing disorders, Tourette's disorder, and obsessive-compulsive disorder was examined using both within- and between-family tests of association. The sample consisted of clinic-referred children and their siblings and controls and their siblings. Between-family association was examined via the association of DAT1 genotypes with disorder symptoms in the population. Symptoms of all eight disorders increased with a greater number of 10-repeat DAT1 alleles. Using a quantitative transmission disequilibrium test (QTDT), linkage and within-family association was indicated by increased symptoms in children who received 10 repeat alleles from heterozygous parents relative to children who received 9 repeat alleles. Four disorders were associated with DAT1 using the QTDT: generalized anxiety, social phobia, obsessive-compulsive, and Tourette's. The effects of comorbidity were investigated by repeating the same between- and within-family analyses on residual scores, with any effects of attention deficit hyperactivity disorder symptoms removed. Although the residuals were associated less strongly with DAT1 than were the original scores, three disorders continued to show association both between and within families: generalized anxiety, Tourette's, and social phobia.
134 citations
TL;DR: Power to detect genetic and environmental influences increases not only with sample size but also with the number of measurements through longitudinal and/or multivariate designs, if those measurements correlate with each other.
Abstract: Power to detect genetic and environmental influences increases not only with sample size but also with the number of measurements through longitudinal and/or multivariate designs, if those measurements correlate with each other. Power simulations are presented for uni- through quadrivariate cases, with differing genetic and environmental parameters. Even though subject attrition is a problem for most longitudinal studies, the gain in power available may more than make up for this shortcoming in many situations. In terms of planning studies to examine genetic and environmental influences, power calculations should not only consider sample size but number of measurements on particular phenotypes and their intercorrelations.
130 citations
TL;DR: Model-fitting results suggested that ADHD symptomatology is highly heritable and influenced mostly by additive genetic, specific environmental, and contrast effects, but this analysis could not exclude with statistical significance additional effects from dominance.
Abstract: The magnitude of genetic and environmental factors and the influence of contrast effects on attention-deficit hyperactivity disorder (ADHD) symptomatology were examined on a sample of 900 twin pairs, aged 7–13, participating in the Virginia Twin Study of Adolescent Behavioral Development (VTSABD). In addition, the genetic and environmental correlations between ADHD and oppositional-defiant disorder/conduct disorder (ODD/CD) symptomatology were estimated. A series of structural models was applied to maternal ratings from a telephone survey, designed to screen for the three dimensions of ADHD symptomatology (hyperactivity, impulsivity, and inattention) and ODD/CD symptomatology. Model-fitting results suggested that ADHD symptomatology is highly heritable and influenced mostly by additive genetic, specific environmental, and contrast effects. However, this analysis could not exclude with statistical significance additional effects from dominance. The results of the best-fitting bivariate model suggested that the genetic correlation between the two traits is 50% and replicated previous findings of a common genetic factor influencing the comorbidity of ADHD and ODD/CD symptomatologies.
116 citations
TL;DR: Results indicate that genetic factors contribute substantially to individual differences in adolescent BMI, explaining between 45 and 85% of the variance in BMI, and based on an analysis of opposite-sex sibling pairs, the genes that influence variation in adolescents BMI are similar for males and females.
Abstract: The present study uses a behavioral genetic design to investigate the genetic and environmental influences on variation in adolescent body mass index (BMI) and to determine whether the relative influences of genetic and environmental factors on variation in BMI are similar across racial groups and sexes. Data for the present study come from the National Longitudinal Study on Adolescent Health (Add Health), a large, nationally representative study of adolescent health and health-related behaviors. The Add Health sample contains a subset of sibling pairs that differs in levels of genetic relatedness, making it well suited for behavioral genetics analyses. The present study examines whether genetic and environmental influences on adolescent BMI are the same for males and females and for Black and White adolescents. Results indicate that genetic factors contribute substantially to individual differences in adolescent BMI, explaining between 45 and 85% of the variance in BMI. Furthermore, based on an analysis of opposite-sex sibling pairs, the genes that influence variation in adolescent BMI are similar for males and females. However, the relative importance of genetic and environmental influences on variation in BMI differs for males and females and for Blacks and Whites. Although parameter estimates could be constrained to be equal for Black and White males, they could not be constrained to be equal for Black and White females. Moreover, the best-fitting model for Black females was an ADE model, for White females it was an ACE model, and for males it was an AE model. Thus, shared environmental influences are significant for White female adolescents, but not for Black females or males. Likewise, nonadditive genetic influences are indicated for Black females, but not for White females or males. Implications of these results are discussed.
110 citations
TL;DR: The results indicate the presence of cues that could allow adult mice to behave differentially toward pups as a function of their age and sex.
Abstract: Infant house mice, Mus musculus, produce ultrasonic calls that reliably lead to retrieval by adult mice While individual differences in calls have been demonstrated both among and within species, the influences of age and sex on call characteristics have not been systematically investigated in mice This study examined the influences of age, sex, and genotype (inbred versus hybrid) on the rate, length, and frequency characteristics of the calls of 486 male and female mice from 2 to 12 days of age Rate of calling followed a shallow inverted U-shaped function across days Call lengths decreased and call frequency characteristics increased, in a linear manner, with age Females emitted fewer calls, with a smaller bandwidth, at some ages than males Hybrid pups produced more calls of greater length and a lower frequency than inbred pups These results indicate the presence of cues that could allow adult mice to behave differentially toward pups as a function of their age and sex
79 citations
TL;DR: The use of factor scores is shown to be universally more powerful than the use of multivariate or mean phenotypic data and the effect of using a single sample of sib-pairs to both calculate the factor score regression matrix and to carry out the QTL analysis is investigated.
Abstract: The power to detect a quantitative trait locus (QTL) in sib-pair data is investigated. We assume that we have at our disposal 3 or 4 related phenotypic measures in a sample of sib-pairs. Individual differences in these phenotypes are due to a common QTL and specific (i.e., unique to each phenotype) nonshared environmental and specific polygenic additive effects. In addition, models are considered that include common nonshared environmental effects and/or common polygenic additive effects. We calculate the power to detect the QTL in a genetic covariance structure analysis of the multivariate data, of the mean phenotypic data, and of factor scores. The use of factor scores is shown to be universally more powerful than the use of multivariate or mean phenotypic data. We also investigate the effect of using a single sample of sib-pairs to both calculate the factor score regression matrix and to carry out the QTL analysis. The use of a single sample to both these ends results in a loss of power compared to the theoretical, expected power. The gain in power attributable to the use of factor scores, however, outweighs this observed loss in power. The advantages of using factor scores in selecting sib-pairs are discussed.
TL;DR: The results suggest that individual differences in coherence form a potential candidate for (molecular) genetic studies on brain function as well as environmental factors shared by twin siblings did not influence variation in EEG coherence.
Abstract: EEG coherence measures the covariation in electrical brain activity between two locations on the scalp and is used to study connectivity between cortical regions. The aim of this study was to determine the heritability of EEG coherence. Coherence was measured in a group of 213 16-yr-old twin pairs. By including male and female twin pairs in the sample, sex differences in genetic architecture were systematically examined. The EEG was obtained during quiet supine resting. Coherence was estimated for short and long distance combinations of electrode pairs along the anterior-posterior axis within a hemisphere for four frequency bands (delta, theta, alpha and beta). Averaged over all electrode combinations about 60% of the variance was explained by genetic factors for coherence in the theta, alpha and beta bands. For the delta band, the heritability was somewhat lower. No systematic sex differences in genetic architecture were found. All environmental influences were nonshared, i.e., unique factors including measurement error. Environmental factors shared by twin siblings did not influence variation in EEG coherence. These results suggest that individual differences in coherence form a potential candidate for (molecular) genetic studies on brain function.
TL;DR: This study proposes an iteratively reweighted least squares method (IRWLS), a second-order approximation to ML that is developed in the context of a single large outbred family and compared with REG and ML via replicated Monte Carlo simulations.
Abstract: Mapping quantitative trait loci (QTL) is a typical problem of regression with uncertain independent variables because the genotype of a putative QTL is not observed. Rather, the genotype is inferred from marker information. The method of maximum likelihood (ML) methods is considered to be the optimal solution for this problem because the distribution of the unobserved QTL genotype is fully taken into account. The simple linear regression method (REG) is a first-order approximation to ML and usually performs very well. In this study, an iteratively reweighted least squares method (IRWLS) is proposed. The new method is a second-order approximation to ML because both the expectation and the variance of the unobserved QTL genotype are taken into consideration. The IRWLS is developed in the context of a single large outbred family. The properties of IRWLS are demonstrated and compared with REG and ML via replicated Monte Carlo simulations. The conclusions are: (1) when marker information content is high, the three methods perform equally well, but ML and IRWLS outperform REG when marker information content is low and the variance explained by the QTL is high; (2) when the residual distribution is not normal, ML can fail or have low power to detect small QTLs, but REG and IRWLS are robust to non-normality; and (3) when the residual distribution is normal, the performance of IRWLS is almost identical to ML, but the computational speed of IRWLS is many times faster than that of ML.
TL;DR: It is found that EC-SOD overexpressing mice were resistant to the cognitive effects of L-NAME (NG-nitro-L-arginine methyl ester hydrochloride), an NO synthase inhibitor, and decreased NO catabolism in these mice may have served to counter the effects of NOS inhibition by L- NAME.
Abstract: Extracellular superoxide dismutase (EC-SOD) controls the availability of extracellular superoxide (O2.-), which is important for a variety of physiological pathways, including the primary means of inactivating nitric oxide (NO). The role of EC-SOD in neurobehavioral function has been until now unexplored. In the current studies, the phenotypic expression of genotypic alterations of EC-SOD production in mice were characterized for spatial learning and memory. Dramatic impairments in spatial learning in the win-shift 8-arm radial maze were seen in both EC-SOD knockout mice and EC-SOD overexpressing mice. The EC-SOD overexpressing mice were further characterized as having significant deficits in a repeated acquisition task in the radial-arm maze, which permitted the dissociation of long and short-term learning. Long-term learning was significantly impared by EC-SOD overexpression, whereas short-term learning was not significantly affected by EC-SOD overexpression. No systems have been shown to be importantly involved in learning and memory. This may be important in the current studies because EC-SOD has primary control over the inactivation of NO. We found that EC-SOD overexpressing mice were resistant to the cognitive effects of L-NAME (NG-nitro-L-arginine methyl ester hydrochloride), an NO synthase inhibitor. Decreased NO catabolism in these mice may have served to counter the effects of NOS inhibition by L-NAME. The current finding that EC-SOD levels that were either higher or lower than controls impaired learning demonstrates that the proper control of brain extracellular O2.- may be more vital than merely reduction of brain extracellular O2.- in maintaining adequate learning function.
TL;DR: Oviposition behavior of the four species in the Drosophila melanogastercomplex was investigated versus natural morinda fruit and the two major aliphatic acids of this fruit and a qualitative reversal from preference to avoidance was observed with increasing concentration.
Abstract: Oviposition behavior of the four species in the Drosophila melanogastercomplex (D. melanogaster, D. simulans, D. mauritiana, D. sechellia) was investigated versus natural morinda fruit (the normal resource of D. sechellia) and the two major aliphatic acids of this fruit (hexanoic acid, C6, and octanoic acid, C8). Two different experimental techniques were compared. When control and experimental food were set on the same egg laying plate, three species (D. sechellia, D. mauritiana, D. melanogaster) exhibited a significant preference for morinda; with aliphatic acids, only D. sechelliamanifested a preference. With separate oviposition sites, a preference was found in D. sechelliafor morinda and acids, and a general avoidance behavior in the three other species. Genetic analysis of the behavioral response toward C6 and C8 was done with the two plates technique on D. sechellia, D. simulans, F1 hybrids and backcrosses. Significant behavioral differences were observed with major effects due to genotype, concentration and their interaction. Hybrid behaviors were intermediate between those of their parents. In several cases, a qualitative reversal from preference to avoidance was observed with increasing concentration. In F1 flies, a dominance reversal was observed with increasing C8 concentration. Different reaction thresholds in different receptors might explain such observations.
TL;DR: The stable variance over the 8-year interval was largely environmentally influenced for menstrual flow, was approximately equally determined by genetic and by nonshared environmental influences in the case of pain, and was due almost entirely to genetic influences for limitation by periods.
Abstract: Genetically informative longitudinal data about menstrual disorders allow us to address the extent to which the same genetic risk mechanisms are operating throughout the reproductive life cycle. We investigate the relative contributions of genes and environment to individual differences in menstrual symptomatology reported at two waves, 8 years apart, of a longitudinal Australian twin study. Twins were questioned in 1980-1982 and 1988-1990 about levels of menstrual pain, flow, and perceived limitation by menses. Longitudinal genetic analysis was based on 728 pairs (466 MZ and 262 DZ) who were regularly menstruating at both survey waves. A bivariate Cholesky model was fitted to the two-wave data separately for flow, pain, and limitation variables. The baseline model comprised common genetic and environmental factors influencing responses at both waves and specific effects influencing only the second-wave response. We also included age as a covariate in the model. Proportions of the longitudinally stable variance in menstrual flow, pain, and limitation attributable to genetic and individual environmental effects were calculated for the best-fitting models. Genetic factors accounted for 39% of the longitudinally stable variation in menstrual flow, 55% for pain, and 77% for limitation. The remaining stable variance was due to individual environmental factors (61, 45, and 23%, respectively). Therefore the stable variance over the 8-year interval was largely environmentally influenced for menstrual flow, was approximately equally determined by genetic and by nonshared environmental influences in the case of pain, and was due almost entirely to genetic influences for limitation by periods. We demonstrate for the first time that the same genetic influences are operative throughout the reproductive life span.
TL;DR: The genetic and environmental influences on problem behaviors at two assessment points, three years apart, and their stability were studied in a sample of international adoptees, initially aged 10 to 15 years.
Abstract: The genetic and environmental influences on problem behaviors at two assessment points, three years apart, and their stability were studied in a sample of international adoptees, initially aged 10 to 15 years. Parents of 111 pairs of adopted biological siblings, 221 pairs of adopted nonbiological siblings and 1484 adopted singletons completed the Child Behavior Checklist (75 pairs, 154 pairs and 1080 singletons respectively at second assessment). At first assessment, genetic factors accounted for more than 50% of the variance in the Externalizing, Aggressive Behavior, Attention Problems and Social Problems scales. Shared environmental influences explained 40% of the variance in the Total Problem scale and less for all other scales. Nonshared environmental influences were most important for the Internalizing scale and its subscales, and for the Thought Problems and Delinquent Behavior scales. At the second assessment, genetic factors explained most of the variance in the Total Problem, Externalizing and Aggressive Behavior scales, while nonshared environmental influences explained most of the variance in all other scales. Shared environmental influences explained 33% of the variance in the Internalizing scale and less for the other scales. The stability of the Externalizing scale over time was caused mostly by genetic factors, while nonshared environmental factors mostly caused the stability of the Internalizing scale.
TL;DR: A twin model is proposed and explored to examine the basis for synchrony that often characterizes different facets of normal development and an approach to the analysis of “soft” events; events for which available reports of dates or ages of occurrence are unreliable or inconsistent.
Abstract: We propose and explore a twin model to examine the basis for synchrony that often characterizes different facets of normal development. In so doing we also present an approach to the analysis of “soft” events; events for which available reports of dates or ages of occurrence are unreliable or inconsistent. Discrepancies among reports are accounted for by a statistical measurement model. This combines current status error reflecting uncertain definition of onset and two mechanisms for the phenomenon of “telescoping,” namely, systematic compression of the time scale and heteroscedastic random measurement error. Statistically, the model can be viewed as a mixed generalized linear model with random effects within both mean and variance functions or, alternatively, as involving multiplicative random effects. We apply the model to multiple maternal reports on menarche and onset of breast development in twin daughters. Fitted to data from the Virginia Twin Study Of Adolescent and Behavioral Development by the use of penalized/predictive quasi-likelihood, the model provided much improved estimates of the true age-at-onset distribution as compared to those from a naive analysis. Results suggested that the observed variance was made up almost entirely of genetic variance and measurement error variance due to telescoping and current status errors and that the timing of breast development and menarche are largely under the control of a common set of genes. Results also indicated that maternal recollections of the onset of breast development were both more poorly defined and subject to greater recall errors than maternal recollections of menarche.
TL;DR: The relatively weak and late occurring effects indicate that mate choice based on age may not be a viable strategy in this population of Drosophila melanogaster.
Abstract: We examined the relationship of genetic quality to age in male Drosophila melanogaster to test two contrasting hypotheses. The traditional hypothesis is that older males have proven their viability and therefore produce offspring of superior genetic quality. This hypothesis is often evoked as an explanation for female preference for older mates. In contrast, we have recently argued that older fathers may produce offspring of inferior genetic quality. Here, we present results from an experiment designed to measure the genetic quality of offspring produced by 2 day old, 2 week old and 5 week old male D. melanogaster. We found a statistically significant small reduction in larval viability and a similar but statistically non-significant reduction in son mating ability among the offspring of the 5 week old males. Daughter fecundity showed no apparent trend for a reduction nor an increase in performance with increasing age of the fathers. There was no evidence of a difference between the 2 day old and the 2 week old males for any of these three fitness components. These results are in somewhat better accordance with our alternative hypothesis, but the relatively weak and late occurring effects indicate that mate choice based on age may not be a viable strategy in this population.
TL;DR: The use of data-weighting is illustrated to assess the likely effects of cooperation bias or attrition both on measures of mean or prevalence, and on twin pair correlations or concordances, using data from the Australian twin panel 1981 survey and alcohol challenge studies.
Abstract: Because twins and adoptees are a rare resource, they are often studied repeatedly over a period of many years. Differential attrition, and in some studies initial cooperation bias, have the potential to lead to serious biases to estimates of genetic and environmental parameters. Since non-response is often influenced by multiple binary or categorical sociodemographic variables, maximum-likelihood methods are not easily adapted to adjust for such effects. In this brief note we illustrate the use of data-weighting to assess the likely effects of cooperation bias or attrition both on measures of mean or prevalence, and on twin pair correlations or concordances, using data from the Australian twin panel 1981 survey and alcohol challenge studies. Participants in the alcohol challenge study were on average younger, more socially nonconforming, heavier drinkers, more likely to be unmarried, and less likely to report their religion as Other Protestant. Reweighting the alcohol challenge sample to have the same distribution on these variables as the Australian twin panel 1981 survey respondents confirmed that individuals who would feel very intoxicated after a challenge dose of alcohol were underrepresented in the study. However, pairwise data-weighting indicated that this cooperation bias was leading to only a slight underestimation of the importance of genetic effects on subjective intoxication.
TL;DR: Estimates of bivariate-heritability indicate that on average about half of the phenotypic correlations among the four specific cognitive ability measures are due to genetic effects, which would be interpreted as greater heritability by the parent–offspring design.
Abstract: A parent–offspring multivariate conditional path model was fitted to specific cognitive abilities data from the Colorado Adoption Project (CAP) when the offspring were 12 years of age. The sample included 175 adoptees, 175 sets of adoptive parents, 175 biological mothers, 34 biological fathers, and 209 nonadopted children and their parents. Consistent with results obtained from multivariate genetic analyses of CAP data obtained at earlier ages, the effects of familial environmental transmission on individual differences in specific cognitive abilities were not significant. Assuming complete isomorphism (i.e., that the genetic and environmental etiologies of individual differences are the same) between the child and the adult measures, the heritability estimates for verbal, spatial, perceptual speed, and visual memory were .26, .35, .38, and .53, respectively. Although the heritability estimate for visual memory is somewhat higher than those for verbal, spatial, and perceptual speed abilities, these estimates are not significantly different. These estimates are higher than those obtained when the adoptees and controls were 4 years old (Rice et al., 1986, 1989); thus, heritabilities of specific cognitive abilities may increase as a function of cognitive development. Alternatively, genetic stability from childhood to adulthood may be greater from 12 years than from 4 years, which would be interpreted as greater heritability by the CAP parent–offspring design. The genetic correlations among the four measures were substantial, ranging from .27 between verbal and spatial abilities to .78 between spatial ability and perceptual speed. However, differences among these correlations are not significant, suggesting that their covariation may be due to general cognitive ability. Finally, estimates of bivariate-heritability indicate that on average about half of the phenotypic correlations among the four specific cognitive ability measures are due to genetic effects.
TL;DR: Data from 167 pairs of 5-year-old twins obtained to study genetic and environmental influences on individual differences in intrahemispheric coherences suggest that for corticocortical connections between adjacent brain areas, a large part of the variance is explained by “true” environmental influences, whereas for longer connections, that is, sensory to frontal areas, the variance are mostly genetic in origin.
Abstract: Electroencephalographic (EEG) coherence has been suggested to be an index of the connectivity of the brain. It represents the coupling between two EEG signals from different brain areas and is mathematically analogous to a cross-correlation in the frequency domain. We obtained data from 167 pairs of 5-year-old twins to study genetic and environmental influences on individual differences in intrahemispheric coherences. Coherence was computed in the theta band (4.0 to 7.5 cycles/s) between prefrontal, frontal, central, parietal, and occipital regions during quiet rest. Univariate genetic analyses of the data showed moderate to strong genetic influences for all coherences. Broad heritabilities ranged from 30 to 71%, with a mean heritability of 49%. With one exception, no sex differences were found. Split-half reliabilities varied with interelectrode distances, ranging from .91 for the shortest distance to .62 for the longest distance. When split-half reliabilities are compared with heritabilities, the data suggest that for corticocortical connections between adjacent brain areas, a large part of the variance is explained by “true” environmental influences, whereas for longer connections, that is, sensory to frontal areas, the variance is mostly genetic in origin.
TL;DR: It is suggested that separate genes underlie the strain differences in acceptance of dilute and concentrated NaCl solutions.
Abstract: We examined voluntary NaCl intakes of five mouse strains: NZB/B1NJ, SM/J, 129/J, C57BL/6ByJ, and CBA/J. Using two-bottle tests with water as one choice, the mice were offered series of progressively increasing or progressively decreasing NaCl concentrations (37.5-600 mM NaCl in 48-h tests), then 300 mM NaCl for 6 days and 75 mM NaCl for 8 days. Low concentrations of NaCl were more avidly accepted by mice given the increasing rather than the decreasing series. However, irrespective of the test order, test duration, or how the results were expressed (i.e., as raw intakes, intakes corrected for body weights, or preferences), the NZB/B1NJ mice always had higher NaCl acceptance than did the CBA/J mice. The SM/J, 129/J, and C57BL/6ByJ strains were intermediate between the NZB/B1NJ and the CBA/J strains, but their distributions varied from concentration to concentration. Low ( or = 300 mM) NaCl concentrations were strongly avoided by all mice, except for the NZB/B1NJ strain. It is suggested that separate genes underlie the strain differences in acceptance of dilute and concentrated NaCl solutions.
TL;DR: Early social experiences play important roles in adult Drosophila paulistorummate selection and socially isolated males from all six semispecies also displayed notable frequencies of homosexual behavior.
Abstract: Early social experiences play important roles in adult Drosophila paulistorummate selection. Differences in courtship between control males and wholly socially isolated males were observed in chambers. Socially isolated males displayed more courtship toward virgin females than did controls. Socially isolated males were more successful in competing for mates. Yet socially isolated males from all six semispecies also displayed notable frequencies of homosexual behavior.
TL;DR: The results suggest that the cerebellum, although not necessary for learning a spatial task, plays a crucial role in its retention, and that the storing structure of spatial information differs in +/+ and +/Lc mice.
Abstract: Lurcher mutant mice (+/Lc) exhibit a massive loss of neurons in the cerebellar cortex and the inferior olivary nucleus, while deep cerebellar nuclei are essentially intact. To discriminate the relative participation of the cerebellar cortex and deep structures in learning and memory, 3 to 6-month-old +/Lc mice were subjected to a spatial learning task derived from the Morris water escape. They were able to learn to escape as well as their strain-matched controls (+/+). Seven days later, their scores showed that they had memorized the spatial environment but not as accurately as +/+ mice. Cerebellectomy before training did not significantly alter the escape learning capabilities of either group, whereas cerebellectomy performed after learning completely abolished retention in +/+, as well as in +/Lc, mice. These results suggest that the cerebellum, although not necessary for learning a spatial task, plays a crucial role in its retention, and that the storing structure of spatial information differs in +/+ and +/Lc mice.
TL;DR: A model is presented for the truncated trivariate normal distribution that arises in behavior genetic adoption designs that focus on sibling similarity to estimate shared environmental effects and results indicate that the point of truncation is at about the 63rd percentile of the family environmental quality distribution.
Abstract: A model is presented for the truncated trivariate normal distribution that arises in behavior genetic adoption designs that focus on sibling similarity to estimate shared environmental effects. The model estimates the point of truncation and shared environmentality. Both moment and maximum likelihood estimates are obtained numerically. Simulations indicate that the model and the numerical procedures perform well when they are most needed, that is, when shared environmentality is large, truncation is extensive or both. When applied to published data from the Texas Adoption Project, results indicate that the point of truncation is at about the 63rd percentile of the family environmental quality distribution (i.e., the bottom 63% is missing) and shared environmentality is about 55%. Implications for current views on the importance of shared environment for child developmental outcomes such as antisocial behavior and IQ are discussed.
TL;DR: The data suggest that the DRD5 locus is involved in the variation and sex dimorphism of substance abuse liability and the genotypes of spouses that could be induced by assortative mating for the liability to substance abuse.
Abstract: We have conducted a population-based association study of substance abuse and a microsatellite at the dopamine D5 receptor locus (DRD5) in a sample of European–American males and females with substance dependence (SA) or without any psychiatric disorder. Overrepresentation of the most frequent allele (148 bp) was found in males in the SA group (OR = 2.2, P= .02); this finding was reproduced in females (OR = 5.4, p< .001). The difference in the frequencies of this allele between SA males and SA females was statistically significant. The genotype coded in accordance with the dose of this allele correlated with substance abuse liability in males and females (stronger in females) and with novelty seeking in females. There was no evidence of correlation between the genotypes of spouses that could be induced by assortative mating for the liability to substance abuse. The data suggest that the DRD5 locus is involved in the variation and sex dimorphism of substance abuse liability.
TL;DR: The aim is to investigate whether optimal selection can be achieved when prior knowledge concerning the QTL gene action, QTL allele frequency,QTL effect size, and background (residual) sib correlation is limited or absent.
Abstract: Percentages of extremely concordant and extremely discordant sib pairs are calculated that maximize the power to detect a quantitative trait locus (QTL) under a variety of circumstances using the EDAC test. We assume a large fixed number of randomly sampled sib pairs, such as one would hope to find in the large twin registries, and limited resources to genotype a certain number of selected sib pairs. Our aim is to investigate whether optimal selection can be achieved when prior knowledge concerning the QTL gene action, QTL allele frequency, QTL effect size, and background (residual) sib correlation is limited or absent. To this end we calculate the best selection percentages for a large number of models, which differ in QTL gene action allele frequency, background correlation, and QTL effect size. By averaging these percentages over gene action, over allele frequency, over gene action, and over allele frequencies, we arrive at general recommendations concerning selection percentages. The soundness of these recommendations is subsequently in a number of test cases.
TL;DR: The validity of a measure of infant–caregiver attachment for twins was assessed and twin similarity for attachment as measured by the Louisville Twin Study procedure was assessed.
Abstract: Two pilot studies were conducted. First, the validity of a measure of infant-caregiver attachment for twins was assessed. Sixteen twin pairs from the Louisville Twin Study (LTS) were assessed in the Strange Situation (SS) at ages 19 or 25 months. Concordance between the LTS procedure and the SS procedure for assessing attachment was 78.1%, significantly greater than chance. Second, twin similarity for attachment as measured by the LTS procedure was assessed. Videotapes of 34 MZ pairs and 26 DZ pairs at ages 18 and 24 months were rated in terms of attachment behavior. MZ concordance for attachment was 67.6%, significantly greater than the DZ concordance rate of 38.5%. Results are discussed in the context of current debate in attachment theory.
TL;DR: There are substantial genetic effects on sleeptalking both in childhood and as adults, which appear to be highly correlated, and in adults psychiatric comorbidity is about twice as common in those with frequent sleeptalk, compared to those with infrequent or no sleeptwalking.
Abstract: Sleeptalking is usually benign but chronic cases in adults may relate to psychopathology. We hypothesize substantial genetic influences in the liability to sleeptalking and an association between sleeptalking and psychiatric disorders. In 1990 a questionnaire sent to the Finnish Twin Cohort yielded responses from 1298 monozygotic and 2419 dizygotic twin pairs aged 33-60 years. We used structural equation modelling to estimate genetic and environmental components of variance in the liability to sleeptalking. Register data on hospitalization and long-term antipsychotic medication were used to assess psychiatric comorbidity. The occurrence of childhood and adult sleeptalking was highly correlated. A gender difference was only seen in adults, with sleeptalking being more common in males than in females. The proportion of total phenotypic variance in liability to sleeptalking attributed to genetic influences in childhood sleeptalking was 54% (95% CI, 44-62%) in males and 51% (43-58%) in females, and for adults it was 37% (27-46%) among males and 48% (40-56%) among females. An association with psychiatric comorbidity was found only in adult sleeptalking, and it was highest in those with adult-onset sleeptalking (odds ratio, 3.77; 95% CI, 2.32-6.17). Sleeptalking is quite a persistent trait, also being common in adults. There are substantial genetic effects on sleeptalking both in childhood and as adults, which appear to be highly correlated. In adults psychiatric comorbidity is about twice as common in those with frequent sleeptalking, compared to those with infrequent or no sleeptalking, but most cases of sleeptalking are not associated with serious psychopathology.