Individual Differences In Activity Level Research Articles

The effects of exploratory behavior on physical activity in a common animal model of human disease, zebrafish (Danio rerio).

Zebrafish (Danio rerio) are widely accepted as a multidisciplinary vertebrate model for neurobehavioral and clinical studies, and more recently have become established as a model for exercise physiology and behavior. Individual differences in activity level (e.g., exploration) have been characterized in zebrafish, however, how different levels of exploration correspond to differences in motivation to engage in swimming behavior has not yet been explored. We screened individual zebrafish in two tests of exploration: the open field and novel tank diving tests. The fish were then exposed to a tank in which they could choose to enter a compartment with a flow of water (as a means of testing voluntary motivation to exercise). After a 2-day habituation period, behavioral observations were conducted. We used correlative analyses to investigate the robustness of the different exploration tests. Due to the complexity of dependent behavioral variables, we used machine learning to determine the personality variables that were best at predicting swimming behavior. Our results show that contrary to our predictions, the correlation between novel tank diving test variables and open field test variables was relatively weak. Novel tank diving variables were more correlated with themselves than open field variables were to each other. Males exhibited stronger relationships between behavioral variables than did females. In terms of swimming behavior, fish that spent more time in the swimming zone spent more time actively swimming, however, swimming behavior was inconsistent across the time of the study. All relationships between swimming variables and exploration tests were relatively weak, though novel tank diving test variables had stronger correlations. Machine learning showed that three novel tank diving variables (entries top/bottom, movement rate, average top entry duration) and one open field variable (proportion of time spent frozen) were the best predictors of swimming behavior, demonstrating that the novel tank diving test is a powerful tool to investigate exploration. Increased knowledge about how individual differences in exploration may play a role in swimming behavior in zebrafish is fundamental to their utility as a model of exercise physiology and behavior.

Individual differences in stop-related activity are inflated by the adaptive algorithm in the stop signal task.

Research using the Stop Signal Task employing an adaptive algorithm to accommodate individual differences often report inferior performance on the task in individuals with ADHD, OCD, and substance use disorders compared to non-clinical controls. Furthermore, individuals with deficits in inhibitory control tend to show reduced neural activity in key inhibitory regions during successful stopping. However, the adaptive algorithm systematically introduces performance-related differences in objective task difficulty that may influence the estimation of individual differences in stop-related neural activity. This report examines the effect that these algorithm-related differences have on the measurement of neural activity during the stop signal task. We compared two groups of subjects (n = 210) who differed in inhibitory ability using both a standard fMRI analysis and an analysis that resampled trials to remove the objective task difficulty confound. The results show that objective task difficulty influences the magnitude of between-group differences and that controlling for difficulty attenuates stop-related activity differences between superior and poor inhibitors. Specifically, group differences in the right inferior frontal gyrus, right middle occipital gyrus, and left inferior frontal gyrus are diminished when differences in objective task difficulty are controlled for. Also, when objective task difficulty effects are exaggerated, group differences in stop related activity emerge in other regions of the stopping network. The implications of these effects for how we interpret individual differences in activity levels are discussed.

Predicting CYP2D6 phenotype from resting brain perfusion images by gradient boosting

The cytochrome P450 enzyme 2D6 is involved in the metabolism of 20% of all commonly used drugs, including many psychotropic drugs and CNS-active substances. CYP2D6 is among the CYP enzymes with the highest expression levels in the brain, suggesting a role in the local brain metabolism of psychotropic drugs and the existence of endogenous substrates. The genetic polymorphism of CYP2D6, which causes individual differences in activity levels of the enzyme, has also been characterized functionally in human brain imaging studies. Here we explore the feasibility of predicting CYP2D6 phenotype using component-wise gradient boosting on fMRI resting brain perfusion images. The images belonged to subjects showing a range of genetic CYP2D6 variants. We achieved sensitivity and specificity values between 85% and 87% for the classification of ultrarapid metabolisers, and between 71% and 79% for poor metabolisers. An extension of the boosting algorithm, developed to improve the clinical plausibility of the inherently sparse models, produced enhanced models in agreement with the results of previous studies, showing some brain regions as positively associated with genotypic variation, most prominently in the prefrontal white matter and the corpus callosum. With further development, such a probabilistic method might constitute a valuable, non-invasive alternative to actual genotyping.

Individual differences in activity levels in zebrafish (Danio rerio)

Individual differences and variation in behavioral responses have been identified in many animal species. These differences may be the result of genetic or environmental factors or the interaction between them. Analysis of individual differences in behavior may be important for many reasons. The zebrafish is a powerful model organism that is rapidly gaining popularity in behavioral brain research. However, individual differences have rarely been explored in zebrafish although significant variation in their performance has been reported. In the current study we identified individual differences in activity levels of zebrafish using a genetically heterogeneous population. Groups of zebrafish classified as high, medium, or low activity performers demonstrated consistent activity levels over a period of 7 days, and also in a subsequent open field task, suggesting stable individual differences as opposed to stochastic variation among subjects. We also uncovered a sex dependent relationship between behavioral measures. Female zebrafish in the high activity group preferred the top portion of the tank, whereas low activity females preferred the lower portion but males did not show such a relationship. The relationship between these two behaviors in females implies the potential existence of a behavioral syndrome persisting between contexts. Furthermore, females demonstrated a higher level of consistency in their behavior as compared to males, and the behavioral differences were found to be independent of both body size and weight of the tested subjects. The identification of individual differences in activity levels in zebrafish will allow the investigation of underlying genetic and/or environmental underpinnings.

Mink with Divergent Activity Levels have Divergent Reproductive Strategies

AbstractStable individual differences in activity levels within populations have been linked to differences in reproductive rate or parental care in several species, including American mink (Neovison vison). Fur‐farmed mink are good models for studying such effects because they yield large sample sizes and readily allow investigations into maternal behaviour, reproductive success, offspring performance and the relationships between these factors. On farms, very inactive individuals generally have smaller litters, and this held true in our study populations. We tested two competing hypotheses to explain this: (1) inactive individuals are failing to cope with a challenging environment and experiencing chronic stress and/or depression‐like ‘apathy’; this predicts female‐skewed litters, poorer maternal care, higher infant mortality and poorer infant growth and (2) inactive individuals do not have reduced fitness but instead employ an alternative adaptive reproductive strategy, trading off offspring quantity for quality; this predicts enhanced maternal care, reduced infant mortality and enhanced infant growth. Inactive females’ kits, especially their sons, grew faster than active females’, even after statistically controlling for litter size; and by 21 d, inactive and active dams’ litters no longer differed in total biomass, despite the former’s smaller litter sizes. In kit retrieval tests, inactive females were faster than active dams to reach their sons (as well as more likely to contact their sons than their daughters: a bias towards male kits not evident in the active dams). Furthermore, kit growth rates and dam latencies to touch them co‐varied, suggesting the existence of consistent differences in maternal style across inactive and active dams. Hypothesis 2 was thus supported: inactive females favour offspring quality over quantity, investing more resources in fewer kits, particularly males. This potentially boosts their sons’ adult fitness. More broadly for laboratory‐based studies, possible ‘captivity effects’ on the fitness correlates of activity and other personality traits are discussed.

Individual variation in temporal activity patterns in open-field tests

The open-field test, which measures animal activity or distance covered by individuals subjected to a novel arena, is used frequently in behaviour studies. Studies generally report consistent individual differences in activity level in the open-field, but no study has tested whether individuals change their activity level differently within a single open-field test. If such differences exist, then the reliability of activity levels measured over the whole test may be affected by the duration of the test. Here, we present analyses showing how a reaction norm approach can be used to account for individual differences in temporal activity patterns. Specifically, we measured individual temporal patterns of activity in wild eastern chipmunks, Tamias striatus, and house mouse, Mus musculus, strains by decomposing the total duration of open-field tests into successive shorter time intervals. Open-field tests on chipmunks and mice lasted 3 min and 5 min, respectively. We detected repeatable individual and strain differences in temporal activity patterns. Activity during the first time interval (at the beginning of the test) was positively correlated with activity measured over the whole test, meaning that short tests yield a valid measure of activity in chipmunks and mice. We recommend analysing open-field data using random regressions to obtain activity measurements that are robust against differences in temporal activity patterns.

Genetic influences on activity level in early childhood: do situations matter?

Although genetic influences on individual differences in activity level (AL) are well documented, few studies have considered the etiology of AL from a contextual perspective. In the present study, cross-situational and context-specific genetic effects on individual differences in AL at age 2 were examined. The AL of 312 twin pairs (144 monozygotic and 168 dzygotic) was mechanically assessed with actigraphs in the home and in laboratory test and play situations. AL displayed significant genetic variance in all 3 situations. Moreover, actigraph scores significantly correlated across situations. Multivariate genetic model-fitting analyses found that the observed cross-situational continuity in AL was due entirely to genetic factors. Situational differences in AL arise from genetic, shared environmental, and nonshared environmental influences.

Exposure to environmental enrichment elicits differential hippocampal cell proliferation: Role of individual responsiveness to anxiety

Environmental enrichment (EE) is a largely employed behavioral procedure in which animals are exposed to high stimulation compared with conventional housing conditions. Animal exposure to an EE exerts beneficial effects on the performance of different learning tasks and induces a number of behavioral, neurochemical, and neuroanatomical changes including hippocampal cell proliferation. However, the importance of voluntary interaction with the environment in these changes has not been clearly resolved yet. Moreover, the effects of a complex environment on animal emotionality still remains questionable and has not been explored in detail under conditions that allow unmasking individual responses among subjects in a group. The present study was aimed at exposing groups of rats to an EE, and analyzing individual differences in activity levels during EE sessions. We observed differences with respect to the activity level displayed by rats during the enriched sessions, which correlated with differences in the rate of hippocampal cell proliferation. It is suggested that exposure to EE may reduce anxiety-like behaviors and may elicit individual differences on emotional reactions positively linked with hippocampal neurogenesis and testosterone levels.

Evidence for a genetic etiology in hyperactivity in children.

There has been considerable controversy over the nosology of hyperactivity and attention deficit hyperactivity disorder (ADHD). There have been suggestions that genetic influences may play a role in the origins of individual differences on this dimension or dimensions of behavior and that an understanding of the significance of genetic factors might help to clarify the classification of these disorders. Multiple regression is used to analyze data from a sample of 91 pairs of identical twins and 105 pairs of same sex fraternal twins. The heritability of extreme group membership (h2g = 0.75) was significant for activity rated by the mother. The heritability for one of the measures of attention deficit was also significant (h2g = 0.76). The results are consistent with a significant genetic contribution to individual differences in activity levels and attention abilities.

Activity Level across the Menstrual Cycle

7 women recorded number of miles walked per day and oral temperature daily upon rising for 6 weeks. Analysis of variance indicated no significant differences in activity level associated with cycle phases but individual differences in activity level among subjects were significant.

Personality and genetic similarity theory

This article advances two theoretical schemas. The first concerns nomothetic human personality traits. We provide evidence that personality traits (a) exist, (b) are longitudinally stable, (c) can be assessed by several converging indices, (d) are inherited, and (e) have adaptive significance. We provide a review of some data on the inheritance of individual differences in activity level, aggression, altruism, chronogenetics, criminality, dominance, emotionality, intelligence, locus of control, political attitudes, sexuality, sociability, values, and vocational interests. We also suggest ways in which personality traits could arise in accordance with established genetic principles. p]The second half of the paper presents genetic similarity theory (GST). Going beyond kin selection, GST states that a gene may ensure its own survival by acting so as to bring about the reproduction of any organism in which copies of itself are to be found. An organism may have a tendency to exhibit favoritism toward genetically similar strangers as well as toward its own relatives. We order several data sets with this theory including (a) kin recognition studies in animals, (b) assortative mating, (c) intrafamilial relations, (d) human friendship and altruism, and (e) ethnic nepotism. We discuss a strong and weak version of GST and offer some predictions for future research.