Existence Of Interindividual Differences Research Articles

Stress, anxiety, and depression trajectories during the "first wave" of the COVID-19 pandemic: what drives resilient, adaptive and maladaptive responses in the Portuguese population?

The COVID-19 outbreak and the community mitigation strategies implemented to reduce new SARS-CoV-2 infections can be regarded as powerful stressors with negative consequences on people's mental health. Although it has been shown that negative emotional symptoms subside during lockdown, it is likely the existence of inter-individual differences in stress, anxiety and depression trajectories throughout lockdown. We aimed to cluster participants' according to their trajectories of stress, anxiety and depression scores throughout lockdown, and identify the sociodemographic, clinical, and lifestyle factors that may distinguish the subjects included in the different clusters. From March 23, 2020, to May 31, 2020, participants completed weekly online questionnaires on sociodemographic information (age, sex, education level, and employment status), psychological functioning (DASS-21, NEO-FFI-20), and clinical data (psychiatric disorders, psychiatric medication, physical disorders). Data regarding smoking status, alcohol consumption, physical activity, and time spent daily looking for COVID-19-related information were also collected. Stress, anxiety and depression trajectories were determined using latent class mixed models. A total of 2040 participants answered the survey at baseline and 603 participants answered all surveys. Three groups ("Resilient," "Recovered," and "Maladaptive") with distinct mental health trajectories were identified. Younger participants, women, participants with lower education level, not working, studying, diagnosed with a mental disorder, taking psychiatric medication, smokers, those who spent more time consuming COVID-19-related information and those with higher neuroticism tended to cluster in the "Maladaptive" group, placing them at higher risk of persistent negative emotional symptoms during compulsory confinement. Accordingly, a tailored approach to emotional suffering for vulnerable subjects during the COVID-19 and future pandemics must be devised.

Role of medial premotor areas in action language processing in relation to motor skills

The literature reports that the supplementary motor area (SMA) and pre-supplementary motor area (pre-SMA) are involved in motor planning and execution, and in motor-related cognitive functions such as motor imagery. However, their specific role in action language processing remains unclear. In the present study, we investigated the impact of repetitive transcranial magnetic stimulation (rTMS) over SMA and pre-SMA during an action semantic analogy task (SAT) in relation with fine motor skills (i.e., manual dexterity) and motor imagery abilities in healthy non-expert adults. The impact of rTMS over SMA (but not pre-SMA) on reaction times (RT) during SAT was correlated with manual dexterity. Specifically, results show that rTMS over SMA modulated RT for those with lower dexterity skills. Our results therefore demonstrate a causal involvement of SMA in action language processing, as well as the existence of inter-individual differences in this involvement. We discuss these findings in light of neurolinguistic theories of language processing.

Persistent Auditory Hallucinations in a Sample of Schizophrenic Outpatients

Introduction About a third of patients with schizophrenia have persistent auditory verbal hallucinations resulting in persistent distress, functional disability, and frequent loss of behavioral control. Objectives To estimate the prevalence of persistent auditory hallucinations in a sample of schizophrenic patients, to specify their characteristics and to identify their clinical associated factors. Methods This was a cross-sectional, descriptive and analytical study carried-on 144 out-patients (101 men and 43 women, mean age 38.24 ± 10.58 years) followed for schizophrenia in the psychiatry department of the university hospital of Monastir. The assessment was consisted by the collect of epidemiological, clinical and therapeutic data and the use of the Hoffman's auditory hallucinations rating scale (AHRS), and the positive and negative symptoms scale (PANSS). Results The prevalence of persistent auditory hallucinations (score of the AHRS ≥ 5) was 40.3%. The total mean score on the AHRS was 10.7 ± 7.8 for all patients and 19.4 ± 7.7 for patients with persistent auditory hallucinations. The items of the AHRS with higher sub scores were the number, the influence and the reality of the voices. The clinical associated factors with persistent auditory hallucinations after multivariate analysis were the family history of physical illness, the absence of tobacco consumption, the hallucinatory onset of disorders, the notion of prior hospitalization and continuous course. Conclusion Our results support the multidimensional nature of auditory hallucinations and confirm the existence of interindividual differences in these hallucinations. Persistent auditory hallucinations were associated with poor prognosis, requiring more effective therapeutic strategies.

Personality and reproductive success in a high-fertility human population

The existence of interindividual differences in personality traits poses a challenge to evolutionary thinking. Although research on the ultimate consequences of personality differences in nonhuman animals has recently undergone a surge of interest, our understanding of whether and how personality influences reproductive decisions in humans has remained limited and informed primarily by modern societies with low mortality-fertility schedules. Taking an evolutionary approach, we use data from a contemporary polygynous high-fertility human population living in rural Senegal to investigate whether personality dimensions are associated with key life-history traits in humans, i.e., quantity and quality of offspring. We show that personality dimensions predict reproductive success differently in men and women in such societies and, in women, are associated with a trade-off between offspring quantity and quality. In women, neuroticism positively predicts the number of children, both between and within polygynous families. Furthermore, within the low social class, offspring quality (i.e., child nutritional status) decreases with a woman's neuroticism, indicating a reproductive trade-off between offspring quantity and quality. Consistent with this, maximal fitness is achieved by women at an intermediate neuroticism level. In men, extraversion was found to be a strong predictor of high social class and polygyny, with extraverted men producing more offspring than their introverted counterparts. These results have implications for the consideration of alternative adaptive hypotheses in the current debate on the maintenance of personality differences and the role of individual factors in fertility patterns in contemporary humans.

A statistical assessment on the stochastic relationship between biomarker concentrations and environmental exposures

Biological monitoring has gradually developed into a powerful tool in the identification and quantification of exposures to occupational and/or environmental hazards in environmental and occupational health studies. Aggregate individual exposure to pollutants and evidence for exploring dose-response relationship in the human bodies can be assessed through biomarker measurements. The existence of inter-individual differences among a study population, however, often hampers the relationship assessment between exposure and the biomarker. In this paper, a statistical random effects model identified from a simplified one-compartment pharmacokinetic model is applied to establish the dynamic relationship between a biomarker and its corresponding external exposure. This model avoids the complex parameter estimation problem encountered using a physiologically based pharmacokinetic (PBPK) model, and incorporates inter-individual variations often ignored in the usual regression approach. In addition, the relevant parameters for the generic kinetic process can be estimated directly. As a guideline for preliminary sampling strategy, tables of required sample sizes and the number of repeated measurements to achieve the desired statistical power and test efficiency are given. The currently established biological exposure indices (BEIs) for benzene and methyl chloroform are employed to illustrate the impact of inter- individual variations on the percentages of protection for workers exposed to the threshold limit value (TLV) of the corresponding chemical.

Early recognition of newborn goat kids by their mother: II. Auditory recognition and evidence of an individual acoustic signature in the neonate.

The vocal recognition of newborn kids by their mother at 2 days postpartum and the possible existence of interindividual differences in the voice structure of newborn kids were investigated in two separate studies. The ability of goats to discriminate between the bleats of their own versus an alien kid was tested at 2 days postpartum in mothers being prevented access to visual and olfactory cues from the young. Goats spent significantly more time on the side of the enclosure from which their own kid was bleating, looked in its direction for longer, and responded more frequently to the bleats of their own than to those of the alien kid (p < 0.05). In the second study, the sonograms of 13 kids, studied from Days 1 to 5, showed significant interindividual differences for the five variables taken into account and on each of the 5 days (duration of bleat, fundamental frequency, peak frequency, and numbers of segments and of harmonics). The potential for individual coding ranged between 1.1 and 4.1, indicating that for some variables variations between individuals were greater than intraindividual variations. Furthermore, when considering the five parameters together, the discriminating scores showed an average of 95% in the 78 combinations of any 2 kids for any given day. Finally, some significant intraindividual differences also were found between days, suggesting ontogenic changes in the characteristics of the kid's voice in early life. Therefore, mother goats are likely to recognize the vocalizations of their 48-hr-old kids, as they show sufficient interindividual variability to allow the existence of individual vocal signatures, even though some of the characteristics of the bleats change rapidly over time.

Interleukin-1-Induced Sickness Behavior Depends on Behavioral Lateralization in Mice

Neveu, P. J., R.-M. Bluthé, S. Liè GE, S. Moya, B. Michaud and R. Dantzer. Interleukin-1-induced sickness behavior depends on behavioral lateralization in mice. Physiol Behav 63(4) 587–590, 1998. Inter-individual differences in brain-immune interactions have been demonstrated previously in mice using lateralization as a behavioral trait of population heterogeneity. Lipopolysaccharide (LPS), which is known to induce neurochemical, neuroendocrine, and immune responses depending on lateralization, is also able to induce sickness behavior, via the production of interleukin-1 (IL-1). The objective of this study was to determine whether lateralization can influence the behavioral response to LPS and to IL-1. To test this hypothesis, adult female C3H mice, previously selected for paw preference in a food reaching task, were injected intraperitoneally (i.p.) with 0.75 μg LPS or 0.75 μg recombinant IL-1β. Sickness induced by these molecules was measured by depressed social behavior, increased immobility, loss of body weight, and reduced food intake during the 6 h following injection. LPS-induced sickness was similar in right- and left-pawed mice. In contrast, IL-1-induced sickness behavior was dependent on behavioral lateralization. IL-1-induced depression of social investigation was more pronounced in right-pawed mice than in left-pawed animals. Likewise, IL-1-induced immobility was more important in right-pawed mice. There was a similar trend for food intake to be lower and loss of body weight to be higher in right-pawed mice than in left-pawed animals. These results demonstrate that right-pawed mice are more sensitive to IL-1-induced sickness than left-pawed animals. They extend our previous data showing a greater susceptibility to stress of right-pawed animals. The existence of inter-individual differences in the reactivity to stress or immune activation may be useful to study the mechanisms of the various strategies used by an individual in response to environmental aggressions.

RELATIONSHIPS BETWEEN BASIC EMOTIONS AND REPRODUCTIVE FITNESS ARE MODERATED BY SEX AS AN INTERNAL STATE

One of the key features of personality is the existence of inter-individual differences in motivation, emotions and behavior. Individual differences may be maintained in a population if personality traits are linked to states – conditions which affect the fitness-related outcomes of personality. We tested this assumption using the participants' sex as an internal state. Personality was operationalized via basic emotional systems: FEAR, ANGER, SADNESS, SEEKING, PLAYFULNESS and CARE. We measured several fitness-related outcomes like reproductive success, residual reproductive value, reproductive timing, the onset of sexual activity and short- term mating frequency. The data were collected in a community sample via an online study (N = 635; Mage = 29.4; 69.4% females). We used linear regression to predict fitness-related outcomes by basic emotions and tested interactions between sex and emotions to the prediction of these criteria measures. Predictable sex differences in basic emotions were obtained: males had lower scores on CARE, FEAR and SADNESS traits. Findings also showed that basic emotions can have an adaptive role in a biological sense – this was particularly true for CARE and ANGER traits. Finally, five interactions were detected, which showed that the adaptive benefits of emotional traits are different for males and females in a conceptually expected manner. Research results showed that personality traits operationalized as basic emotional systems can contribute to evolutionary fitness. These results furthermore expand the knowledge of human personality as a state-dependent behavior.