Effects Of Individual Differences Research Articles

Hormonal contraceptive influences on cognition and psychopathology: Past methods, present inferences, and future directions

In the last decade, there has been a remarkable surge in research on the neural and behavioral correlates of hormonal contraceptive use, particularly oral contraceptive use. Questions have evolved swiftly and notably, with studies no longer revealing if hormonal contraceptives matter for the brain and behavior, but rather how, when, and for whom they matter most. Paralleling this shift, the goal of this review is to move beyond an average synthesis of hormonal contraceptive influences on human cognition and psychopathology (and their neural substrates) in order to consider the nature and specificity of effects. Accompanied by an evaluation of study methods and informed by findings from animal models, this consideration uncovers promising areas of research in the next ten years, including potential activational and organizational effects of hormonal contraceptive use, individual differences in effects that matter for the wellbeing of unique individuals, and correlates of intrauterine device use.

Menstrual Cycle-Driven and Day-to-Day Changes in Sexual Desire

ABSTRACT Introduction Although research has attempted to quantify the effects of the menstrual cycle on sexual desire, we lack a clear understanding of how the menstrual cycle, and the many physical and psychological changes of the menstrual cycle, are related to changes in sexual desire. For example, whereas evolutionary theories predict that women should converge on increased sexual interest around ovulation, methodologically strong tests of this idea are lacking, and there is reason to hypothesize that there are significant individual differences in these associations. Objective This study has three main objectives. First, to quantify the contributions of (a) mean-level differences across individuals, (b) average effects of the menstrual cycle, and (c) individual differences in the effects of the menstrual cycle, to sexual desire. Second, to test for the influence of day-to-day changes in physical and psychological symptoms on day-to-day changes in sexual desire, independent of the menstrual cycle. Third, to test for associations between cyclical changes in physical and psychological symptoms attributable to the menstrual cycle and cyclical changes in sexual desire attributable to the menstrual cycle. Methods A sample of n = 213 university-aged women with regular menstrual cycles, who were not using hormonal birth control, completed daily questionnaires for two full menstrual cycles (M = 58 daily reports per participant). Measurement included changes in sexual desire (increase and decrease), as well as physical (headaches, back and joint pain, cramps, breast changes) and psychological changes (anxiety, depression, happiness, mood swings, low energy) that are commonly associated with the menstrual cycle. Multilevel modeling with random intercepts and slopes, as well as linear regression of cosine coefficients of all physical and psychological symptom scores, were used to test these hypotheses. Results Relative to the three objectives described above, results showed that: mean-level differences across participants accounted for 21.5% of the overall variance in changes in sexual desire; the average/fixed effects of the menstrual cycle accounted for 1.6% of the variance; and random effects of the menstrual cycle (e.g., individual differences in menstrual cycle effects) accounted for 7.8% of the variance. Only day-to-day changes in psychological symptoms, but not day-to-day changes in physical symptoms, were associated with day-to-day changes in sexual desire (independent of the menstrual cycle). Finally, only menstrual cycle-related cyclical changes in depression were associated with menstrual cycle-related changes in sexual desire. Conclusions Results from the present study demonstrate that average effects of the menstrual cycle play a very small role in influencing changes in sexual desire (see left panel of Figure 1). Most variance in changes in sexual desire, instead, is explained by individual differences in mean levels, and in individual differences in the effects of the menstrual cycle (see right panel in Figure 1). Thus, women differ significantly in their average levels of desire and how the menstrual cycle influences changes in their desire. Moreover, only psychological symptoms, and not physical symptoms, are associated with changes in sexual desire. Of the psychological symptoms, happiness is the most strongly associated with changes in sexual desire. Disclosure Any of the authors act as a consultant, employee or shareholder of an industry for: ApexNeuro

Effects of Transcranial Direct Current Stimulation on Attentional Bias to Methamphetamine Cues and Its Association With EEG-Derived Functional Brain Network Topology.

Although transcranial direct current stimulation (tDCS) has shown to potentially mitigate drug craving and attentional bias to drug-related stimuli, individual differences in such modulatory effects of tDCS are less understood. In this study, we aimed to investigate a source of the inter-subject variability in the tDCS effects that can be useful for tDCS-based treatments of individuals with methamphetamine (MA) use disorder (IMUD). Forty-two IMUD (all male) were randomly assigned to receive a single-session of either sham or real bilateral tDCS (anodal right/cathodal left) over the dorsolateral prefrontal cortex. The tDCS effect on MA craving and biased attention to drug stimuli were investigated by quantifying EEG-derived P3 (a measure of initial attentional bias) and late positive potential (LPP; a measure of sustained motivated attention) elicited by these stimuli. To assess the association of changes in P3 and LPP with brain connectivity network (BCN) topology, the correlation between topology metrics, specifically those related to the efficiency of information processing, and the tDCS effect was investigated. The P3 amplitude significantly decreased following the tDCS session, whereas the amplitudes increased in the sham group. The changes in P3 amplitudes were significantly correlated with communication efficiency measured by BCN topology metrics (r = -0.47, P = .03; r = -0.49, P = .02). There was no significant change in LPP amplitude due to the tDCS application. These findings validate that tDCS mitigates initial attentional bias, but not the sustained motivated attention, to MA stimuli. Importantly, however, results also show that the individual differences in the effects of tDCS may be underpinned by communication efficiency of the BCN topology, and therefore, these BCN topology metrics may have the potential to robustly predict the effectiveness of tDCS-based interventions on MA craving and attentional bias to MA stimuli among IMUD.

Individual differences in the effects of the ACTION-PAC intervention: an application of personalized medicine in the prevention and treatment of obesity.

There is an increased interest in the use of personalized medicine approaches in the prevention or treatment of obesity, however, few studies have used these approaches to identify individual differences in treatment effects. The current study demonstrates the use of the predicted individual treatment effects framework to test for individual differences in the effects of the ACTION-PAC intervention, which targeted the treatment and prevention of obesity in a high school setting. We show how methods for personalized medicine can be used to test for significant individual differences in responses to an intervention and we discuss the potential and limitations of these methods. In our example, 25% of students in the preventive intervention, were predicted to have their BMI z-score reduced by 0.39 or greater, while at other end of the spectrum, 25% were predicted to have their BMI z-score increased by 0.09 or more. In this paper, we demonstrate and discuss the process of using methods for personalized medicine with interventions targeting adiposity and discuss the lessons learned from this application. Ultimately, these methods have the potential to be useful for clinicians and clients in choosing between treatment options, however they are limited in their ability to help researchers understand the mechanisms underlying these predictions.

Personalized approach to antipsychotic-induced weight gain prognosis

Abstract: Antipsychotics (APs) are the base of schizophrenia pharmacotherapy. There are large individual differences in effectiveness and adverse drug reactions (ADRs) of APs. There is an urgent need for a personalized approach to the therapy. Genetic factors are predisposed to patient's response to APs therapy. Pharmacogenetic studies of APs have examined a number of single nucleotide variants (SNVs), of which only a few were associated with therapeutic efficacy and ADRs development. However, only a limited number of these results have clinical applications in psychiatry. Nowadays, it seems promising to study SNVs of leptin system genes (LEP, LEPR) and neuropeptide Y (NRY). Studying the mechanisms of APs-induced weight growth will allow their transmission to a personalized approach. It will help psychiatrists in patients’ selection for the APs therapy. This will increase safety and effectiveness of the therapy, improve the quality of life and adherence to therapy in patients with schizophrenia.

Individual differences in the psychological effects of forest sounds based on type A and type B behavior patterns

Studies on the psychological effects of nature have been increasing, but few studies have focused on individual differences in these effects. The purpose of this study was to examine the individual differences in the psychological effects of forest sounds based on Type A and Type B behavior patterns. The Kwansei Gakuin (KG) daily life questionnaire was used as an indicator for Type A and Type B behavior patterns. This study included 29 female university students (mean age, 22.3 ± 2.1 years) who were exposed to high-resolution forest and city sounds for 60 s, and they provided subjective evaluations on a modified Semantic Differential method and the Profile of Mood States questionnaire. After exposure to the forest sounds, the Type A group (n = 12) reported higher levels of feeling comfortable, relaxed, and natural, as well as lower levels of anger–hostility, than the Type B group (n = 17). The findings demonstrated that the Type A and Type B groups experienced different psychological effects from forest-derived auditory stimulation.

Ovarian hormones: a long overlooked but critical contributor to cognitive brain structures and function.

Cognitive neuroscience research has traditionally overlooked half of the population. Arguing that variability in ovarian hormones confounds empirical findings, girls and women have been excluded from research for decades. But times are changing. This review summarizes historical trends that have led to a knowledge gap in the role of ovarian hormones in neuroscience, synthesizes recent findings on ovarian hormone contributions to cognitive brain structures and function, and highlights areas ripe for future work. This is accomplished by reviewing research that has leveraged natural experiments in humans across the life span that focus on puberty, the menstrual cycle, hormonal contraceptive use, menopause, and menopausal hormone therapy. Although findings must be considered in light of study designs (e.g., sample characteristics and group comparisons versus randomized crossover trials), across natural experiments there is consistent evidence for associations of estradiol with cortical thickness, especially in frontal regions, and hippocampal volumes, as well as with frontal regions during cognitive processing. There are also emerging investigations of resting state connectivity and progesterone along with exciting opportunities for future work, particularly concerning biopsychosocial moderators of and individual differences in effects in novel natural experiments. Thus, delineating complex ovarian hormone contributions to cognitive brain structures and function will advance neuroscience.

Individual Differences in Effects of Muscular Endurance Training under Hyperoxic Condition

Individual Differences in Effects of Muscular Endurance Training under Hyperoxic Condition

Impact of Genetic Variation on Stress-Related Ethanol Consumption.

The effect of stress on alcohol consumption in humans is highly variable, and the underlying processes are not yet understood. Attempts to model a positive relationship between stress and increased ethanol (EtOH) consumption in animals have been only modestly successful. Our hypothesis is that individual differences in stress effects on EtOH consumption are mediated by genetics. We measured alcohol consumption, using the drinking-in-the-dark (DID) paradigm in females from 2 inbred mouse strains, C57BL/6J (B6) and DBA/2J (D2), and 35 of their inbred progeny (the BXD family). A control group was maintained in normal housing and a stress group was exposed to chronic mild stress (CMS), consisting of unpredictable stressors over 7weeks. These included predator, social, and environmental perturbations. Alcohol intake was measured over 16weeks in both groups during baseline (preceding 5-week period), CMS (intervening 7-week period), and post-CMS (final 4-week period). We detected a strong effect of CMS on alcohol intake. A few strains demonstrated CMS-related increased alcohol consumption; however, most showed decreased intake. We identified 1 nearly significant quantitative trait locus on chromosome 5 that contains the neuronal nitric oxide synthase gene (Nos1). The expression of Nos1 is frequently changed following alcohol exposure, and variants in this gene segregating among the BXD population may modulate alcohol intake in response to stress. The results we present here represent the first study to combine chronic stress and alcohol consumption in a genetic reference population of mice. Differences in susceptibility to the effects of stressful environments vis-à-vis alcohol use disorders would suggest that the differences have at least some basis in genetic constitution. We have also nominated a likely candidate gene underlying the large individual differences in effects of stress on alcohol consumption.

Predictors of individual performance changes related to item positions in PISA assessments

BackgroundItem position effects have been a common concern in large-scale assessments as changing the order of items in booklets may have an undesired effect on test performance. If every test taker would be affected by the effect in the very same way, comparisons between groups of individuals would still be valid. However, research has shown that in addition to a general fixed effect of item positions, the extent of the effect varies considerably across individuals. These individual differences are referred to as persistence. Test takers with a high level of persistence are able to keep up their performance better throughout the test administration, whereas those with a lower level of persistence show a larger decline in their test performance.MethodsThe present study applied a multilevel extended item response theory (IRT) framework and used the data from the PISA 2006 science, 2009 reading, and 2012 mathematics assessments. The first objective of this study is to provide a systematic investigation of item position effects across the three PISA domains, partially replicating the previous studies on PISA 2006 and 2009. Second, this study aims to gain a better understanding of the nature of individual differences in position effects by relating them to student characteristics. Gender, socio-economic status, language spoken at home, and three motivational scales (enjoyment of doing the subject being assessed, effort thermometer, perseverance) were used as person covariates for persistence.ResultsThis study replicated and extended the results found in previous studies. An overall negative item cluster position effect and significant individual differences in this effect were found in all the countries in the three PISA domains. Furthermore, the most frequently observed effect of person covariates on persistence is gender, with girls keeping up their performance better than boys. Other predictors showed little or inconsistent effects on persistence.ConclusionsOur study demonstrated inter-individual differences as well as group differences in item position effects, which may threaten the comparability between persons and groups. The consequences and implications of item position effects and persistence for the interpretation of PISA results are discussed.

Estimating the distribution of welfare effects using quantiles

SummaryThis paper proposes a framework to model welfare effects that are associated with a price change in a population of heterogeneous consumers. The framework is similar to that of Hausman and Newey (Econometrica, 1995, 63, 1445–1476), but allows for more general forms of heterogeneity. Individual demands are characterized by a general model that is nonparametric in the regressors, as well as monotonic in unobserved heterogeneity, allowing us to identify the distribution of welfare effects. We first argue why a decision maker should care about this distribution. Then we establish constructive identification, propose a sample counterparts estimator, and analyze its large‐sample properties. Finally, we apply all concepts to measuring the heterogeneous effect of a change of gasoline price using US consumer data and find very substantial differences in individual effects across quantiles.

Differences between biological and chronological age‐at‐death in human skeletal remains: A change of perspective

This analysis seeks to determine whether differences between real and estimated chronological age (CA) with biological age (BA) in skeletal individuals reflect variability in aging. A total of 87 individuals of two samples, ranging from 20 to 94 years old, were analyzed. One, partially documented, belongs to a Mexican skeletal collection dating to the 20th century; the other is an assemblage of prehispanic individuals from different archaeological sites. In all specimens, the tooth annulation method (TCA) was applied to estimate CA, while-excluding individuals older than 80 years-auricular surface (AS) and pubic symphysis (PS) methods were used to estimate BA. Statistical analyses were conducted to identify correlations and significance of the differences between CA vs. TCA, CA vs. AS/PS, TCA vs. AS/PS. Sex of individuals was assessed for its influence in aging. The use of TCA to estimate CA was successful for most individuals. A strong correlation was found between CA vs. TCA, CA vs. AS/PS, TCA vs. AS/PS and their differences were significant but variation in these were found when assessed by separate age groups. Sex did not influence such differences. TCA can be used to estimate CA and its differences with BA, being less than 10 years, are similar to those found in living populations. Differences between CA and BA are due to intra-population variability, which could be the consequence of individual differences in aging. More research is needed to have confidence that under- and overestimations of BA are indicators of aging variability at the level of the individual.

Effects of emotion regulation strategies on music-elicited emotions: An experimental study explaining individual differences

This experimental study examined if emotional experience can be manipulated by applying an emotion regulation strategy during music listening and if individual differences in effects of strategies can be explained by person characteristics. Adults (N=466) completed questionnaires and rated emotions. They were randomly assigned to a condition, in which they applied an emotion regulation strategy (suppression, enhancement, neutral) when listening to a music fragment. Next, participants rated emotions again. MANCOVA showed that individuals who applied enhancement experienced the strongest increase in emotion intensity. Age, neuroticism, extraversion, and positive trait affect predicted individual differences in effects of enhancement and suppression, e.g., especially more neurotic and introverted individuals experienced increased emotion intensity when applying enhancement. This study shows that emotional experience can be intensified by music listening, which can be facilitated by applying enhancement. Applying an emotion regulation strategy during music listening seems especially effective when it matches person characteristics.

AM fungi patchiness and the clonal growth of Glechoma hederacea in heterogeneous environments.

The effect of AM fungi spatial distribution on individual plant development may determine the dynamics of the whole plant community. We investigated whether clonal plants display, like for other resources, a foraging or a specialization response, to adapt to the distribution of AM fungi. Two separate experiments were done to investigate the response of Glechoma hederacea to a heterogeneous distribution of a mixture of 3 AM fungi species, and the effects of each species on colonization and allocation traits. No specialization and a limited foraging response to the heterogeneous distribution of AM fungi was observed. An effect of the AM fungal species on plant mass allocation and ramet production, but not on spacer length, was detected. Two possible explanations are proposed: (i) the plant’s responses are buffered by differences in individual effects of the fungal species or their root colonization intensity. (ii) the initial heterogeneous distribution of AM fungi is perceived as homogeneous by the plant either by reduced physiological integration or due to the transfer of AM fungi propagules through the stolons. Microscopic and DNA sequencing analyses provided evidence of this transfer, thus demonstrating the role of stolons as dispersal vectors of AM fungi within the plant clonal network.

It’s the power of food: individual differences in food cue responsiveness and snacking in everyday life

BackgroundDiscretionary eating behaviour (“snacking”) is dependent on internal and external cues. Individual differences in the effects of these cues suggest that some people are more or less likely to snack in certain situations than others. Previous research is limited to laboratory-based experiments or survey-based food recall. This study for the first time examines everyday snacking using real-time assessment, and examines whether individual differences in cue effects on snacking can be explained by the Power of Food scale (PFS).MethodsEcological Momentary Assessment (EMA) study with 53 non-clinical participants over an average of 10 days. Multiple daily assessments: Participants reported every snack and responded to randomly timed surveys during the day. Internal and external cues were measured during both types of assessment. Demographic data and PFS scores were assessed during a baseline lab visit. Data were analysed using multilevel linear and multilevel logistic regression with random intercepts and random slopes as well as cross-level interactions with PFS scores.ResultsHigher individual PFS scores were associated with more daily snacking on average (B = 0.05, 95 % CI = 0.02,0.08, p < .001). More average daily snacking was associated with higher BMI (B = 1.42, 95 % CI = 0.19,2.65, p = .02). Cue effects (negative affect, arousal, activities, company) on snacking were significantly moderated by PFS: People with higher PFS were more likely to snack when experiencing negative affect, high arousal, engaging in activities, and being alone compared to people with lower PFS scores.ConclusionsPFS scores moderate the effects of snacking cues on everyday discretionary food choices. This puts people with higher PFS at higher risk for potentially unhealthy and obesogenic eating behaviour.

Individual differences in effect of school-based cognitive training on academic achievement

Individual differences in effect of school-based cognitive training on academic achievement

Individual differences in effects of child care quality: The role of child affective self-regulation and gender

The current study investigated whether the relation between child care quality and children's socio-emotional behavior depended on children's affective self-regulation skills and gender. Participants were 545 children (Mage=27 months) from 60 center-based child care centers in the Netherlands. Multi-level analyses showed that children with low affective self-regulation skills or who were male demonstrated less teacher-rated social competence when exposed to relatively low quality child care. In addition, children with low affective self-regulation skills also showed more social competence in the case of relatively high quality child care, suggesting mechanisms of differential susceptibility. No main effects of child care quality or interactions were found for teacher- and parent-rated externalizing behavior. These findings emphasize the importance of considering children's affective self-regulation skills and gender in understanding the effects of child care quality. High quality child care can be a means to strengthen children's social development.

Post-illumination pupil response after blue light: Reliability of optimized melanopsin-based phototransduction assessment

Melanopsin-containing retinal ganglion cells have recently been shown highly relevant to the non-image forming effects of light, through their direct projections on brain circuits that regulate alertness, mood and circadian rhythms. A quantitative assessment of functionality of the melanopsin-signaling pathway could be highly relevant in order to mechanistically understand individual differences in the effects of light on these regulatory systems. We here propose and validate a reliable quantification of the melanopsin-dependent Post-Illumination Pupil Response (PIPR) after blue light, and evaluated its sensitivity to dark adaptation, time of day, body posture, and light exposure history. Pupil diameter of the left eye was continuously measured during a series of light exposures to the right eye, of which the pupil was dilated using tropicamide 0.5%. The light exposure paradigm consisted of the following five consecutive blocks of five minutes: baseline dark; monochromatic red light (peak wavelength: 630 nm, luminance: 375 cd/m2) to maximize the effect of subsequent blue light; dark; monochromatic blue light (peak wavelength: 470 nm, luminance: 375 cd/m2); and post-blue dark. PIPR was quantified as the difference between baseline dark pupil diameter and post-blue dark pupil diameter (PIPR-mm). In addition, a relative PIPR was calculated by dividing PIPR by baseline pupil diameter (PIPR-%). In total 54 PIPR assessments were obtained in 25 healthy young adults (10 males, mean age ± SD: 26.9 ± 4.0 yr). From repeated measurements on two consecutive days in 15 of the 25 participants (6 males, mean age ± SD: 27.8 ± 4.3 yrs) test–retest reliability of both PIPR outcome parameters was calculated. In the presence of considerable between-subject differences, both outcome parameters had very high test–retest reliability: Cronbach's α > 0.90 and Intraclass Correlation Coefficient > 0.85. In 12 of the 25 participants (6 males, mean age ± SD: 26.5 ± 3.6 yr) we examined the potential confounding effects of dark adaptation, time of the day (morning vs. afternoon), body posture (upright vs. supine position), and 24-h environmental light history on the PIPR assessment. Mixed effect regression models were used to analyze these possible confounders. A supine position caused larger PIPR-mm (β = 0.29 mm, SE = 0.10, p = 0.01) and PIPR-% (β = 4.34%, SE = 1.69, p = 0.02), which was due to an increase in baseline dark pupil diameter; this finding is of relevance for studies requiring a supine posture, as in functional Magnetic Resonance Imaging, constant routine protocols, and bed-ridden patients. There were no effects of dark adaptation, time of day, and light history. In conclusion, the presented method provides a reliable and robust assessment of the PIPR to allow for studies on individual differences in melanopsin-based phototransduction and effects of interventions.

Linking inter-individual differences in the perceptual load effect to spontaneous brain activity.

Previous researches have widely demonstrated that the interference from peripheral distractor will decrease when the task load is high. However, no study to date has paid attention to the individual differences in perceptual load effect (PLE) and little is known of spontaneous brain activity associated with PLE during resting state. To investigate this issue, we used resting-state functional Magnetic Resonance Imaging (fMRI) to examine the relationship between the amplitude of low-frequency fluctuations (ALFFs) and PLE. The results showed that there were large individual differences in PLE and we found PLE was significantly associated with ALFFs in left inferior temporal gyrus (ITG) and left precentral/postcentral gyrus. The present study suggested that the PLE was measurable, and there were individual differences in this effect. Moreover, these results implicated that: 1) mutual competition for limited capacity, which is involved in visual attention, and 2) response control that is included in behavior response both may contribute to the modulation induced by perceptual load.

Individual Differences in Effects of Light on Circadian Rhythm and Melatonin Secretion(&lt;Feature&gt;Indoor Lighting at Night Taking Effect of Light on Circadian Rhythm into Consideration)

Individual Differences in Effects of Light on Circadian Rhythm and Melatonin Secretion(&lt;Feature&gt;Indoor Lighting at Night Taking Effect of Light on Circadian Rhythm into Consideration)