Science posts

See science posts on page 7 below.

    • 2007
    • Martin Reuter et al.
    • Molecular genetics support Gray's personality theory: the interaction of COMT and DRD2 polymorphisms predicts the behavioural approach system
    • The present study provides the first direct molecular genetics support for Gray's Reinforcement Sensitivity Theory (RST), which is one of the most influential biologically oriented personality theories. It was investigated whether the DRD2 TaqIA and the COMT polymorphisms were related to the dimensions of Gray's personality theory, as measured by the Carver and White BIS/BAS scales. In a sample of 295 healthy subjects results revealed significant DRD2×COMT interactions (i.e. epistasis) for the total BAS scale (related to positive emotionality) and for the subscales Drive (D) and Fun Seeking (FS). High BAS scores were observed if the catabolic enzyme activity and the D2 receptor density as indicated by the two polymorphisms were in disequilibrium, i.e. in the presence of the Val−/A1− (low enzyme activity/high receptor density) or the Val+/A1+ (high enzyme activity/low receptor density) alleles. In a random subsample (n=48), it could be demonstrated that those allele ..
    • 2003
    • Erik G J├Ânsson et al.
    • Association between a promoter dopamine D2 receptor gene variant and the personality trait detachment
    • Background Personality traits have shown considerable heritable components. Striatal dopamine D2 receptor density, as determined by positron-emission tomography, has been associated with detached personality, as assessed by the Karolinska Scales of Personality. A putative functional promoter polymorphism in the dopamine D2 receptor gene (DRD2), –141C ins/del, has been associated with dopamine D2 receptor density. Methods In this study healthy subjects (n = 235) who filled in at least one of several personality questionnaires (Karolinska Scales of Personality, Swedish Universities Scales of Personality, Health-relevant Five-factor Personality Inventory, and Temperament and Character Inventory) were analyzed with regard to the DRD2 –141C ins/del variant. Results There was an association (p = .001) between the DRD2 –141C ins/del variant and Karolinska Scales of Personality Detachment scale, indicating higher scores in subjects with the –141C del varian..
    • 2001
    • Satomi Katsuragi et al.
    • Lack of association between a polymorphism in the promoter region of the dopamine D2 receptor and personality traits
    • Disturbances of the dopaminergic neurotransmitter system have been associated with a personality trait that involves novelty seeking. A functional polymorphism in the promoter region of the dopamine D2 receptor gene (DRD2) has been reported to be associated with schizophrenia. We examined the association between this polymorphism in the DRD2 promoter region and personality traits, as assessed with the Tridimensional Personality Questionnaire. No significant association emerged between the polymorphism in the DRD2 promoter region and personality traits. Entering sex and age as covariates in an analysis of covariance did not change the results. These data fail to confirm an association between a polymorphism in the promoter region of the DRD2 and personality traits.
    • 2000
    • Gebhardt, Ch et al.
    • Non-association of dopamine D4 and D2 receptor genes with personality in healthy individuals.
    • Recently, different research groups reported conflicting results with regard to an association of dopamine 4 receptor (DRD4) genotypes and the personality dimension of novelty seeking (NS). High scores for NS seemed to be associated with long alleles of a DRD4 polymorphism. Furthermore, an association between personality traits and the dopamine 2 (DRD2) receptor gene was reported. NS and persistence (PS) high scores seemed to be associated with alleles of DRD2. We examined 109 (78 female and 31 male) normal healthy individuals using Cloninger's Temperament and Character Inventory (TCI) in order to replicate these findings. We genotyped a 48 base pair variable number of tandem repeats (from two to eight repeats) polymorphism in the third exon of DRD4 and a Cys311Ser polymorphism in exon 7 of DRD2. We tested alleles and genotypes of DRD4 (allele 7 absent or present; genotype 4,4 versus 4,7), and Ser/Cys and Cys/Cys genotypes of DRD2 for associations with TCI values. NS and the alleles ..
    • 2008
    • Roshan Cools et al.
    • Working Memory Capacity Predicts Dopamine Synthesis Capacity in the Human Striatum
    • Evidence from psychopharmacological research has revealed that dopamine receptor agents have opposite effects on cognitive function depending on baseline levels of working memory capacity. These contrasting effects have been interpreted to reflect differential baseline levels of dopamine. Here we demonstrate for the first time that working memory capacity as measured by listening span predicts dopamine synthesis capacity in the striatum, indicating that subjects with low working memory capacity have low DA synthesis capacity in the striatum, whereas subjects with high working memory capacity have high DA synthesis capacity in the striatum.
    • 1986
    • McLean, James E. et al.
    • Multivariate Analysis of Ipsative Data: Problems and Solutions.
    • The term "ipsative" refers to measurement based on intra-individual comparisons. The research literature in the social sciences contains many cautions about using ipsative data in multivariate analysis. The purpose of this paper is to identify the problems associated with the multivariate and regression analyses of ipsative data and to provide recommendations for avoiding these problems. Ipsative scales have been mainly employed by researchers in the area of personality measurement, vocational choice, and the assessment of values and attitudes where the scale values are interrelated. Due to this interrelatedness of the scales, many problems can arise when multivariate and/or regression analysis procedures are used to analyze the data obtained from ipsative measurement. Such an analysis would produce a singular correlation or covariance matrix that cannot be inverted. The results of the analysis can be inflated or deflated relationships that are artifacts of the forc..
    • 1994
    • William P. Dunlap & John M. Cornwell
    • Factor Analysis of Ipsative Measures
    • lpsative measures are multiple measures, where the data are collected, or are modified, in such a way that all subject totals across the measures are equal. Much has been written about factor analysis with such data, however, no clear consensus has been reached regarding the suitability of ipsative measures for factor analysis. The purpose of the present article is to show analytically the fundamental problems that ipsative measures impose for factor analysis. The expected value of the correlation between ipsative measures is shown to equal - 1/ ( k - I), where k is the number of measures. The rank of the resulting correlation matrix is reduced by one to k - 1, and ipsativity alone produces k - 1 artifactual bipolar factors, which will obscure any actual interrelations among the measures. If the data are known to be ipsative or if the tell-tale signs of ipsativity are seen, factor analysis should not be done.
    • 2015
    • Arif A Hamid et al.
    • Mesolimbic dopamine signals the value of work
    • Dopamine cell firing can encode errors in reward prediction, providing a learning signal to guide future behavior. Yet dopamine is also a key modulator of motivation, invigorating current behavior. Existing theories propose that fast (phasic) dopamine fluctuations support learning, whereas much slower (tonic) dopamine changes are involved in motivation. We examined dopamine release in the nucleus accumbens across multiple time scales, using complementary microdialysis and voltammetric methods during adaptive decision-making. We found that minute-by-minute dopamine levels covaried with reward rate and motivational vigor. Second-by-second dopamine release encoded an estimate of temporally discounted future reward (a value function). Changing dopamine immediately altered willingness to work and reinforced preceding action choices by encoding temporal-difference reward prediction errors. Our results indicate that dopamine conveys a single, rapidly evolving decision variable, the availabl..
    • 2005
    • Thatcher RW, et al.
    • EEG and intelligence: relations between EEG coherence, EEG phase delay and power.
    • OBJECTIVE: There are two inter-related categories of EEG measurement: 1, EEG currents or power and; 2, EEG network properties such as coherence and phase delays. The purpose of this study was to compare the ability of these two different categories of EEG measurement to predict performance on the Weschler Intelligence test (WISC-R). METHODS: Resting eyes closed EEG was recorded from 19 scalp locations with a linked ears reference from 442 subjects aged 5-52 years. The Weschler Intelligence test was administered to the same subjects but not while the EEG was recorded. Subjects were divided into high IQ (> or = 120) and low IQ (< or = 90) groups. EEG variables at P<.05 were entered into a factor analysis and then the single highest loading variable on each factor was entered into a discriminant analysis where groups were high IQ vs. low.Q. RESULTS: Discriminant analysis of high vs. low IQ was 92.81-97.14% accurate. Discriminant scores of intermediate IQ subjects (i.e. ..
    • 2007
    • Peper JS et al.
    • Genetic influences on human brain structure: a review of brain imaging studies in twins.
    • Twin studies suggest that variation in human brain volume is genetically influenced. The genes involved in human brain volume variation are still largely unknown, but several candidate genes have been suggested. An overview of structural Magnetic Resonance (brain) Imaging studies in twins is presented, which focuses on the influence of genetic factors on variation in healthy human brain volume. Twin studies have shown that genetic effects varied regionally within the brain, with high heritabilities of frontal lobe volumes (90-95%), moderate estimates in the hippocampus (40-69%), and environmental factors influencing several medial brain areas. High heritability estimates of brain structures were revealed for regional amounts of gray matter (density) in medial frontal cortex, Heschl's gyrus, and postcentral gyrus. In addition, moderate to high heritabilities for densities of Broca's area, anterior cingulate, hippocampus, amygdala, gray matter of the parahippocampal gyrus, and white ma..