Normal aging increases discriminal dispersion in visuospatial short-term memory

Computational models of cognitive aging propose that age-related decrements in cognitive performance, including short-term memory (STM), result from less distinct stimulus representations. When applied to visual STM, these models predict higher discriminal dispersion (L. L. Thurstone, 1927, Psychophysical analysis, The American Journal of Psychology, 38, 368-389.) in older adults than in younger adults. To test this prediction, we used a change-detection paradigm for visuospatial locations, with different levels of cognitive load (one, three, or five items) and retention interval (100 or 1,000 ms). Adult age differences were not reliable at Load 1, but were substantial at Loads 3 and 5. Effects of retention time did not differ across age groups, suggesting that age-related differences originated mainly from early processing stages. Applying a mixture model to the data revealed age-related increases in discriminal dispersion and decreases in asymptotic discrimination performance (indexing STM capacity). We concluded that age-related declines in discriminal dispersion, in addition to increasing capacity limitations, impair visual STM performance with advancing adult age. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

Brain activation patterns in major depressive disorder and work stress-related long-term sick leave among Swedish females

Deficits in executive functioning and working memory associated with frontal lobe dysfunction are prominent in depression and work-related long-term sick leave (LTSL). This study used functional magnetic resonance imaging (fMRI) to investigate potential differences in brain activation patterns in these conditions. In addition, the function of the hypothalamic-pituitary-adrenal (HPA) axis was examined and compared between groups. Since there is a clear overrepresentation of women in these diagnostic groups, and to ensure a more homogenous sample population, only women were included. To examine the neural correlates of relevant cognitive processes in patients on sick leave >90 days due to work-related LTSL, recently diagnosed patients with major depression Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV criteria, untreated), and healthy controls (n?=?10, each group), a 2-back working memory task and a visual long-term memory task were administered during fMRI scanning. HPA axis functioning was investigated using a diurnal curve of saliva cortisol and a dexamethasone suppression test. Task performance was comparable among the three groups. Multivariate image analysis revealed that both memory tasks engaged a similar brain network in all three groups, including the prefrontal and parietal cortex. During the 2-back task, LTSL patients had significant frontal hypoactivation compared to controls and patients with depression. Saliva cortisol measurements showed a flattening of the diurnal rythmicity in LTSL patients compared to patients with depression and healthy contols. Taken together, these findings indicate that work stress-related LTSL and major depression are dissociable in terms of frontal activation and diurnal cortisol rhythmicity.     

Emotion and perception of one's own actions--a comment on Wilke, Synofzik and Lindner

Wilke et al. (2012) make significant headway in gaining a better understanding of the influence affect cues may have on action perception and judgement. In our view their account also brings up a row of important questions demanding further research. This concerns (a) the role of conceptual and non-conceptual content and (b) the different effects emotions of the same valence may play in the perception and judgement of action.     

Psychometric properties of the Five Facets Mindfulness Questionnaire (FFMQ) in a meditating and a non-meditating sample

The factor structure, internal consistency, construct validity, and predictive validity of the Dutch version of the Five Facet Mindfulness Questionnaire (FFMQ-NL) were studied in a sample of meditators (n = 288) and nonmeditators (n = 451). A five-factor structure was demonstrated in both samples, and the FFMQ-NL and its subscales were shown to have good internal consistencies. Meditators scored higher on all facets of the FFMQ-NL than the participants in the nonmeditating sample. For both samples, expected negative correlations between most mindfulness facets (all except for the Observing facet) and the constructs of alexithymia, thought suppression, rumination, worry, and dissociation were found. The Observing facet of the FFMQ-NL showed an unexpected positive correlation with thought suppression in the nonmeditating sample. Furthermore, as expected, mindfulness facets were negatively related to psychological symptoms, and all mindfulness facets except for Observing and Describing significantly predicted psychological symptoms. Overall, the Dutch FFMQ demonstrated favorable psychometric properties, commensurate with its (original) English language version.     

The synergy of working memory and inhibitory control: behavioral, pharmacological and neural functional evidences

Concomitant deficits in working memory and behavioral inhibition in several psychiatric disorders like attention-deficit/hyperactivity disorder, addiction or mania, suggest that common brain mechanisms may underlie their etiologies. Based on the theoretical assumption that a continuum exists between health and mental disorders, we explored the relationship between working memory and inhibition in healthy individuals, through spontaneous inter individual differences in behavior, and tested the hypothesis of a functional link through the fronto-striatal dopaminergic system. Rats were classified into three groups, showing good, intermediate and poor working memory and were compared for their inhibitory abilities. These two functions were simultaneously modulated by a dose-effect of d-amphetamine and in situ hybridization was used to quantify dopaminergic receptor (RD1) mRNAs in prefrontal cortex and striatal areas. A functional relationship between working memory and inhibition abilities was revealed. Both functions were similarly modulated by d-amphetamine according to an inverted-U shaped relationship and depending on initial individual performances. D-amphetamine selectively improved working memory and inhibition of poor and intermediate performers at low doses whereas it impaired both processes in good performers at a higher dose. D1 receptors were less expressed in prelimbic, infralimbic and anterior cingulate cortices of good compared to intermediate and poor performers, whereas no difference was observed between groups in striatal areas. The synergy of working memory and inhibitory abilities, observed in both healthy and psychiatric populations, may originate from endogenous variability in dopaminergic prefrontal cortex activity. Such findings confirm the validity of a dimensional approach, based on the concept of continuity between health and mental disorders for identifying endophenotypes of mental disorders.     

A mixed model approach to meta-analysis of diagnostic studies with binary test outcome

We propose 2 related models for the meta-analysis of diagnostic tests. Both models are based on the bivariate normal distribution for transformed sensitivities and false-positive rates. Instead of using the logit as a transformation for these proportions, we employ the tα family of transformations that contains the log, logit, and (approximately) the complementary log. A likelihood ratio test for the cutoff value problem is developed, and summary receiver operating characteristic (SROC) curves are discussed. Worked examples showcase the methodology. We compare the models to the hierarchical SROC model, which in contrast employs a logit transformation. Data from various meta-analyses are reanalyzed, and the reanalysis indicates a better performance of the models based on the tα transformation. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

The influence of control and related variables on commuting stress

Existing research on commuting stress has shown that it is affected by variables such as control, predictability, the duration of the commute and impedance. The present study investigates the impact of several factors on the stress that commuters experience and clarifies possible relations between variables. For the purpose of this study, an online questionnaire was completed by 363 commuters of the Vienna region. The relative strength of the relationship between predictors and commuting stress was determined by multiple regression analysis. Results suggest that control is the most powerful predictor of commuting stress, followed by the duration of the commute, predictability and impedance. Control significantly interacts with the duration of the commute and predictability. Based on these findings a research model is proposed, clearly depicting the moderating impact of the duration of the commute and incorporating a clear distinction between predictability and control.     

Associative memory or algorithmic search: a comparative study on learning strategies of bats and shrews

Two common strategies for successful foraging are learning to associate specific sensory cues with patches of prey ("associative learning") and using set decision-making rules to systematically scan for prey ("algorithmic search"). We investigated whether an animal's life history affects which of these two foraging strategies it is likely to use. Natterer's bats (Myotis nattereri) have slow life-history traits and we predicted they would be more likely to use associative learning. Common shrews (Sorex araneus) have fast life-history traits and we predicted that they would rely more heavily on routine-based search. Apart from their marked differences in life-history traits, these two mammals are similar in body size, brain weight, habitat, and diet. We assessed foraging strategy, associative learning ability, and retention time with a four-arm maze; one arm contained a food reward and was marked with four sensory stimuli. Bats and shrews differed significantly in their foraging strategies. Most bats learned to associate the sensory stimuli with the reward and remembered this association over time. Most shrews searched the maze using consistent decision-making rules, but did not learn or remember the association. We discuss these results in terms of life-history traits and other key differences between these species. Our results suggest a link between an animal's life-history strategy and its use of associative learning.