Effects of stressful life events on human brain structure: a longitudinal voxel-based morphometry study

Although stressful life events (SLEs) have been associated with an increased risk of illness and mental disorder, their impact on brain anatomy remains poorly understood. Using a longitudinal design, we tested the hypothesis that SLEs are significantly associated with changes in gray matter volume (GMV) in brain regions previously implicated in post-traumatic stress disorder (PTSD) in a group of clinically healthy adults. Magnetic resonance imaging was used to acquire an anatomical scan from 26 subjects (13 males and 13 females; mean age ± SD: 25.2 ± 4.3 years), with no psychiatric diagnosis, at two time points with a 3-month interval. Voxel-based morphometry was used to examine an association between SLEs and gray matter changes during this period. The number of SLEs was associated with a decrease in GMV in the anterior cingulate, hippocampus, and parahippocampal gyrus (p < 0.001). In contrast, there were no areas where the number of SLEs was associated with an increase in GMV. These results provide evidence that, in adults with no formal psychiatric diagnosis, SLEs are associated with GMV decreases in a subset of regions implicated in PTSD, and that these alterations can be observed within a period as short as 3 months.     

Online professionalism: social media, social contracts, trust, and medicine

The AMA Council on Ethical and Judicial Affairs (CEJA) has initiated an important discussion on medical professionalism and the use of social media by issuing thoughtful and practical guidance for physicians and medical students. The implications of online activities for trust in the profession, as well as for trust between patient and doctor, however, will need further exploration as digital life expands and evolves.     

Global and local vision in natural scene identification

The results of previous studies have suggested that to optimize the decoding of visual information, global contents of a scene are analyzed before local features (global precedence hypothesis). Evidence supporting this hypothesis has been provided for identification of characters, faces, hybrid stimuli, and simple objects. In the present study, we examined identification of high- and low-pass filtered natural pictures. Despite the radical differences in the type of information conveyed by global and local features, confident and accurate identification was achieved on the basis of either kind of information when an intermediate range of spatial frequencies was preserved. The present data are consistent with the notion of global precedence in scene identification.     

Conflict adaptation in time: Foreperiods as contextual cues for attentional adjustment

Interference evoked by distractor stimulus information, such as flankers in the Eriksen task, is reduced when the proportion of conflicting stimuli is increased. This modulation is sensitive to contextual cues such as stimulus location or color, suggesting attentional adjustment to conflict contingencies on the basis of context information. In the present study, we explored whether conflict adjustment is modulated by temporal variation of conflict likelihood. To this end, we associated low and high proportions of conflict stimuli with foreperiods of different lengths. Flanker interference was higher with foreperiods associated with low conflict proportions, suggesting that participants use the foreperiod as a contextual cue for attentional adjustment. We conjecture that participants initially adopt the strategy useful for conflict contingencies associated with short foreperiods, and then readjust during the trial, in the absence of any additional exogenous cue, when the imperative stimulus has not occurred during a certain time interval.     

Activity experiences shape perceived fitness trajectories: results from a 6-month randomized controlled trial in older women

In this study we addressed the subjective benefits of activity interventions that were designed to improve cognitive fitness in old age. Two hundred and fifty-nine women (aged 70-93 years) were randomized to participate in an exercise or a computer course or a control condition for 6 months. Subjective ratings of the perceived change of cognitive and physical fitness components were captured before, during, after the intervention interval, and at a 10-month follow-up. Positive and negative affect levels and objective cognitive fitness parameters served as possible covariates. Multilevel modeling revealed that the computer group rated memory and concentration as having improved at 4 months and again at 6 months. The exercise group, in contrast, perceived physical capacities as maintained or improved. The characteristics of the activity experience seem to determine the perceived fitness changes. We conclude that actual learning experiences improve one's self-concept of abilities.     

Engaging in cultural activities compensates for educational differences in cognitive abilities

The goal of the current project was to examine whether engagement in intellectual/cultural activities explains the long-term effects of education on cognitive abilities throughout adulthood, and whether it compensates for educational differences in cognitive abilities throughout adulthood. Participants between 18 and 96 years of age completed a comprehensive questionnaire about intellectual/cultural activities that they participated in and performed a wide variety of cognitive tests. There were no mediation effects of engagement in intellectual/cultural activities on the relationship between education and cognitive functioning. In contrast, engagement in intellectual/cultural activities was found to moderate the relations between education and the level of fluid ability, working memory, speed of processing, and episodic memory. Findings suggest that the risk of cognitive decline in people with less education can be reduced via engagement in intellectual and cultural activities throughout adulthood.     

Relative versus absolute standards for everyday risk in adolescent HIV prevention trials: expanding the debate

The concept of minimal risk has been used to regulate and limit participation by adolescents in clinical trials. It can be understood as setting an absolute standard of what risks are considered minimal or it can be interpreted as relative to the actual risks faced by members of the host community for the trial. While commentators have almost universally opposed a relative interpretation of the environmental risks faced by potential adolescent trial participants, we argue that the ethical concerns against the relative standard may not be as convincing as these commentators believe. Our aim is to present the case for a relative standard of environmental risk in order to open a debate on this subject. We conclude by discussing how a relative standard of environmental risk could be defended in the specific case of an HIV vaccine trial among adolescents in South Africa.     

The specificity of temporal expectancy: evidence from a variable foreperiod paradigm

In speeded choice tasks with variable foreperiods (FPs), individuals behaviourally adapt to various frequency manipulations. Adaptations have been shown to frequencies of different stimulus-response events, to frequencies of different foreperiods, and to frequencies of different event-foreperiod combinations. We have investigated how participants adapt to a situation where all three frequency manipulations are done simultaneously. Three variable foreperiod experiments are reported. In Experiment 1, one target (the peak distributed target) appeared particularly frequently after one particular FP (the peak foreperiod), while another target was less frequent and equally distributed over all foreperiods. In Experiment 2, the equally distributed target was overall more frequent than the peak distributed one. In both experiments, performance advantages for the peak distributed target were specific to the peak foreperiod, and performance advantages at the peak foreperiod were specific to the peak distributed targets. A third experiment showed that, when two differently frequent target are both equally distributed over FPs, the performance distribution over FPs is not significantly different between both targets. Together, the results suggest that participants were able to simultaneously and specifically adapt to frequency manipulations in events, foreperiods, and event-foreperiod combinations.     

Grammatical gender in German: a case for linguistic relativity?

The "principle of linguistic relativity" holds that, by way of grammatical categorization, language affects the conceptual representations of its speakers. Formal gender systems are a case in point, albeit a particularly controversial one: Previous studies obtained broadly diverging data, thus giving rise to conflicting conclusions. To a large extent, this incoherence is related to task differences and methodological problems. Here, a priming design is presented that avoids previous problems, as it prevents participants from employing gender information in a strategic manner. Four experiments with German native speakers show priming effects of the prime's grammatical gender on animate and nonanimate targets, an effect for the prime's biological gender on animate targets, but no effect for the prime's biological gender on nonanimate targets, and thus speak against an effect of language on thought for German gender.     

Effects of spatial compatibility on integration processes in graph comprehension

A precondition for efficiently understanding and memorizing graphs is the integration of all relevant graph elements and their meaning. In the present study, we analyzed integration processes by manipulating the spatial compatibility between elements in the data region and the legend. In Experiment 1, participants judged whether bar graphs depicting either statistical main effects or interactions correspond to previously presented statements. In Experiments 2 and 3, the same was tested with line graphs of varying complexity. In Experiment 4, participants memorized line graphs for a subsequent validation task. Throughout the experiments, eye movements were recorded. The results indicated that data-legend compatibility reduced the time needed to understand graphs, as well as the time needed to retrieve relevant graph information from memory. These advantages went hand in hand with a decrease of gaze transitions between the data region and the legend, indicating that data-legend compatibility decreases the difficulty of integration processes.