Using a virtual reality system to study balance and walking in a virtual outdoor environment: a pilot study.

Falls and fall-related injuries are a major problem for elderly persons. Most falls occur during walking and turning, and the risk of falling increases when attention is diverted to something besides walking. It is often difficult to standardize methods for testing balance and fall tendency in a clinically relevant setting. We describe the development of a system using a virtual environment (VE) to assess how attention demanding and unexpected events influence a person's capacity to control balance and movement. The hardware in the system consists of a head-mounted display (HMD), a magnetic tracker system, and two SGI computers. The software consists of the image generation of the VE and the management and visualization of motion tracking data. In a preliminary pilot study eight subjects (age 23-80) participated. Each subject walked on a normal floor and was visually presented a familiar outdoor environment in the HMD. They were exposed to different unexpected events, such as a virtual snowfall and tilting of the VE. Disturbances of balance and walking patterns such as changes in speed, stride length and balance reactions like slipping were observed. Two subjects experienced symptoms of cyber sickness with a SSQ score above 25 points. Walking with sensors only did not affect walking time, but in VE the subjects generally walked more slowly. Virtual tilting of the environment had an impact on balance performance during walking. This effect was not observed while the test subjects were walking in a virtual snowfall. The model needs further development but may hold a potential for clinical use.     

Neural correlates of variable working memory load across adult age and skill: dissociative patterns within the fronto-parietal network

We examined neural changes related to variations in working memory load by using an n -back task with three levels and functional magnetic resonance imaging. Younger adults were divided into high- and low-performing groups (Young-High; Young-Low) and compared with older adults. Relative to Young-High, capacity-constraints in working memory were apparent between load 1–2 for the elderly and between load 2–3 for Young-Low. Capacity-constraints in neural activity followed this pattern by showing a monotonically increasing response in parietal cortex and thalamus for Young-High, whereas activity leveled off at 1-back for the elderly and at 2-back for Young-Low. The response in dorsal frontal cortex followed a similar pattern with the addition that the magnitude of activation differed within capacity limitations (Old > Young at 1-back; Young-Low > Young-High at 2-back). These findings indicate that an important determinant of WM capacity is the ability to keep the frontal cortex adequately engaged in relation to current task demands.     

The Grossarth-Maticek and Eysenck Personality Types,Health-related behaviour,and indicators of transitory ill-health

The aim of this study was to scrutinize the relationship between personality type as described by Grossarth-Maticek and Eysenck, health-related behaviours, and indicators of transitory ill health in a community sample. The sample consisted of all per sons aged 40 years (45 men and 35 women) in a Swedish municipality who agreed to take part in a health examination at the primary health care centre of the municipality. The Short Interpersonal Reactions Inventory (Grossarth-Maticek and Eysenck, 1990) was used to measure personality type. Self-report data were obtained regarding seven health-related behaviours. Health was assessed in three ways; self-report (paper and pencil), self-report (interview response to physician), and measures of 36 biological variables including immune system indicators. The allocation of persons to the different personality types proved problematic using the established methods. By combining the types, according to Eysenck's personality model, and performing a cluster analysis on this combination, a ‘healthy’ and a ‘stressed’ profile were identified within both the male and the female group of subjects. Persons in the healthy personality cluster showed more favourable scores on the health-related behaviour indices and on the self-report health scales than the persons in the stressed cluster. They also tended to score lower than those in the stressed cluster on most of the biological markers known to increase during acute stress. The possibility that this implies a higher level of strain for the persons in the stressed cluster on various bodily systems is discussed.     

Brain activation during episodic memory retrieval: sex differences

Behavioral studies have shown a tendency for women to outperform men on episodic memory tasks. Here, data from a series of positron emission tomography (PET) studies were analyzed to examine sex differences in brain activity associated with episodic memory retrieval (yes/no recognition). A total of 17 women and 17 men were included in the analyses. The strongest effect of the design was a retrieval-related increase in activity, involving right prefrontal and anterior cingulate regions, that was common to women and men. In addition, a significant task-by-sex interaction effect was observed which involved a distributed set of brain regions, including several frontal areas. These results suggest that while the neural correlate of episodic memory retrieval is largely the same for men and women, some differences do exist. Possible explanations for the observed differences are discussed, and it is concluded that biological and experiential factors jointly contribute to sex differences in brain activity.     

Brain activation while forming memories of fearful and neutral faces in women and men

Event-related functional MRI (fMRI) was used to assess brain activity during encoding of fearful and neutral faces in 12 women and 12 men. In a subsequent memory analysis, the authors separated successful from unsuccessful encoding of both types of faces, based on whether they were remembered or forgotten in a later recognition memory test. Overall, women and men recruited overlapping neural circuitries. Both sexes activated right-sided medial-temporal regions during successful encoding of fearful faces. Successful encoding of neutral faces was associated with left-sided lateral prefrontal and right-sided superior frontal activation in both sexes. In women, relatively greater encoding related activity for neutral faces was seen in the superior parietal and parahippocampal cortices. By contrast, men activated the left and right superior/middle frontal cortex more than women during successful encoding of the same neutral faces. These findings suggest that women and men use similar neural networks to encode facial information, with only subtle sex differences observed for neutral faces.     

Levels of processing: A view from functional brain imaging

This paper briefly reviews two central assumptions of the levels-of-processing framework in the light of findings from recent PET and fMRI studies: First, to address the suggestion that memory traces can be seen as records of analyses carried out for the purposes of perception and comprehension, studies on encoding-retrieval overlap in brain activation patterns are considered. Second, to address the suggestion that deeper, more semantic, processing results in more durable traces, studies of how encoding activity relates to processing depth and subsequent memory performance are examined. The results show that some of the sensory regions that are activated during initial perception are subsequently reactivated during retrieval, and activity in frontal and medial-temporal brain regions is related to depth of processing and level of memory performance. Collectively, these results provide support for central components of the levels framework.     

Cognitive deficits in relation to personality type and hypothalamic-pituitary-adrenal (HPA) axis dysfunction in women with stress-related exhaustion

Exhaustion caused by long-term work-related stress may cause cognitive dysfunction. We explored factors that may link chronic stress and cognitive impairment. Personality, psychiatric screening, and behavior were assessed by self-reporting measures in 20 female patients (mean age 39.3 years; range 26-53) with a preliminary diagnosis of stress-related exhaustion and in 16 healthy matched controls. Cognitive performance was investigated with a detailed neuropsychological test battery. Cortisol axis function was assessed by urinary and saliva collections of cortisol, dexamethasone suppression, Synacthen response, and corticotropin-releasing hormone (CRH) tests. Proinflammatory cytokines were measured. Hippocampal volumes were estimated by magnetic resonance imaging. Multivariate and univariate statistical methods were used to explore putative differences between groups and factors linked to cognitive impairment. Cognitive function clearly differed between groups, with decreased attention and visuospatial memory in the patient group, suggesting frontal cortex/medial temporal cortex-network dysfunction. Increased harm avoidance and persistence was present among patients, with lowered self-directedness linked to lower quality of life, increased anxious and depressive tendencies, and experiences of psychosocial stress. Attention was decreased with concomitantly impaired visuospatial memory. The pituitary (adrenocorticotropic hormone, ACTH) response to CRH was decreased in patients, with an increased cortisol/ACTH response to CRH. However, cortisol production rates, diurnal or dexamethasone-suppressed saliva cortisol levels, and the cortisol response to Synacthen were unaltered. Hippocampal volumes did not differ between groups. These findings suggest that cognitive dysfunction in stress-related exhaustion is linked to distinct personality traits, low quality of life, and a decreased ACTH response to CRH.     

Low social inclusion in childhood: adjustment and early predictors

The principal aim of the present study was to obtain a deeper understanding than hitherto of the concurrent correlates and prospective predictors of loneliness and poor peer acceptance, both falling under the umbrella term low social inclusion. Problematic and socially competent behaviours were investigated as possible predictors of low social inclusion in grade 6, as defined by self‐rated loneliness and degree of peer non‐acceptance, respectively. In grade 6 808 children participated whereof 323 were followed longitudinally from first grade. Loneliness in grade 6 was distinctively associated with high levels of internalizing problems, concurrently as well as prospectively. Peer acceptance, on the other hand, emerged as a complex, multifaceted aspect, with concurrent, independent predictions from both externalizing and internalizing problem behaviours as well as social competence, although prospective analyses found early externalizing problems to be the strongest predictor of peer acceptance. Moderating effects of social competence were sparse, although peer nominated social competence buffered peer acceptance for children with high levels of aggression in the concurrent analyses and social competence boosted peer acceptance for children with low problem levels in the predictive analyses. Social competence did not appear to buffer the negative impact of early problem behaviours on peer relations. Copyright © 2008 John Wiley & Sons, Ltd.     

How well do measures of inhibition and other executive functions discriminate between children with ADHD and controls?

The aim of the present study was to evaluate the usefulness of Barkley's (1997a) model of inhibition and executive functioning in describing the deficits associated with Attention Deficit Hyperactivity Disorder (ADHD). Besides group differences, the present study addressed the question of independent effects of inhibition and the other executive functions in discriminating between children with ADHD and controls and how well, in terms of sensitivity and specificity, these measures can classify the children into the correct group. The results showed that children with ADHD differed significantly from controls with regard to measures of inhibition as well as all other executive function measures, except repetition of hand movements. In logistic regression models, three different measures tapping inhibition, working memory and emotion regulation were shown to be significant independent predictors of group membership. The sensitivity for these three variables as a set was 76.2, the specificity was 90.5, with a total of 86% of the sample correctly classified. When excluding the parental rating of emotion regulation, the overall classification rate decreased some, but was still relatively high in comparison with previous studies within this area of research.     

Incidental retrieval processes influence explicit test performance with data-limited cues

In two experiments, the influence of incidental retrieval processes on explicit test performance was tested. In Experiment 1, subjects studied words under four conditions (auditory-shallow, auditory-deep, visual-shallow, and visual-deep). One group of subjects received auditory and visual word-fragment completion; another group received auditory and visual word-fragment cued recall. Results indicated that changes in sensory modality between study and test reduced both recall and priming performances; levels of processing significantly affected only the cued recall test. These results indicated that incidental retrieval processes might affect explicit test performance when retrieval cues are data limited. Experiment 2 supported this conclusion by showing an effect of matching study and test modalities on explicit test performance with fragment but not with copy cues. Taken together, these results support Roediger and McDermott’s (1993) suggestion that explicit test performance is influenced by incidental retrieval processes when data-limited retrieval cues are used.