Investigation of visual space using an exocentric pointing task

Classically, it has been assumed that visual space can be represented by a metric. This means that the distance between points and the angle between lines can be uniquely defined. However, this assumption has never been tested. Also, measurements outdoors, where monocular cues are abundant, conflict with this model. This paper reports on two experiments in which the structure of visual space was investigated, using an exocentric pointing task. In the first experiment, we measured the influence of the separation between pointer and target and of the orientation of the stimuli with respect to the observer. This was done both monocularly and binocularly. It was found that the deviation of the pointer settings depended linearly on the orientation, indicating that visual space is anisotropic. The deviations for configurations that were symmetrical in the median plane were approximately the same, indicating that left/right symmetry was maintained. The results for monocular and binocular conditions were very different, which indicates that stereopsis was an important cue. In both conditions, there were large deviations from the veridical. In the second experiment, the relative distance of the pointer and the target with respect to the observer was varied in both the monocular and the binocular conditions. The relative distance turned out to be the main parameter for the ranges used (1-5 m). Any distance function must have an expanding and a compressing part in order to describe the data. In the binocular case, the results were much more consistent than in the monocular case and had a smaller standard deviation. Nevertheless, the systematic mispointings remained large. It can therefore be concluded that stereopsis improves space perception but does not improve veridicality.     

Consistent haptic feedback is required but it is not enough for natural reaching to virtual cylinders

In virtual reality it is easy to control the visual cues that tell us about an object's shape. However, it is much harder to provide realistic virtual haptic feedback when grasping virtual objects. In this study we examined the role of haptic feedback when grasping (virtual) cylinders with an elliptical circumference. In Experiment 1 we placed the same circular cylinder at the simulated location of virtual elliptical cylinders of varying shape, so that the haptic feedback did not change when the visually specified shape changed. We found that the scaling of maximum grip aperture with the diameter of the nearest principal axis (.14+/-.04) was much weaker than when grasping real cylinders (.54+/-.04, Cuijpers, Brenner, & Smeets, 2006 Grasping reveals visual misjudgements of shape. Experimental Brain Research, 175, 32-44). For the scaling of grip orientation with the orientation of the cylinder we found large individual differences: the range is .07-.82 (average .42+/-.07) as compared to .55-.79 (average .67+/-.03) for grasping real cylinders. In Experiment 2 we provided consistent haptic feedback by placing real cylinders that matched the location, shape and orientation of the virtual cylinders. The scaling gains of both maximum grip aperture (.39+/-.04) and grip orientation (.56+/-.08) were substantially higher than in Experiment 1, but still lower than for grasps to real cylinders. The variability between participants for the scaling of grip orientation was also much reduced. These results showed that although haptic feedback must be consistent with visual information, it is not sufficient for natural prehension. We discuss the implications of these findings in terms of the integration of visual information with haptic feedback.     

Competitive Memory Training for treating depression and rumination in depressed older adults: a randomized controlled trial

Although rumination is an important mediator of depressive symptoms, there is insufficient proof that an intervention that specifically targets rumination ameliorates the clinical condition of, depressed patients. This study investigates whether a time-limited cognitive behavioral intervention (Competitive Memory Training, or COMET for depressive rumination) is an effective treatment for depression and rumination. This intervention was tested in older adult depressed outpatients. A total of 93 patients (aged ≥65 years with major depression and suffering from rumination) were treated in small groups according to the COMET protocol in addition to their regular treatment. Patients were randomized to two treatment conditions: 7 weeks of COMET + treatment-as-usual (TAU) versus TAU only. COMET + TAU showed a significant improvement in depression and rumination compared with TAU alone. This study shows that the transdiagnostic COMET protocol for depressive rumination might also be successful in treating depression and rumination in older adults.     

Changes in Behaviour and Body Weight Following a Single or Double Social Defeat in Rats

In a series of experiments, the consequences of a single and double social conflict on various behaviours and body weight in rats were studied. Animals were subjected to social defeat by placing them into the territory of an aggressive male conspecific for one hour, either once, or twice at the same time on two consecutive days. To assess the consequences of social defeat, three experiments were performed with independent groups of rats. In the first experiment, an open field test was performed two days after the last conflict. Locomotor activity was strongly reduced after social defeat. There were no differences between the single and double defeat group. To assess the effects of social defeat on subsequent social behaviour, a second experiment was performed in which experimental animals were confronted with an unfamiliar non-aggressive rat two days after a single or double conflict. Social defeat resulted in a reduction of social contact with the unfamiliar conspecific. There was no difference between the single and double conflict group. In the third experiment, the effects of social conflict on food intake, body weight and saccharine preference were measured. Food intake was not affected after a single conflict, but in the double conflict group food intake was decreased for several days. Body weight gain was decreased after both single and double social defeat. The decrease was stronger in the double conflict group. Water intake and saccharine preference were not significantly affected. This study revealed that social defeat in rats causes pronounced changes in various behaviours and body weight. Different aspects of behaviour are differentially affected by defeat with respect to the magnitude and time course of the changes induced. Moreover, different behavioural parameters are differentially sensitive to repetition of the stressor.     

Who benefits from psychotherapies for adult depression? A meta-analytic update of the evidence

It is not clear whether specific target groups for psychotherapies in adult depression benefit as much from these treatments as other patients. We examined target groups that have been examined in randomized trials, including women, older adults, students, minorities, patients with general medical disorders, and specific types of depression, and we examined where patients were recruited. We conducted subgroup and multivariate metaregression analyses in a sample of 256 trials (with 332 comparisons) comparing psychotherapy with an inactive control condition. Only 22% of the studies had low risk of bias (RoB), heterogeneity was high and there was a considerable risk of publication bias. A meta-regression analysis among low RoB studies showed that effect sizes found for studies among women, older adults, patients with general medical disorders, patients recruited from primary care, and patients scoring above a cut-off on a self-rating depression scale, did not differ significantly from effect sizes from other studies. For other target groups, the number of low RoB studies was too small to draw any conclusion. We found few indications that psychotherapies for adult depression are more or less effective in women, older adults, patients with comorbid general medical disorders, and primary care patients.     

Eye movement desensitization and reprocessing for mental health problems: a systematic review and meta-analysis

ABSTRACT

There is no comprehensive meta-analysis of randomised trials examining the effects of Eye Movement Desensitization and Reprocessing (EMDR) on post-traumatic stress disorder (PTSD) and no systematic review at all of the effects of EMDR on other mental health problems. We conducted a systematic review and meta-analysis of 76 trials. Most trials examined the effects on PTSD (62%). The effect size of EMDR compared to control conditions was g = 0.93 (95% CI: 0.67–.18), with high heterogeneity (I²= 72%). Only four of 27 studies had low risk of bias, and there were indications for publication bias. EMDR was more effective than other therapies (g = 0.36; 95% CI: 0.14–0.57), but not in studies with low risk of bias. Significant results were also found for EMDR in phobias and test anxiety, but the number of studies was small and risk of bias was high. EMDR was examined in several other mental health problems, but for none of these problems, sufficient studies were available to pool outcomes. EMDR may be effective in the treatment of PTSD in the short term, but the quality of studies is too low to draw definite conclusions. There is not enough evidence to advise it for the use in other mental health problems.