PRP-paradigm provides evidence for a perceptual origin of the negative compatibility effect

Visual stimuli (primes) that are made invisible by masking can affect motor responses to a subsequent target stimulus. When a prime is followed by a mask which is followed by a target stimulus, an inverse priming effect (or negative compatibility effect) has been found: Responses are slow and frequently incorrect when prime and target stimuli are congruent, but fast and accurate when prime and target stimuli are incongruent. To functionally localize the origins of inverse priming effects, we applied the psychological refractory period (PRP-) paradigm which distinguishes a perceptual level, a central bottleneck, and a level of motor execution. Two dual-task experiments were run with the PRP-paradigm to localize the inverse priming effect relative to the central bottleneck. Together, results of the Effect-Absorption and the Effect-Propagation Procedure suggest that inverse priming effects are generated by perceptual mechanisms. We suggest two perceptual mechanisms as the source of inverse priming effects.     

Bidirectional plasticity in striatonigral synapses: a switch to balance direct and indirect basal ganglia pathways

There is no hypothesis to explain how direct and indirect basal ganglia (BG) pathways interact to reach a balance during the learning of motor procedures. Both pathways converge in the substantia nigra pars reticulata (SNr) carrying the result of striatal processing. Unfortunately, the mechanisms that regulate synaptic plasticity in striatonigral (direct pathway) synapses are not known. Here, we used electrophysiological techniques to describe dopamine D(1)-receptor-mediated facilitation in striatonigral synapses in the context of its interaction with glutamatergic inputs, probably coming from the subthalamic nucleus (STN) (indirect pathway) and describe a striatonigral cannabinoid-dependent long-term synaptic depression (LTD). It is shown that striatonigral afferents exhibit D(1)-receptor-mediated facilitation of synaptic transmission when NMDA receptors are inactive, a phenomenon that changes to cannabinoid-dependent LTD when NMDA receptors are active. This interaction makes SNr neurons become coincidence-detector switching ports: When inactive, NMDA receptors lead to a dopamine-dependent enhancement of direct pathway output, theoretically facilitating movement. When active, NMDA receptors result in LTD of the same synapses, thus decreasing movement. We propose that SNr neurons, working as logical gates, tune the motor system to establish a balance between both BG pathways, enabling the system to choose appropriate synergies for movement learning and postural support.     

Time limits and gender differences on paper-and-pencil tests of mental rotation: a meta-analysis

The purpose of this study was to summarize research relevant to the influence of time limits on gender differences in paper-and-pencil tasks of mental rotation by means of a meta-analysis. Thirty-six effect sizes from published and unpublished studies examining the influence of time constraints were retrieved. Results showed that gender differences in mental rotation are significantly larger when the task is administered with time constraints compared to when such constraints are absent. In addition, the magnitude of gender differences was linearly related to the amount of time available for test completion. These findings were not related to the age or the year of birth of participants in the retrieved studies. The results are discussed with regard to their implications for explanations of gender differences in mental rotation and cognitive abilities in general.     

The response order effect: People believe the first person who remembers an event

When groups of people remember an event, the order in which they discuss their memories is important. In three experiments, a response order effect was shown in which participants believed the first speaker to be more accurate and more confident than a subsequent speaker. Further, participants were more likely to report as their own memory what the first speaker reported than what a subsequent speaker reported. The experiments showed that the response order effect was not due to intrinsic characteristics of what the first speaker said. Even when participants chose the response order themselves and the speakers’ dialogue was counterbalanced, participants still believed that the first speaker was more accurate and confident than a subsequent speaker. Because in most situations the person who introduces a particular topic into a discussion is more accurate, people may assume that this is true, even when the response order is random.     

HIV and depression--a systematic review of interventions

HIV-positive individuals are more likely to be diagnosed with major depressive disorder than HIV-negative individuals. Depression can precede diagnosis and be associated with risk factors for infection. The experience of illness can also exacerbate depressive episodes and depression can be a side effect to treatment. A systematic understanding of which interventions have been tested in and are effective with HIV-seropositive individuals is needed. This review aims to provide a comprehensive understanding of evaluated interventions related to HIV and depression and provide some insight on questions of prevalence and measurement. Standard systematic research methods were used to gather quality published papers on HIV and depression. From the search, 1015 articles were generated and hand searched resulting in 90 studies meeting adequacy inclusion criteria for analysis. Of these, 67 (74.4%) were implemented in North America (the US and Canada) and 14 (15.5%) in Europe, with little representation from Africa, Asia and South America. Sixty-five (65.5%) studies recruited only men or mostly men, of which 31 (35%) recruited gay or bisexual men. Prevalence rates of depression ranged from 0 to 80%; measures were diverse and rarely adopted the same cut-off points. Twenty-one standardized instruments were used to measure depression. Ninety-nine interventions were investigated. The interventions were diverse and could broadly be categorized into psychological, psychotropic, psychosocial, physical, HIV-specific health psychology interventions and HIV treatment-related interventions. Psychological interventions were particularly effective and in particular interventions that incorporated a cognitive-behavioural component. Psychotropic and HIV-specific health psychology interventions were generally effective. Evidence is not clear-cut regarding the effectiveness of physical therapies and psychosocial interventions were generally ineffective. Interventions that investigated the effects of treatments for HIV and HIV-associated conditions on depression generally found that these treatments did not increase but often decreased depression. Interventions are both effective and available, although further research into enhancing efficacy would be valuable. Depression needs to be routinely logged in those with HIV infection during the course of their disease. Specific data on women, young people, heterosexual men, drug users and those indiverse geographic areas are needed. Measurement of depression needs to be harmonized and management into care protocols incorporated.     

Consciousness cannot be separated from function

Numerous theories of consciousness hold that there are separate neural correlates of conscious experience and cognitive function, aligning with the assumption that there are 'hard' and 'easy' problems of consciousness. Here, we argue that any neurobiological theory based on an experience/function division cannot be empirically confirmed or falsified and is thus outside the scope of science. A 'perfect experiment' illustrates this point, highlighting the unbreachable boundaries of the scientific study of consciousness. We describe a more nuanced notion of cognitive access that captures personal experience without positing the existence of inaccessible conscious states. Finally, we discuss the criteria necessary for forming and testing a falsifiable theory of consciousness.     

Trait Meta-Mood and Subjective Happiness: A 7-week Prospective Study

The primary aim of the current study was to replicate and extend previous findings by examining the relationship between trait meta-mood and levels of subjective happiness in a 7-week follow-up study. Participants were 192 undergraduate students (155 females) who completed self-report measures of trait meta-mood and subjective happiness. After 7 weeks, 155 students completed the subjective happiness scale again. Focusing first on cross-sectional analysis, meta-mood dimensions were found to be moderately related to levels of subjective happiness. Next, along with initial levels of subjective happiness, we found that meta-mood dimensions independently predicted prospective levels of subjective happiness over a 7-week follow-up. These findings provide some preliminary evidence on the prospective value of meta-mood dimensions as relevant individual differences involved in the maintenance of emotional well-being indicators.     

Chimpanzee problem-solving: contrasting the use of causal and arbitrary cues

Humans are able to benefit from a causally structured problem-solving context rather than arbitrarily structured situations. In order to better understand nonhuman causal cognition, it is therefore important to isolate crucial factors that might differentiate between events that follow a purely spatial and temporal contingency and those that hold a “true” causal relationship. In the first of two experiments, chimpanzee subjects were required to detect a bottle containing juice from five opaque bottles of equal shape and size. In the causal condition, the juice bottle looked identical to the other four bottles, only it was much heavier than the others. In the arbitrary condition, the weight of all five bottles was identical, but the juice bottle was color-marked differently. Since bottle opening was made difficult (and therefore costly), the question was whether subject’s manipulative behavior would be random or somehow influenced by the nature of the provided information. Our results show that subjects detected and opened the juice bottle significantly faster when weight was the discriminating feature (causal condition) compared to situations in which the discrimination was necessarily based on a color-cue (arbitrary condition). Experiment 2 ruled out the possibility of a general learning bias toward tactile rather than visual information in chimpanzees. When tested in a simple exchange paradigm that prevented any use of causal information, no predominance of a tactile cue (weight) over a visual cue (color) could be found. Furthermore—and in contrast to the causal condition in Experiment 1—no learning occurred during the course of Experiment 2, neither in the weight nor in the color condition. We therefore conclude that chimpanzees can more easily determine the content of an object based on its causal properties compared to situations in which the only available information is a pure arbitrary regularity. This supports the view that chimpanzees’ causal cognition does not rely on mere perceptual information but also on structural abstraction about their physical environment.