An inhibitory within-compound association attenuates overshadowing

According to the comparator hypothesis (Miller & Matzel, 1988), cue competition depends on the association between a target stimulus (X) and a competing cue (e.g., an overshadowing cue [A]). Thus, it was expected that overshadowing would be reduced by establishing an inhibitory-like relationship between X and A before compound conditioning. In three lever press suppression experiments with rats, this expectation was supported. Experiment 1 showed that establishing an inhibitory X-A relationship reduced overshadowing. In Experiment 2, degrading the inhibitory-like relationship before conditioning allowed reinforced AX compound trials to result in overshadowing. Experiment 3 replicated the results of Experiment 2 when the inhibitory relationship was degraded after compound conditioning. The results support the view that within-compound associations are necessary not only for retrospective revaluation, but also for conventional cue competition.     

Group communication and decision-making strategies

In daily life, people frequently make inferences about current and future states of the world. Most of these inferences are not made individually, but by exchanging information about which strategies could be used with other people. In an experiment, we analyzed whether exchanging information socially increased the probability of selecting the most adaptive strategy. In our experiment, take-the-best (TTB; Gigerenzer & Goldstein, 1996), a simple heuristic that employs one-reason decision making, achieved the highest payoff. Results showed that the fit of TTB increased substantially across trial blocks when participants were allowed to exchange information with other group members. In contrast, when participants made inferences individually, they did not select the most adaptive strategy even after seven trial blocks. Overall, our results support the hypothesis that group communication increases the likelihood that participants select the most adaptive strategy for making inferences.     

Cognitive plasticity in Alzheimer's disease patients receiving cognitive stimulation programs

The main purpose of this article is to examine whether cognitive plasticity increases after cognitive training in Alzheimer's disease patients. Twenty six patients participated in this study, all of them diagnosed with mild Alzheimer's disease, 17 of them received a cognitive training program during 6 months, and the other 9 were assigned to the control group. Participants were assigned to experimental or control conditions for clinical reasons. In order to assess cognitive plasticity, all patients were assessed before and after treatment with three subtests from the "Bateria de Evaluación de Potencial de Aprendizaje en Demencias" [Assessment Battery of Learning Potential in Dementia] (BEPAD). After treatment, Alzheimer's disease patients improved their performance in all the tasks assessing cognitive plasticity: viso-spatial memory, audio-verbal memory and verbal fluency. However, the cognitive plasticity scores of the patients in the control group decreased. In conclusion, this study showed that cognitive stimulation programs can improve cognitive functioning in mildly demented patients, and patients who do not receive any cognitive interventions may reduce their cognitive functioning.     

Execution and pauses in writing narratives: processing time, cognitive effort and typing skill

At the behavioural level, the activity of a writer can be described as periods of typing separated by pauses. Although some studies have been concerned with the functions of pauses, few have investigated motor execution periods. Precise estimates of the distribution of writing processes, and their cognitive demands, across periods of typing and pauses are lacking. Furthermore, it is uncertain how typing skill affects these aspects of writing. We addressed these issues, selecting writers of low and high typing skill who performed dictation and composition tasks. The occurrences of writing processes were assessed through directed verbalization, and their cognitive demands were measured through interference in reaction times (IRT). Before writing a narrative, 34 undergraduates learned to categorize examples of introspective thoughts as different types of activities related to writing (planning, translating, or revising). Then, while writing, they responded to random auditory probes, and reported their ongoing activity according to the learned categories. Convergent with previous findings, translating was most often reported, and revising and planning had fewer occurrences. Translating was mostly activated during motor execution, whereas revising and planning were mainly activated during pauses. However, none of the writing processes can be characterized as being typical of pauses, since translating was activated to a similar extent as the other two processes. Regarding cognitive demands, revising is likely to be the most demanding process in narrative writing. Typing skill had an impact on IRTs of motor execution. The demands of execution were greater in the low than in the high typing skill group, but these greater demands did not affect the strategy of writing processes activation. Nevertheless, low typing skill had a detrimental impact on text quality.     

Gabaergic mechanisms of hypothalamic nuclei in the expression of conditioned fear

The amygdala, the dorsal periaqueductal gray (dPAG), and the medial hypothalamus have long been recognized to be a neural system responsible for the generation and elaboration of unconditioned fear in the brain. It is also well known that this neural substrate is under a tonic inhibitory control exerted by GABA mechanisms. However, whereas there is a growing body of evidence to suggest that the amygdala and dPAG are also able to integrate conditioned fear, it is still unclear, however, how the distinct hypothalamic nuclei participate in fear conditioning. In this work we aimed to examine the extent to which the gabaergic mechanisms of this brain region are involved in conditioned fear using the fear-potentiated startle (FPS). Muscimol, a GABA-A receptor agonist, and semicarbazide, an inhibitor of the GABA synthesizing enzyme glutamic acid decarboxylase (GAD), were used as an enhancer and inhibitor of the GABA mechanisms, respectively. Muscimol and semicarbazide were injected into the anterior hypothalamus (AHN), the dorsomedial part of the ventromedial nucleus (VMHDM), the dorsomedial (DMH) or the dorsal premammillary (PMD) nuclei of male Wistar rats before test sessions of the fear conditioning paradigm. The injections into the DMH and PMD did not produce any significant effects on FPS. On the other hand, muscimol injections into the AHN and VMHDM caused significant reduction in FPS. These results indicate that injections of muscimol and semicarbazide into the DMH and PMD fail to change the FPS, whereas the enhancement of the GABA transmission in the AHN and VMHDM produces a reduction of the conditioned fear responses. On the other hand, the inhibition of this transmission led to an increase of this conditioned response in the AHN. Thus, whereas DMH and PMD are known to be part of the caudal-most region of the medial hypothalamic defensive system, which integrates unconditioned fear, systems mediating conditioned fear select the AHN and VMHDM nuclei that belong to the rostral-most portion of the hypothalamic defense area. Thus, distinct subsets of neurons in the hypothalamus could mediate different aspects of the defensive responses.     

Age-related Changes in Postural Sway During Sit-to-stand in Typical Children and Children with Cerebral Palsy

Objective: To assess age-related changes in postural sway during sit-to-stand (STS) in typical children (TC) and children with mild cerebral palsy (CP). Methods: Thirty-five TC and 23 children with mild CP were allocated in four different age groups: 5–6, 7–9, 10–12, and 13–15 years; they all performed STS movements over a force plate. Anterior-posterior and medial-lateral amplitude of center of pressure (CoP) displacement, area and velocity of CoP sway were analyzed and compared between the age groups for TC and children with CP. Results: TC at 5 to 6 years of age showed higher values of anterior-posterior CoP displacement and Area of CoP sway than at 10–12 years, during the stabilization phase. There were no age-related changes for CP. Conclusion: TC change their postural sway during the last STS phase over the years, reducing their body sway. Children with CP did not show age-related changes in sway during STS, reflecting a distinct rhythm of postural control development in this population.     

Cathodal tDCS of the Left Posterior Parietal Cortex Increases Proprioceptive Drift

In aiming movements the limb position drifts away from the defined target after some trials without visual feedback, a phenomenon defined as proprioceptive drift (PD). There are no studies investigating the association between the posterior parietal cortex (PPC) and PD in aiming movements. Therefore, cathodal and sham transcranial direct current stimulation (tDCS) were applied to the left PPC concomitantly with the performance of movements with or without vision. Cathodal tDCS applied without vision produced a higher level of PD and higher rates of drift accumulation while it decreased peak velocity and maintained the number of error corrections, not affecting movement amplitude. The proprioceptive information seems to produce an effective reference to movement, but with PPC stimulation it causes a negative impact on position.     

The Short Dark Triad (SD3): Adaptation and Psychometrics among At-Risk Male and Female Youths

The dark triad is a term used to describe a constellation of three socially harmful personality traits: Machiavellianism, psychopathy, and narcissism. The main aim of the present study was to examine the psychometric properties of the Short Dark Triad (SD3) scale, a brief measure of the dark triad, among a sample (N = 412) of male (n = 200) and female (n = 212) at-risk Portuguese youths. Confirmatory factor analysis revealed the three-factor structure of the SD3 obtained an adequate fit, and measurement invariance across gender was demonstrated, although two items per dimension had to be removed. The Portuguese version of the SD3 scale demonstrated satisfactory psychometric properties, specifically the properties of internal consistency, convergent validity, discriminant validity, and known-groups validity, which overall justifies its use among this population. Findings are discussed in terms of the use of the SD3 scale with male and female at-risk youths.