The effects of metabolic stress and vagotomy on emotional learning in an animal model of anxiety

The aim of the present study is to evaluate the role of the blood glucose (BG) level in emotional learning in the elevated plus maze (EPM), an animal model of anxiety. In Experiment 1, male Wistar rats were submitted to different EPM trial lengths (1- or 5-min). Blood samples were withdrawn before and after the maze exploration, through a polyethylene cannula chronically implanted into the jugular vein. In Experiment 2, the animals received either saline or 2-deoxy-D-glucose, a glucoprivic drug (2-DG, 250 or 500 mg kg(-1)) by i.p. route, 30 min before a 5-min EPM exposure and were retested in the maze (Trial1/Trial2 EPM procedure) 24 h later. In an independent group of rats, blood samples were withdrawn 0, 5, 15, and 30 min after 2-DG administration, through the jugular vein, to determine BG. In Experiment 3, the animals underwent a vagotomy and were tested in a Trial1/Trial2 EPM procedure four weeks later. The results showed that rats exploring the EPM for 5 min displayed increased fear and higher hyperglycemia than those exploring the EPM for 1 min. In addition, rats submitted to 5-min EPM Trial1 length displayed higher level of fear on Trial2, as well as higher percentage of shortening of the %Open arm entries and %Open arm time from Trial1 to Trial2, which characterizes the occurrence of emotional learning. In contrast, rats previously vagotomized or treated with 2-DG (500 mg kg(-1)) showed the same level of fear on both EPM trials and a low percentage of shortening, from Trial1 to Trial2, of the %Open arm entries and %Open arm time, indicating poor emotional learning. The data is discussed regarding the role of glycaemia in emotional learning in the EPM.     

Na+,K(+)-ATPase activity is reduced in hippocampus of rats submitted to an experimental model of depression: effect of chronic lithium treatment and possible involvement in learning deficits

This study was undertaken to verify the effects of chronic stress and lithium treatments on the hippocampal Na+,K(+)-ATPase activity of rats, as well as to investigate the effects of stress interruption and post-stress lithium treatment on this enzyme activity and on spatial memory. Two experiments were carried out; in the first experiment, adult male Wistar rats were divided into two groups: control and submitted to a chronic variate stress paradigm, and subdivided into treated or not with LiCl. After 40 days of treatment, rats were killed, and Na+,K(+)-ATPase activity was determined. In the second experiment, rats were stressed during 40 days, and their performance was evaluated in the Water Maze task. The stressed group was then subdivided into four groups, with continued or interrupted stress treatment and treated or not with lithium for 30 additional days. After a second evaluation of performance in the Water Maze, rats were killed and Na+,K(+)-ATPase activity was also measured. Results showed an impairment in Na+,K(+)-ATPase activity and in Water Maze performance of chronically stressed rats, which were prevented by lithium treatment and reversed by lithium treatment and by stress interruption. These results suggest that the modulation of Na+,K(+)-ATPase activity may be one of the mechanisms of action of lithium in the treatment of mood disorders.     

Television and aggression: a test of a mediated model with a sample of Portuguese students

We examined the role of identification with violent TV heroes, enjoyment of TV violence, and perceived reality in TV violence as mediators of the relationship between viewing TV violence and subsequent physical and verbal aggression. A sample of 722 4th, 6th, and 8th grade students from schools in the central region of Portugal completed measures assessing enjoyment of TV violence, perceived reality, aggression, identification with violent TV heroes, and exposure to TV violence. The results showed that the relationship between TV violence and physical aggression is mediated by enjoyment of TV violence, perceived reality in TV violence, and identification with violent TV heroes. The TV violence to verbal aggression relationship was also mediated by enjoyment of TV violence.     

Relative age effect in Olympic Taekwondo athletes

Relative age effects refer to the effects of age differences among individuals who have been grouped together for a performance activity. This study aimed to investigate the relative age effect on Olympic Taekwondo athletes, in several Olympic Games, and in both sexes. The study sample consisted of 291 athletes who had competed in Atlanta, Sydney, and Beijing Olympic Games. The relative age effect was examined for the general distribution of athletes by quartile, for each of the individuals, and for male and female athletes. There were no discernable effects of relative age on Olympic Taekwondo athletes.     

Neurofunctional (re)organization underlying narrative discourse processing in aging: evidence from fNIRS

Relatively few studies have analyzed the mechanisms underlying the cognitive changes that affect language in the elderly, and fewer have done so for narrative discourse. The goal of this study was to explore the neurofunctional changes associated with aging for different components of narrative discourse. Functional near-infrared spectroscopy (fNIRS) and behavioral data on 10 younger adults and 10 healthy elderly participants were collected. Ten younger adults in a non-proficient second language condition were included to explore the possibility that the age-related neurofunctional reorganization partly expresses demanding resource allocation. Results show within- and across-hemispheric differences in the neurofunctional pattern of activation in the older participants with reference to the younger ones, partially shared with the low-proficiency young adults, providing support for the recognized mechanisms underlying neural reserve and compensation. fNIRS was shown to be appropriate for studying the age-related neurofunctional reorganization of complex cognitive abilities.     

Towards a mathematical model of within-session operant responding

Operant response rate changes within the course of a typical free-operant experimental session. These changes are orderly, and reliably demonstrated with subjects from different species, responding under different experimental conditions. Killeen (1995) postulated that the response rate changes are a function of the interplay between arousal and satiation and offered a mathematical model for this hypothesis. Here we analyze Killeen's model, demonstrating that, although solid in its principles, it presents some flaws in its implementation. Then, based on the same principles, we build and test a new model of within-session motivation dynamics. We also demonstrate that, by representing arousal as a variable that ranges between 0 and 1, we can obtain a surprisingly simple model of free-operant response rate.     

Opioid mechanisms are involved in the disruption of arcaine-induced amnesia by context pre-exposure

Previous exposure to the training context disrupts glutamatergic N-methyl-d-aspartate receptor (NMDAr) antagonist-induced amnesia, indicating that novelty is necessary for such an amnestic effect. While there are reports that novelty-related release of opioids cause amnesia, no study has addressed whether the amnestic effect of NMDAr antagonists involve opioid mechanisms. In this study we investigated whether pharmacological manipulation of the opioid system immediately after context pre-exposure alters the amnestic effect of arcaine, a NMDAr antagonist. Adult male Wistar rats were habituated (pre-exposed) to a fear conditioning training apparatus or to a different context (open field). Immediately after pre-exposure, animals were injected with saline or naloxone (0.5 mg/kg, i.p.) or anti-beta-endorphin antibody (1:500, i.c.v.). Forty eight hours after pre-exposure session, all animals were subjected to fear conditioning acquisition protocol and saline or arcaine (30 mg/kg, i.p.) was administered immediately after training. Testing was carried out 24 h later, and freezing responses due to re-exposure to the training apparatus were recorded. Pre-exposure to the training apparatus prevented the impairment of memory induced by post-training arcaine. Administration of naloxone or anti-beta-endorphin antibody, immediately after pre-exposure to the training apparatus, reinstated the amnesic effect of post-training arcaine. The results suggest that endogenous opioid mechanisms are involved in the pre-exposure-induced loss of the amnestic effect of arcaine.     

Husserl on Geometry and Spatial Representation

Husserl left many unpublished drafts explaining (or trying to) his views on spatial representation and geometry, such as, particularly, those collected in the second part of Studien zur Arithmetik und Geometrie (Hua XXI), but no completely articulate work on the subject. In this paper, I put forward an interpretation of what those views might have been. Husserl, I claim, distinguished among different conceptions of space, the space of perception (constituted from sensorial data by intentionally motivated psychic functions), that of physical geometry (or idealized perceptual space), the space of the mathematical science of physical nature (in which science, not only raw perception has a word) and the abstract spaces of mathematics (free creations of the mathematical mind), each of them with its peculiar geometrical structure. Perceptual space is proto-Euclidean and the space of physical geometry Euclidean, but mathematical physics, Husserl allowed, may find it convenient to represent physical space with a non-Euclidean structure. Mathematical spaces, on their turn, can be endowed, he thinks, with any geometry mathematicians may find interesting. Many other related questions are addressed here, in particular those concerning the a priori or a posteriori character of the many geometric features of perceptual space (bearing in mind that there are at least two different notions of a priori in Husserl, which we may call the conceptual and the transcendental a priori). I conclude with an overview of Weyl’s ideas on the matter, since his philosophical conceptions are often traceable back to his former master, Husserl.