The effect of sample duration and cue on a double temporal discrimination

To test the assumptions of two models of timing, Scalar Expectancy Theory (SET) and Learning to Time (LeT), nine pigeons were exposed to two temporal discriminations, each signaled by a different cue. On half of the trials, pigeons learned to choose a red key after a 1.5-s horizontal bar and a green key after a 6-s horizontal bar; on the other half of the trials, they learned to choose a blue key after a 6-s vertical bar and a yellow key after a 24-s vertical bar. During subsequent test trials, they were exposed to the horizontal or vertical bar, for durations ranging from 1.5 to 24 s, and given a choice between novel key combinations: red vs. yellow, or green vs. blue. Results showed a strong effect of sample duration—as the test signal duration increased, preference for green over blue increased and preference for red over yellow decreased. The effect of sample cue was obtained only on the green-blue test trials. These effects are discussed in light of SET and LeT.     

ENSEMBLE RECORDINGS IN AWAKE RATS: ACHIEVING BEHAVIORAL REGULARITY DURING MULTIMODAL STIMULUS PROCESSING AND DISCRIMINATIVE LEARNING

To meet an increasing need to examine the neurophysiological underpinnings of behavior in rats, we developed a behavioral system for studying sensory processing, attention and discrimination learning in rats while recording firing patterns of neurons in one or more brain areas of interest. Because neuronal activity is sensitive to variations in behavior which may confound the identification of neural correlates, a specific aim of the study was to allow rats to sample sensory stimuli under conditions of strong behavioral regularity. Our behavioral system allows multimodal stimulus presentation and is coupled to modules for delivering reinforcement, simultaneous monitoring of behavior and recording of ensembles of well isolated single neurons. Using training protocols for simple and compound discrimination, we validated the behavioral system with a group of 4 rats. Within these tasks, a majority of medial prefrontal neurons showed significant firing‐rate changes correlated to one or more trial events that could not be explained from significant variation in head position. Thus, ensemble recordings can be combined with discriminative learning tasks under conditions of strong behavioral regularity.     

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.     

Transgenic mice expressing a truncated form of CREB-binding protein (CBP) exhibit deficits in hippocampal synaptic plasticity and memory storage

Deletions, translocations, or point mutations in the CREB-binding protein (CBP) gene have been associated with Rubinstein-Taybi Syndrome; a human developmental disorder characterized by retarded growth and reduced mental function. To examine the role of CBP in memory, transgenic mice were generated in which the CaMKII alpha promoter drives expression of an inhibitory truncated CBP protein in forebrain neurons. Examination of hippocampal long-term potentiation (LTP), a form of synaptic plasticity thought to underlie memory storage, revealed significantly reduced late-phase LTP induced by dopamine-regulated potentiation in hippocampal slices from CBP transgenic mice. However, four-train induced late-phase LTP is normal. Behaviorally, CBP transgenic mice exhibited memory deficits in spatial learning in the Morris water maze and deficits in long-term memory for contextual fear conditioning, two hippocampus-dependent tasks. Together, these results demonstrate that CBP is involved in specific forms of hippocampal synaptic plasticity and hippocampus-dependent long-term memory formation.     

Amnestic effect of intrahippocampal AM251, a CB1-selective blocker, in the inhibitory avoidance, but not in the open field habituation task, in rats

CB1 is the most abundant metabotropic receptor of the brain, being found in areas classically involved in learning and memory and present at higher density at presynaptic terminals. Different sets of evidence support the idea that endogenous ligands (endocannabinoids) to the CB1 receptors act as modulators of neurotransmission. In hippocampus, endocannabinoids seem to act as retrograde messengers mediating down-regulation of GABA release. Previous reports have described a cognitive impairment effect of cannabinoid agonists, or facilitation by antagonists. The scope of the present study is to investigate the effect of intrahippocampal administration of the CB1-selective antagonist, AM251, in two behavioral tasks. One hundred and twelve male Wistar rats with bilateral cannulae implanted in the CA1 region of the dorsal hippocampus were trained in a step-down inhibitory avoidance task (IA, footshock, 0.5 mA) or an open field habituation task (OF). Immediately, after training, animals received an infusion of 0.55, 5.5, and 55.5 ng/side of AM251 (Tocris), or its vehicle (DMSO/saline), via these cannulae. Our results show that AM251 disrupted memory consolidation of the IA task, but not the OF task, an effect that seems to be purely mnemonic since the drug showed no motor performance effects. Only the intermediate dose (5.5 ng/side) of AM251 was effective in IA and the absence of effect with the larger dose may be the consequence of non-specific binding. The fact that OF was not affected raises the possibility that this endogenous system requires some degree of aversiveness to be recruited. We propose that increased levels of endogenous cannabinoids in the hippocampus, following a training session, contribute to facilitate memory consolidation, a process that may have been disrupted with AM251.     

Who gets mad,sad, scared or happy at discipline? Emotion attributions explain child externalizing behaviour

Few studies have linked parental discipline with children's emotional experiences, and not much data explore children's emotional attributions to discipline linked to externalizing behaviour. With a sample from Brazil, this study examines which emotions children most aptly attribute to a protagonist facing spanking, time-out or inductive discipline for norm violations. We hypothesized that anger, sadness, and fear would have higher attribution rates at spanking or time-out, relative to inductive discipline and that happiness would have higher attribution rates at induction relative to the other discipline modalities. We expected these findings to be more pronounced in older children. Based on emotional functions, we also tested the role of neutrality and happiness attributions to discipline in children's externalizing behaviour. A two-way MANOVA, with discipline and child age as explanatory variables, showed that children attributed more anger at time-out or spanking than at induction, and more happiness and neutrality at induction than at either time-out or spanking. Older children attributed significantly more sadness and less fear or neutrality. Hierarchical regressions showed that child externalizing behaviour was negatively related to happy attributions in discipline independently of child emotion situation knowledge or demographics. The results are interpreted in light of a functional view of emotions.     

Effects of game location, period, and quality of opposition in elite handball performances

The aims of the present study were to identify (i) home advantage in elite handball according to the quality of opponent, (ii) the game periods where the teams score more goals, and (iii) the game statistics associated with the teams' success according to the game's location. The sample comprised 480 regular season games (2007-2009) from the Spanish Professional Handball League. The goals scored and shot effectiveness (6 m, 7 m, 9 m and fast breaks) were analyzed for each 5-min. game period in games between players of balanced and unbalanced quality. The home advantage was 64%, with higher values (71%) in balanced and lower values (55%) in unbalanced games. The 5-min. game periods in which teams scored more goals were the last 5-min. period of each half, especially in the second half. The effectiveness was only different in shots closer to the goal (6 m), which supports the territoriality theory of home advantage.     

Power and Legitimizing Ideologies in Hierarchy‐Enhancing vs. Hierarchy‐Attenuating Environments

According to social dominance theory, intergroup dynamics are strongly influenced by the social positions which individuals hold in society. Several studies suggest that holding a position of power can, sometimes automatically, generate negative attitudes and hostile behaviors toward subordinate social groups. However, at present, the studies carried out on these effects of power have not taken into account the influence of the normative context. Based on the distinction made by Sidanius and Pratto between “hierarchy‐enhancing” (HE) vs. “hierarchy‐attenuating” (HA) environments, this study examines if the effects of power on legitimizing cognitions vary as a function of the normative environment. A laboratory study and a study conducted in a natural environment confirm our hypothesis that individuals holding a powerful or dominant social role in a HE setting differ significantly from individuals holding an equally powerful role in a HA setting. The effects of power observed in past research probably resulted from studying power in hierarchy‐enhancing environments, but not in hierarchy‐attenuating ones.