Corticosterone and propranolol's role on taste recognition memory.

Taste recognition is a robust procedure to study learning and memory processes, as well as the different stages involved in them, i.e. encoding, storage and recall. Considerable evidence indicates that adrenal hormones and the noradrenergic system play an important role in aversive and appetitive memory formation in rats and humans. The present experiments were designed to characterize the effects of immediate post training corticosterone (Experiment 1) and propranolol administration (Experiment 2 and 3) on taste recognition memory. Administration of a high dose of corticosterone (5mg/kg, sc) impairs consolidation of taste memory, but the low and moderate doses (1 and 3mg/kg, sc) didn't affect it. On the other hand, immediate post-training administration of propranolol (1 and 2mg/kg, ip) impaired taste recognition memory. These effects were time-dependent since no effects were seen when drug administration was delayed 3h after training. These findings support the importance of stress hormones and noradrenergic system on the modulation of taste memory consolidation.

Incentive relativity in middle aged rats.

Response to a reinforcer is affected by prior experience with different reward values of that reward, a phenomenon known as incentive relativity. Two different procedures to study this phenomenon are the incentive downshift (ID) and the consummatory anticipatory negative contrast (cANC), the former is an emotional-cognitive protocol and the latter cognitive one. Aged rodents, as also well described in aged humans, exhibit alterations in cognitive functions. The main goal of this work was to evaluate the effect of age in the incentive' assessment using these two procedures. The results indicated that aged rats had an adequate assessment of the rewards but their performance is not completely comparable to that of young subjects. They recover faster from the ID and they had a cognitive impairment in the cANC. The results are discussed in relation to age-related changes in memory and emotion.

The effect of partial reinforcement on instrumental successive negative contrast in inbred Roman High- (RHA-I) and Low- (RLA-I) Avoidance rats.

Frustration is an emotional response that can be induced by the sudden devaluation of a reinforcer in the presence of greater reinforcement expectancies (e.g. instrumental successive negative contrast, iSNC). This emotional response seems to be similar to anxiety and can be attenuated by previous experiences of reward loss (e.g. partial reinforcement, PR, as opposed to continuous reinforcement, CR). In this study we used iSNC and PR procedures in order to compare the performance of two strains of rats psychogenetically selected on the basis of their emotional reactivity: the inbred Roman High- (RHA-I, low anxiety) and Low- (RLA-I, high anxiety) Avoidance rats. Animals were exposed to a straight alley, where they were changed from 12 pellets in the preshift phase (presented in 100% of trials-CR vs. 50% of trials-PR) to 2 pellets in the postshift phase, or exposed to 2 pellets throughout the training. The results indicated that the iSNC only appeared in RLA-I rats exposed to CR, as opposed to RLA-I animals exposed to PR and to RHA-I rats exposed to PR or CR. These data seem to support the implication of emotional responses in both iSNC and PR situations, and indicate that the behavioral reactivity to reward loss experiences is modulated by genetic variables.

Respuestas de frustración en humanos / Frustration response in humans

La frustración es un estado emocional que se desencadena ante acontecimientos que involucran la reducción o supresión inesperada de reforzadores apetitivos. En este artículo se presentan una serie de trabajos realizados con humanos en los cuales se omiten, devalúan o interrumpen refuerzos alimenticios, monetarios, sociales y juegos de entretenimientos. La mayoría de los resultados experimentales son análogos a los hallados con animales no humanos, aunque agregan información sobre reacciones específicamente humanas, tales como los informes verbales, las expresiones faciales y cómo se regula mediante los estilos atribucionales y la personalidad. Finalmente se discute si la frustración puede o no enmarcarse dentro de las emociones básicas.

Frustration is an emotional state elicitated by the unexpected reduction or suppression of appetitive reinforcers. In this article studies of frustration with humans are presented, in which food, monetary, social reinforcers and entertainment games are either omitted, devaluated or interrupted. The majority of the experimental results are analogous to the results founded with non-human subjects, though they add information about human reactions such as verbal reports, facial expressions, and how these responses are regulated by the contribution of attribution styles and personality. Finally, the possibility of categorizing frustration as one of the basic emotions is also discussed.

Spatial learning in South American opossums and armadillos.

This experiment compares spatial learning in the South American opossum (Didelphis albiventris) and armadillo (Chaetophractus villosus) in a Y-maze. Ss learned to turn to one arm of the maze for food reinforcement. To earn further reinforcements, they had to return to the start-box (after consuming the food) where they were restrained for a fixed intertrial interval. The number of entries to the unbaited arm en route to the goal-box (Ri errors), and in the way back to the start-box (Rf errors) were the dependent measures. Opossums and armadillos did not differ in Ri errors. However, only armadillos mastered the task of returning directly to the start-box after each reinforcement. Moreover, a significant within-session improvement in Rf errors was observed in armadillos, but failed to appear in opossums. Results are discussed in terms of species differences in sensitivity to temporal delays.