Efeitos da alteração dos níveis de ansiedade no desempenho de ratos em uma tarefa de discriminação apetitiva

The plus-maze discriminative avoidance paradigm has been used to study the relationship between aversive memory and anxiety. The present study aims to verify if the elevated plus-maze can provide information about appetitive memory and anxiety, through a task motivated by food reward. Animals were allowed to explore an elevated plus-maze and received reinforcement in one of the enclosed arms. In a test session performed 24h later, in the absence of reward, rats showed preference for the previously rewarded enclosed arm over the neutral enclosed arm. The administration of diazepam and pentylenetetrazole before training induced, respectively, anxiolytic and anxiogenic effects (as evaluated by open-arm exploration). Both drugs induced amnestic effects, i.e., lack of preference for the rewarded arm in the test session. The results suggest that appetitive memory can be influenced by anxiety levels as well. The plus-maze appetitive discrimination task seems to be a useful model to investigate the relationship between memory and anxiety

Tomada de decisão individual e aprendizado em Dinoponera quadríceps (Ponerinae, Hymenoptera) forrageando em ambientes dinâmicos

When searching for food, animals often make decisions of where to go, how long to stay in a foraging area and whether or not to return to the last visited spot. These decisions can be enhanced by cognitive traits and adjusted based on previous experience. In social insects such as ants, foraging efficiency have an impact on both individual and colony level. The present study investigated, in the laboratory, the effect of distance from food, capture success and food size, and reward rate on decisions of where to forage in Dinoponera quadriceps, a ponerine ant that forage solitarily and individually make their foraging decisions. We also investigated the influence of learning on the performance of workers over successive trips searching for food by measuring the patch residence time in each foraging trip. Four scenarios were created differing in food reward rates, food size offered and distances colony-food site. Our work has shown that as a rule-of-thumb, workers of D. quadriceps return to the place where a prey item was found on the previous trip, regardless of distance, food size and reward rate. When ants did not capture preys, they were more likely to change path to search for food. However, in one of the scenarios, this decision to switch paths when unsuccessful was less evident, possibly due to the greater variation of possible outcomes ants could experience in this scenario and cognitive constraints of D. quadriceps to predict variations of food distribution. Our results also indicated a learning process of routes of exploration as well as the food site conditions for exploration. After repeated trips, foragers reduced the patch residence time in areas that they did not capture food and quickly changed of foraging area, increasing their foraging efficiency.