The role of the amygdala on trace fear conditioning

Tese de mestrado, Biologia (Biologia Evolutiva e do Desenvolvimento), 2009, Universidade de Lisboa, Faculdade de CiênciasResumo alargado disponível em portuguêsPavlovian fear conditioning is one of the most used behavioral paradigms to study the neural mechanisms of learning and memory, because fear learning is fast and long lasting. This is a type of associative learning in which a neutral stimulus, such as a tone (conditioned stimulus CS) becomes associated with an aversive one, such as a foot shock (unconditioned stimulus -US). After the association, the CS comes to elicit species specific fear responses when presented alone. Much of the work done in this area uses a protocol in which the tone and the shock overlap in time, co-terminating. The amygdala, a neural structure in the temporal lobe, is often considered crucial for this type of learning. Because it has never been properly demonstrated that this structure plays a similar role when both stimuli are separated in time, a trace fear conditioning protocol, where the presentation of the tone precedes shock delivery by several seconds, is going to be used to try to answer this question. The rat Rattus norvegicus is going to be used as a model to compare levels of freezing to the tone CS, between animals with intact amygdala and animals with reversible muscimol inactivation of the structure before training. Although the data was not sufficient to allow for statistical analysis, our data strongly suggests that activity in the amygdala is indeed necessary for fear conditioning with both short and long trace interval