| Abstract: This work was part of a main project that aimed to investigate the relationship between sleep and aversive learning. To do that, we first adapted a contextual fear conditioning task in order to explore the effect of an aversive event (the electric shock) and a possible effect of forgetting controlled by the passage of time upon conditioning and extinction. The first one, the cumulative extinction group received a contextual fear conditioning (CFC) training session with a single shock presentation followed by five sessions of extinction, starting three days after CFC training. The second group, unique extinction, were trained in CFC followed by six days of no exposure to the trained context and finally an extinction session at the fifth day after training. The third group immediate shock received a training session with a single shock applied immediately after entering the animal in the conditioning box followed by five sessions of extinction. The freezing response was the behavioural parameter. The results showed that immediate shock group did not learn the conditioned relation between US-CS. The cumulative extinction group had a progressive decrease on freezing while unique extinction had a higher score on its last extinction session of the other two groups. These results are consistent with other findings and show the important role of time within a new environment to the environment to proper fulfil the requirements to acquire conditioned properties and the resistance of a conditioned relation to the passage of time. |