Resumen de Efeitos de histórias recente e remota sobre o desempenho em esquemas de intervalo fixo

Carlos Eduardo Costa, Carla Jordão Suarez, Carlos Renato Xavier Cançado, Rodrigo Morande Becker

• English

  The results of previous experiments conducted with humans have suggested that, after a history of exposure to a DRL schedule, response rates under an FI schedule tend to be low. These effects have been observed with humans regardless if the history of exposure to the DRL schedule is preceded or succeeded by a history of exposure to an FR schedule which generates high response rates (i.e., whether exposure to the DRL schedule is part of the individual’s recent or remote history). These consistent effects of a recent or remote DRL history on FI-schedule performance, however, have not been observed in experiments with rats. Thus, the goal of the present experiment was to assess, with rats, if the stimulus in effect in each experimental phase would modulate history effects on FI-schedule performance. During the experiment, rats were maintained at 85% of their free-feeding weights and were distributed in seven groups (n=3). The rats in Group 1 were exposed only to an FI schedule; the rats in groups 2, 4 and 5 were exposed to an FR and to a DRL schedule in the Remote History and Recent History phases, respectively; the rats in groups 3, 6 and 7 were exposed to a DRL and to an FR schedule in the Remote History and Recent History phases, respectively. The Remote and Recent History phases were conducted for a minimum of six sessions and until the difference between the mean response rates of the first three and last three sessions of a block of the last six sessions was lower than 15% of the mean response rate of the last six sessions. In the Test phase, rats in each group were exposed to an FI schedule for 15 sessions. In addition, for the rats in groups 4, 5, 6 and 7, the stimulus in effect in each phase was manipulated. That is, for these rats, the houselight was on during sessions in the Remote History phase and off during sessions in the Recent History phase. During sessions in the Test phase, the houselight was on, for the rats in groups 4 and 6, and off, for those in groups 5 and 7. Recent history effects (of FR or DRL schedules) on FI-schedule performance were observed consistently, regardless if the stimulus in effect in the Test phase was similar to that in effect in the Remote History or Recent History phases. The present results replicate those of previous studies with rats, but fail to replicate some results obtained with humans exposed to similar procedures.

  That is, when rats have been exposed to different schedules of reinforcement sequentially, rather than simultaneously, in the history phases, recent history effects have been observed consistently under FI schedules. The role of stimuli in modulating history effects is discussed in the context of sequential vs. simultaneous exposure to the different schedules of reinforcement in the Remote and Recent History phases.

• português

  Avaliaram-se os efeitos de histórias recente e remota sobre o desempenho atual de ratos em esquemas FI, sob a mesma ou diferentes condições de estímulos. Os ratos foram distribuídos em sete grupos: os do Grupo 1 foram expostos apenas a um FI; os dos grupos 2, 4 e 5, foram expostos a um FR e a um DRL nas fases de História Remota e História Recente, respectivamente; os ratos dos grupos 3, 6 e 7 foram expostos a um DRL e a um FR nas fases de História Remota e História Recente, respectivamente. Na Fase de Teste, todos os ratos foram expostos a um FI. Para os ratos dos grupos 4 a 7, manipulou-se o estímulo em vigor em cada fase. Para esses ratos, nas fases de História Remota e História Recente, a luz da câmara estava acesa e apagada, respectivamente.

  Na Fase de Teste, a luz estava acesa, para os ratos dos grupos 4 e 6, e apagada, para os ratos dos grupos 5 e 7. Efeitos de histórias recentes (FR ou DRL) foram observados sobre o comportamento em FI, independentemente de os estímulos na fase de Teste terem sido semelhantes àqueles em vigor na fase de História Remota ou História Recente.