Acute restraint stress and corticosterone transiently disrupts novelty preference in an object recognition task.

The object recognition task is a procedure based on rodents' natural tendency to explore novel objects which is frequently used for memory testing. However, in some instances novelty preference is replaced by familiarity preference, raising questions regarding the validity of novelty preference as a pure recognition memory index. Acute stress- and corticosterone administration-induced novel object preference disruption has been frequently interpreted as memory impairment; however, it is still not clear whether such effect can be actually attributed to either mnemonic disruption or altered novelty seeking. Seventy-five adult male Wistar rats were trained in an object recognition task and subjected to either acute stress or corticosterone administration to evaluate the effect of stress or corticosterone on an object recognition task. Acute stress was induced by restraining movement for 1 or 4h, ending 30 min before the sample trial. Corticosterone was injected intraperitoneally 10 min before the test trial which was performed either 1 or 24h after the sample trial. Four-hour, but not 1-h, stress induced familiar object preference during the test trial performed 1h after the sample trial; however, acute stress had no effects on the test when performed 24h after sample trial. Systemic administration of corticosterone before the test trial performed either 1 or 24h after the sample trial also resulted in familiar object preference. However, neither acute stress nor corticosterone induced changes in locomotor behaviour. Taken together, such results suggested that acute stress probably does not induce memory retrieval impairment but, instead, induces an emotional arousing state which motivates novelty avoidance.

Evaluación del efecto de bloqueo en el condicionamiento clásico de preferencias / Assessment of the blocking effect in classical conditioning of preferences

Esta investigación experimental tuvo como objetivo poner a prueba el efecto de bloqueo de Kamin en el condicionamiento clásico de preferencias. Se diseñaron tres partes: Estudio 1, Experimento 1 y Experimento 2. El Estudio preliminar (n = 54) consistió en la elección de los estímulos condicionados (marcas publicitarias ficticias) y del estímulo incondicionado (figura femenina con una proporción controlada de la medida de cintura/ cadera). En el Experimento 1 (n = 60) se efectuó el entrenamiento en condicionamiento clásico de preferencias. Finalmente, en el Experimento 2 (n = 40), se examinó el efecto de bloqueo en el condicionamiento clásico de preferencias con pruebas de tipo cognoscitivo y afectivo. Participaron estudiantes universitarios de diferentes carreras entre 17 y 25 años. Los resultados indican que se manifestó un efecto de bloqueo en tres de las cuatro pruebas utilizadas para evaluar dicho fenómeno. Se plantea, a manera de conclusión, que este efecto potencialmente explica diferentes fenómenos en los campos de la publicidad y el mercadeo, especialmente en lo que concierne a competencia de marcas.

This experimental research was aimed to test Kamin's blocking effect in classical conditioning of preferences applied in the advertisement area. This study was divided into three parts: preliminary Study, Experiment 1, and Experiment 2. In the preliminary Study, both conditioned (a false publicity brand) and unconditioned stimuli (female figure with a controlled waist-to-hip ratio) were selected. Experiments 1 and 2 consisted of training in classical conditioning of preferences and blocking effect. 17-25 year-old undergraduate students of different careers participated in the present study. According to the results, a blocking effect was observed, suggesting an explanation for different phenomena in fields such as marketing or advertisement, especially when implying brands competition.