Rats were trained on an inhibitory avoidance task to study the effects of post-training administration of tetrodotoxin (TTX, which temporarily inactivates neural activity) on memory consolidation. During training, independent groups of rats received either a mild foot shock (0.8 mA) or a stronger (1.0 mA) foot shock. TTX was administered bilaterally into the dorsal hippocampus immediately after training, and memory of the task was measured 48 h later. We corroborated the typical amnesic effect of intrahippocampal infusions of TTX in those rats trained with the mild-intensity foot shock. More importantly, with the stronger foot shock, the same treatment was ineffective in producing amnesia. These results suggest that, after an enhanced learning experience, other brain regions are also activated, which may compensate for the amnesic effect of TTX infusions into the hippocampus.

Performance decrements of inhibitory avoidance (IA) induced by lesions in either the dorsal or ventral hippocampus have been interpreted as a deficiency in acquisition. Alternative interpretations are that short-term learning occurs despite the lesions and the long-term performance decrements reflect a failure of consolidation or retrieval. To assess the alternative explanations of the performance decrements, rats received lesions in either CA1 or CA3 fields of dorsal and ventral hippocampus, respectively, 8 days before IA training. Retention was tested at 30 min or 24 h after training. Kainic acid lesions were also produced in either hippocampal field 1 day after training and retention measured 8 days later. The group assessed 30 min after IA training showed little or no performance decrements, whereas the remaining groups did show marked performance decrements. These results do not support the conclusion that the hippocampus is essential for acquisition and support the idea that the hippocampus is highly involved in the consolidation or retrieval of information germane to these procedures.

No abstract

tivamente bajos de reforzamiento o de número de ensayos o de sesiones de entrenamiento, así como los derivados de situaciones de aprendizaje incrementado pueden se explicados en forma sencilla por dos modelos que hemos propuesto: la del procesamiento en serie y la del procesamiento en paralelo, que se discuten en el texto.Palabras clave: aprendizaje, memoria, amnesia, sistema nervioso, procesamiento en serie, procesamiento en paralelo, sobre-entrenamiento, sobrereforzamiento.