Retrieval and reconsolidation of object recognition memory are independent processes in the perirhinal cortex.

Reconsolidation refers to the destabilization/re-stabilization process upon memory reactivation. However, the parameters needed to induce reconsolidation remain unclear. Here we evaluated the capacity of memory retrieval to induce reconsolidation of object recognition memory in rats. To assess whether retrieval is indispensable to trigger reconsolidation, we injected muscimol in the perirhinal cortex to block retrieval, and anisomycin (ani) to impede reconsolidation. We observed that ani impaired reconsolidation in the absence of retrieval. Therefore, stored memory underwent reconsolidation even though it was not recalled. These results indicate that retrieval and reconsolidation of object recognition memory are independent processes.

[Memory-linked morphological changes]. / Cambios morfológicos asociados a la memoria.

INTRODUCTION: It has been suggested that storing information in the brain takes place by means of changes in synaptic communication efficiency, which is known as neuronal plasticity. Plastic events include changes in the function, structure, distribution and number of synapses, and it has been suggested that these plastic events could be related to learning and memory. DEVELOPMENT: In this work we will review some studies that report structural changes in which experience and learning intervene. In particular, structural changes have been observed in a region of the brain called the hippocampus, which plays a crucial role in the learning and memory of spatial tasks. It has been claimed that the appearance of new synapses after learning a spatial task is linked to the formation of long-term memory and that the functioning of NMDA-type glutamate receptors is needed for both learning and the formation of new synapses to take place. CONCLUSIONS: Understanding the cellular mechanisms involved in the formation of memory is of utmost importance to be able to check the memory deficiencies that arise from injuries or as a consequence of old age and neurodegenerative diseases.

Cambios morfológicos asociados a la memoria / Memory-linked morphological changes

Introducción. Se ha sugerido que el almacenamiento de la información en el cerebro ocurre a través de cambios en la eficiencia de la comunicación sináptica, llamada plasticidad neuronal. Los eventos plásticos incluyen cambios en la función, la estructura, la distribución y el número de sinapsis, y se ha sugerido que estos eventos plásticos pueden relacionarse con el aprendizaje y la memoria. Desarrollo. En este trabajo se revisarán algunos estudios que comunican cambios estructurales mediados por la experiencia y el aprendizaje. En particular, se han observado cambios estructurales en una región del cerebro llamada hipocampo, que es crucial para el aprendizaje y la memoria de tareas espaciales. Se ha sugerido que la aparición de nuevas sinapsis después del aprendizaje de una tarea espacial se relaciona con la formación de la memoria a largo plazo, y que para que ocurran tanto el aprendizaje como la formación de nuevas sinapsis se necesita el funcionamiento de los receptores para glutamato del tipo NMDA. Conclusión. Entender los mecanismos celulares implicados en la formación de la memoria es de suma importancia para poder revertir los déficit de memoria ocasionados por lesiones, o como consecuencia de la vejez y de enfermedades neurodegenerativas (AU)

Introduction. It has been suggested that storing information in the brain takes place by means of changes in synaptic communication efficiency, which is known as neuronal plasticity. Plastic events include changes in the function, structure, distribution and number of synapses, and it has been suggested that these plastic events could be related to learning and memory. Development. In this work we will review some studies that report structural changes in which experience and learning intervene. In particular, structural changes have been observed in a region of the brain called the hippocampus, which plays a crucial role in the learning and memory of spatial tasks. It has been claimed that the appearance of new synapses after learning a spatial task is linked to the formation of long-term memory and that the functioning of NMDA-type glutamate receptors is needed for both learning and the formation of new synapses to take place. Conclusions. Understanding the cellular mechanisms involved in the formation of memory is of utmost importance to be able to check the memory deficiencies that arise from injuries or as a consequence of old age and neurodegenerative diseases (AU)

Spatial long-term memory is related to mossy fiber synaptogenesis.

Structural synaptic changes have been suggested to underlie long-term memory formation. In this work, we investigate if hippocampal mossy fiber synaptogenesis induced by water maze overtraining can be related with long-term spatial memory performance. Rats were trained in a Morris water maze for one to five identical daily sessions and tested for memory retrieval 1 week and 1 month after training. After the last test session, the rat brains were obtained and processed for Timm's staining to analyze mossy fiber projection. The behavioral results showed that with more training, animals showed a better performance in the memory tests, and this performance positively correlates with Timm's staining in the stratum oriens. Furthermore, with the use of the NMDA antagonist MK801 before, but not after acquisition, water maze spatial memory was impaired. Increased Timm's staining in the stratum oriens was observed in the animals treated with MK801 after acquisition but not in those treated before. Finally, we observed that mossy fiber synaptogenesis occurs mainly in the septal region of the dorsal hippocampus, supporting the idea that this anterior region is important for spatial memory. Altogether, these results suggest that mossy fiber synaptogenesis can be related with spatial long-term memory formation.