A research by the University of Oviedo sheds new light on the recovery of memory in cases of brain injury. The Research Group of Behavioral Neuroscience has demonstrated in experimental models that when there is a unilateral injury to the hippocampus, linked to memory loss, the brain maintains a network of connections with the affected structures. As a consequence, with the proper stimulation, memory could be restored. This work, which will be published in the prestigious free-access scientific journal PLOS ONE, is an advance in the study and treatment of amnesia related to spatial orientation, or in other words, being unable to recall certain places, such as the location of our house.

The Group of Behavioral Neuroscience, incorporated into the recently consolidated Institute of Neuroscience of the Principality of Asturias (INEUROPA), has been researching for more than 20 years the biological bases of learning and memory processes related to the ability for spatial orientation. A deep knowledge of the processes of adquisition, consolidation, recalling and extinction of spatial memory is absolutely necessary to understand how it is possible to evoke the memories of certain places visited long ago, or what are the neural processes involved in the common or pathological (amnesia) loss of memory, as in the case of dementia.

Since the last years of the past century, the hippocampal formation (a structure located inside the temporal medial lobe of both hemispheres of the brain in human beings) is at the forefront of the research on the biological bases of learning and memory, especially for its role in the adquisition of new memories about events that had been experienced previously. This way, injuries to the hippocampus and adjacent regions are associated, both in human beings and in experimental models, to a specific amnesia characterized by the inability to recall the position of certain relevante geographical places, such as the location of our home, or how to correctly locate it.

The research, which will be published by the scientific journal PLOS ONE, claims that, in case of an injury, the brain will maintain a network of connections, which will open the door to the recovery of memories

In this sense, there is a famous case of a patient known for their initials H. M., who underwent a surgical procedure to improve their epileptic crises. The surgey bilaterally removed their hippocampus and adjacent tissues, which caused them a a profound amnesia characterized by the inability to create new memories. Nevertheless, the effects of unilateral damage to the hippocampus are more controversial and less obvious. The research conducted by professors Nélida M. Conejo and José M. Cimadevilla (University of Almería) determined the effection of the functional bilateral or unilateral inactivity in rats, through the application of a neurotoxin that temporarily its function, about the ability to recall a long-term memory test. With their study, they prove that "memory loss is less in subjects with unilateral damage to the hippocampus, since new brain circuits are activated and facilitate recalling in the memory test", the researchers claim.

Este nuevo trabajo, en el que también participan otros investigadores del grupo NEUROCON confirma otros resultados del propio grupo investigador, que indican la existencia de diferentes redes funcionales de estructuras ampliamente distribuidas en el cerebro y que se modifican temporalmente en relación con los diferentes procesos de la memoria espacial. "El estudio tiene importantes repercusiones para la comprensión de los mecanismos biológicos compensatorios implicados en la recuperación funcional de la memoria tras el daño cerebral", añaden los autores de la investigación. This new study, in which other scientists from the NEUROCON group participate, confirms the results of the research group, poiting at the existence of different functional networks of structures widely spread in the brain that are temporarily modified according to the different processes of the spatial memory. "The study has important consequences for the understanding of the biological compensatory mechanisms involved in the functional memory recovery after a brain injury", the authors of the research state.

References:

Conejo, N.M., Cimadevilla, J.M., González-Pardo, H., Méndez-Couz, M. y Arias, J.L. (2013). Hippocampal inactivation with TTX impairs long-term spatial memory retrieval and modifies brain metabolic activity. PLOS ONE (doi: 10.1371/journal.pone.0064749).

Cimadevilla, J.M., Méndez-López, M., Méndez, M., Arias, J.L. (2011). Interhippocampal transfer in passive avoidance task modifies metabolic activity in limbic structures. Hippocampus, 21(1):48-55.

Conejo, N.M., González-Pardo, H., Gonzalez-Lima, F. y Arias, J.L. (2010). Spatial learning of the water maze: progression of brain circuits mapped with cytochrome oxidase histochemistry. Neurobiology of Learning and Memory, 93(3):362-71.