Brain strengthens memories during sleep
Our brain accumulates information during the day, but how is it stored in our memory? How are memories maintained over time? One of the main mechanisms is the consolidation of memory: the brain selects what we remember and what we forget.
Our brain accumulates information during the day, but how is it stored in our memory? How are memories maintained over time? One of the main mechanisms is the consolidation of memory: the brain selects what we remember and what we forget.
The optimum moment for the consolidation is during sleep via the reactivation of information. Researchers from the group of Cognition and Brain Plasticity, the Bellvitge Biomedical Research Institute (IDIBELL) and the University of Barcelona, together with the Epilepsy Unit of Bellvitge University Hospital, have proved the key role of hippocampus (a brain structure involved in memory) in the process of memory reactivation and consolidation.
To investigate, two groups of epileptic patients with selective unilateral or bilateral hippocampal sclerosis and a group of matched healthy controls were selected.
When patients were admitted before surgery, they underwent a test to see whether reactivation of information during sleep improved memory consolidation.
Researcher Lluís Fuentemilla, from the Department of Basic Psychology of the UB and coordinator of the study, explains how the test was conducted: “Before going to sleep, patients were requested to learn a series of sound-word pairs which were not semantically related, for example: applause matched the image of a table. Then, sounds that cued only half of the learned memories were presented again during the slow-wave stage at night, and in the morning a memory test was administered”.
The strengthening of reactivated memories was observed only in control subjects and epileptic patients with one preserved hippocampus, but not for patients with hippocampus which is bilaterally affected by sclerosis. “Our findings prove the critical role of the hippocampus in selective memory strengthening via reactivation”, concludes Fuentemilla.
Researchers affirm that the finding may be useful, on one hand, to further research using therapies that include memory reactivation during sleep in patients with brain injuries and, on the other hand, to open a new research line on the neuronal mechanisms which store our learning.
Pablo Ripollés, Adrià Vilà Balló and Antoni Rodríguez Fornells, from the Department of Basic Psychology, also participated in the study