A study by the Faculty of Psychology at the Universitat de Barcelona (UB), the Institute of Neurosciences at UB (UBneuro), and the Biomedical Research Institute of Bellvitge (Idibell) has identified for the first time in humans –and in a realistic environment– the brain waves of the ‘ripple’ type, a neurophysiological mechanism that is «key» in memory formation.
These are high-frequency electrical oscillations that act as markers delimiting and organizing the different episodes or fragments of information that the brain needs to remember in the future, as reported by UB in a statement on Wednesday.
The discovery, published in the journal ‘Nature Communications’, delves into the understanding of how memory is organized in the human brain and opens up «new avenues» to address disorders related to memory deterioration.
FLOW SEGMENTATION
The recall of specific episodes is the foundation of memory, and despite the constant experience, there is «a lot of evidence» that the brain segments it when there are changes in the flow of information to turn it into memories.
The researcher from the Cognition and Brain Plasticity Group at Idibell and UBneuro and leader of the study, Lluís Fuentemilla, points out that these segments mark that, from a certain moment, the brain closes one episode in memory and starts recording another.
Previous studies in mice had indicated that ‘ripple’ waves play a «fundamental» role in memory formation: they are considered to coordinate the transfer of information between the hippocampus and neocortical regions, thus facilitating the integration of new memories.
This neuronal signal is «key» to generate synaptic potentiation, allowing the brain to fix and consolidate a memory.
EXPERIMENT
Although the signals had been widely studied in animals, their analysis in humans has been very limited due to the difficulty of recording them, as they originate in brain areas that require the use of intracranial electrodes.
In this study, researchers have managed to analyze the waves in a context close to everyday life, recording the intracranial electrophysiological activity of ten epilepsy patients –operated on for clinical reasons– while watching the first episode of ‘Sherlock’ from the BBC, a 50-minute show.
The results show a dynamic pattern of activation of ‘ripple’ waves during memory encoding, occurring in both the hippocampus and neocortical areas, although they followed a differentiated timeline.
In the hippocampus, the activity of ‘ripple’ waves increased at the boundary of events, reflecting their role in segmentation; however, in cortical regions, their presence was higher during the internal development of events.
COORDINATION
According to the researchers, the pattern suggests coordination between the two structures: neocortical regions actively process information, and the hippocampus comes into action when a scene change occurs to «package and consolidate» the memory.
The results reinforce the importance of segmentation and structuring in memory formation, and could have «significant» implications for understanding memory disorders and the development of future therapeutic interventions.