We know from experience that the events in our lives that have had an emotional impact on us are those that we remember most clearly, both those that caused us positive emotions –our wedding, the birth of a child, our first love…–, as well as the situations terrifying. “Emotion consolidates memory. Basically, one forgets everything in life and what is remembered is what excites them”, affirms the prestigious neuroscientist Facundo Manés. However, scientists aren’t sure how the human brain prioritizes these events in memory.
A group of researchers has now discovered a specific neural mechanism in the brain that identifies the information with emotional associations to improve memory. Joshua Jacobs, associate professor of biomedical engineering at Columbia Engineering, and his team have shown that high-frequency brain waves in the amygdala, which is involved in emotional processes, and the hippocampus, which is involved in memory processes, are key to improve memory of emotional stimuli.
Strengthen the memory of people at risk of cognitive decline
When this neural mechanism is disrupted, specific memory for emotional stimuli deteriorates. During the COVID-19 pandemic, the incidence of mental disorders such as depression, anxiety and post-traumatic stress disorder (PTSD), which can throw off memory balance, has increased. Therefore, understanding how the brain organizes the information it prioritizes for storage and which it discards could help develop new therapeutic approaches to strengthen the memory of people who are at risk of memory loss.
“Our emotional memories are one of the most critical aspects of the human experience, affecting everything from our decisions to our entire personality”
“It is easier to remember emotional events, such as the birth of a child, than other events of the same time.” “The brain clearly has a natural mechanism for strengthen certain memoriesand we wanted to identify it,” said Salman E. Qasim, lead author of the study, which has been published in Nature Human Behavior.
A pattern of brain activity that links emotions and memory
Qasim and Jacobs analyzed data from memory tests performed on patients with epilepsy who had undergone direct intracranial brain recording for seizure localization and treatment. During the sessions, these patients memorized lists of words while electrodes placed on the hippocampus and amygdala recorded the electrical activity of their brain.
By systematically characterizing the emotional associations of each word using emotion ratings from multiple sources, Qasim found that participants remembered more emotional words, like “dog” or “knife”, than more neutral words, like “chair”. Looking at the associated brain activity, they found that each time the participants successfully recalled emotional words, the high frequency neural activity (30-128 Hz) became more frequent in the amygdala-hippocampal circuit. When the participants remembered more neutral words, or were unable to recall a word, this pattern was absent.
The researchers analyzed this pattern in a data set of 147 patients and found a clear link between the participants’ improved memory for emotional words and the prevalence in their brains of high frequency brain waves in the amygdala and hippocampal circuitry.
“Finding this pattern of brain activity that links emotions and memory was very exciting for us, because previous research has shown how important high-frequency activity in the hippocampus is for non-emotional memory,” Jacobs said. “It immediately prompted us to think about the broader causal implications: If we trigger high-frequency activity in this circuit, through therapeutic interventions, will we be able to strengthen memories at will?”
“Our emotional memories are one of the most critical aspects of the human experience, affecting everything from our decisions to our entire personality,” Qasim explains. “Any steps we can take to mitigate its loss in memory disorders or prevent its sequestration in psychiatric disorders is very exciting.”