Most people remember emotional events like their wedding day very clearly, but researchers are finding out how the human brain prioritizes emotional events in memory. I don’t know. A study published on January 16, 2023 found that nature human behavior, Joshua Jacobs, associate professor of biomedical engineering at Columbia Engineering, and his team have identified specific neural mechanisms in the human brain. The team demonstrated that high-frequency electroencephalograms in the amygdala, a hub of emotional processes, and the hippocampus, a hub of memory processes, are important in enhancing memory of emotional stimuli. Disruption of this neural mechanism caused by electrical stimulation of the brain or depression impairs memory, especially for emotional stimuli.
Increased prevalence of memory impairment
The increasing prevalence of memory disorders such as dementia highlights the detrimental effects that memory loss has on individuals and societies. Disorders such as depression, anxiety, and post-traumatic stress disorder (PTSD), which can also be characterized by imbalances in memory processes, are becoming increasingly prevalent during the COVID-19 pandemic. Understanding how the brain naturally regulates which information is prioritized for storage and what is lost could open up new therapeutic approaches for enhancing memory in people at risk of amnesia. , or may provide important insights for normalizing memory processes in people at risk of dysregulation.
“Emotional events like the birth of a child are easier to remember than other events around the same time,” says Salman, lead author of the study, who started the project during his PhD in the Jacobs lab at Columbia University. E. Qasim says. engineering. “The brain clearly has natural mechanisms to enhance certain memories., And I wanted to identify it. “
Difficulties in Human Neural Mechanism Research
Most investigations of neural mechanisms are done in animals such as rats. This is because such studies require direct access to http://jacobslab.org/brain to record brain activity and conduct experiments to demonstrate causal relationships such as deliberate disruption of neural circuits. However, it is difficult to observe or characterize complex cognitive phenomena such as consolidation of emotional memory in animal studies.
To study this process directly in humans. Qasim and Jacobs analyzed data from memory experiments performed on patients with epilepsy and made direct intracranial brain recordings for seizure localization and treatment. During these recordings, epileptic patients memorized lists of words, and electrodes placed in the hippocampus and amygdala recorded electrical activity in the brain.
Studying EEG Patterns of Emotional Words
By systematically characterizing the emotional associations of each word using crowdsourced sentiment ratings, Kassim found that participants were more likely to say words like “dog” or “knife” than more neutral words like “chair”. I found that I remembered more emotional words better, such as. Looking at the associated brain activity, researchers found that high-frequency neural activity (30-128 Hz) became more prevalent in the amygdala-hippocampal circuit whenever participants successfully remembered emotional words. We noticed that this pattern was not seen if participants remembered more neutral words or if they did not remember the words perfectly. The researchers analyzed this pattern across a large dataset of 147 patients and found that participants’ enhanced memory for emotional words and high-frequency electroencephalograms in the brain via the amygdala-hippocampal circuit. We found a clear association between prevalence and
“It was very exciting for us to discover this pattern of brain activity that links emotion and memory. Previous research has shown how high-frequency hippocampal activity is important for non-emotional memory. because they are,” Jacobs said. “It quickly led us to think about more general causality. Could using therapeutic interventions to elicit high-frequency activity in this circuit enhance memory at will?”
Electrical stimulation disrupts emotional verbal memory
To establish whether this high-frequency activity actually reflects a causal mechanism, Jacobs and his team developed a unique approach to recreate the kinds of experimental perturbations usually limited to animal studies. was formulated. We first analyzed a subset of these patients who performed a memory task while applying direct electrical stimulation to the hippocampus for half of the words the participants had to memorize. They found that electrical stimulation, with a mixed history of benefiting or diminishing memory depending on usage, clearly and consistently impairs verbal memory, especially emotional ones.
Yuma Mohan, another doctoral student in Jacobs’ lab at the time and co-author of the paper, noted that the stimulation also reduced high-frequency activity in the hippocampus. By knocking out patterns of brain activity, we have provided causal evidence that stimulation selectively reduces emotional memory.
Depression works like brain stimulation
Kassim further hypothesized that depression with dysregulation of emotional memory might act similarly to stimulation of the brain. He analyzed the emotional memory of patients in parallel with the mood assessments they undertook to characterize their mental state. Indeed, in a subset of depressed patients, the team observed a concomitant decrease in emotion-mediated memory and high-frequency activity in the hippocampus and amygdala.
“By combining stimulation, recording, and psychometric assessment, we were able to demonstrate causality to a degree not always seen in studies using human brain recordings,” said the University of Texas Southwestern Medical School of Medicine. Neurosurgeon and scientist Bradley Rega said. center and not the author of the paper. “Because we know that high-frequency activity is associated with neuronal firing, these findings add new dimension to human and animal research on how specific stimuli engage neurons in memory circuits. It paves the way.”
next step
Qasim, now a postdoctoral fellow at the Icahn School of Medicine in Mount Sinai, pursued this research avenue by investigating how individual neurons in the human brain fire during the emotional memory process. doing. Qasim and Jacobs hope that it may also have implications for animal studies investigating how this high frequency of activity is related to norepinephrine, a neurotransmitter associated with attentional processes. .Finally, they hope future research will target the high-frequency activity of the amygdala-hippocampal circuit to enhance and protect memory. -; Especially emotional memory.
Our emotional memories are one of the most important aspects of the human experience, influencing everything from our decisions to our entire personality. What we can do to reduce their memory loss or prevent their mental hijacking is very exciting. “
Salman E. Qasim, lead author of the study
sauce:
Columbia University School of Engineering and Applied Sciences
Journal reference:
Qasim, SE, and others. (2023) Neuronal activity in the human amygdala and hippocampus enhances emotional memory encoding. nature human behavior. doi.org/10.1038/s41562-022-01502-8.
