Deep brain stimulation could be used to reduce the emotional strength of a person鈥檚 memories and may one day even help tackle post-traumatic stress disorder.
at Icahn School of Medicine at Mount Sinai in New York and his colleagues investigated the link between emotion and memory by reanalysing data from a . 鈥淲e really wanted to understand how the brain kind of naturally enhances memory for certain events over others,鈥� says Qasim.
In the study, 148 people with epilepsy had been asked to memorise 12 words in quick succession and then recall as many as possible, repeating this task 20 times with different words. Each participant had pre-existing electrodes implanted in their brain for seizure monitoring. Researchers used these to track their brain activity during the task.
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In this reanalysis, the team ranked the emotional strength of each word used in the study, based on crowdsourced data. For example, words like dog and hurricane rank as highly emotional, while purse is one of the least emotional.
The researchers found that more emotional words were more likely to be remembered, and those that were recalled were also associated with increased high-frequency activity in the brain. Higher rates of this activity have previously been linked to a rise in the firing rate of the amygdala, which is thought to play a key role in emotion.
As part of the original study, 19 participants consented to undergo deep brain stimulation (DBS). The researchers found that when the stimulation targeted participants鈥� hippocampi 鈥� which plays a major role in memory 鈥� while they memorised words, they no longer remembered emotional words more than others. The average recall rate of 40 per cent for the most emotional words dropped to 28 per cent in this cohort, says Qasim.
To make sure this fall in recall rate wasn鈥檛 simply because DBS disrupts memory recall in general, the researchers also looked at other measures of recall used in such memory tasks. For example, the first word in a list is usually remembered better than other words, says Qasim, and DBS had no impact on this.
The researchers also found that emotional words were less likely to elicit increased high-frequency activity in the brain during DBS. Qasim speculates that DBS may be disrupting the process in which the brain typically tags memories as emotional and makes them easier to remember.
He says the study could point to a novel way to treat post-traumatic stress disorder (PTSD). 鈥淎 lot of therapies for PTSD centre around getting people to detach from pathological emotional memories,鈥� he says. 鈥淭his method could be used to do that also.鈥�
But DBS is not without downsides. Team member at Columbia University in New York says DBS has many potential risks including infection and tissue damage. 鈥�Thus, at least at this stage, DBS methods for cognition should be considered highly experimental,鈥� he says.
鈥淭his work provides exciting new evidence that the formation of emotional memories can be disrupted,鈥� says at Boston College in Massachusetts. 鈥淚n many affective disorders, the brain prioritises access to negative memories, and these negative memory biases can be harmful to daily function.鈥�
鈥淭here could be great promise to finding ways to dial down the salience of emotional memories, allowing individuals to view their past through a less negative lens,鈥� she says.
Nature Human Behaviour
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