There may be such a thing as an 'emotional hangover,' one study suggests.
Research has shown that highly emotional events - including weddings, childbirth, or the death of a loved one - are more easily remembered in the long term.
The more emotional an experience is, the more accurately and vividly we will remember it - not only minutes after, but years later.
However, could it be that an emotional experience also influences how we process and remember future events? In other words, is there such a thing as an "emotional hangover"?
A team of New York University (NYU) researchers - led by Lila Davachi, an associate professor in NYU's Department of Psychology and Center for Neural Science - set out to investigate whether emotional brain states influence how we remember subsequent, nonemotional experiences.
Studying the impact of emotions on forming future memories
The NYU scientists wanted to see if long periods of emotional arousal can influence future brain states, and, if they do, what impact they have on forming memories of neutral events.
To study this, researchers designed an experiment in which they asked participants to view a series of images that contained emotional content.
The participants were split into two groups. The first group saw the emotional content first, and 10 to 30 minutes later, they also viewed a series of non-emotional, more ordinary images. The other group viewed the nonemotional content first and the emotional scenes afterward.
Participants took a memory test of the images around 6 hours later.
Throughout the experiment, scientists monitored physiological arousal (by measuring skin conductance) and brain activity (using a functional magnetic resonance imaging machine) in both groups.
They hypothesized that the carry-over effects of emotional experiences would manifest in low-frequency amygdala connectivity. Therefore, the researchers also examined whether this type of brain activity, present during emotional memory encoding, was also present during the neutral memory encoding phase in the two groups.
The results were published in the journal Nature Neuroscience.
Emotional states persist, influencing memory formation
As the authors note, previous neuroscientific research has already shown that emotional experiences are better remembered than nonemotional ones.
However, what this new study reveals is that nonemotional experiences are also better remembered in the long run when they follow emotional ones.
The participants who were exposed to emotion-arousing images first performed better on the long-term memory test. They displayed a better ability to recall the neutral images than those who had seen the nonemotional content before the emotional images.
The results of the study showed that emotional brain states carried over for 20-30 minutes and influenced the participants' ability to remember neutral experiences in the future.
"Memory for nonemotional experiences is better if they are encountered after an emotional event," says Davachi.
In the group that saw the emotional content first, the researchers also found similarities between the amygdala connectivity patterns during emotional and neutral memory encoding.
The authors explain that the persistence of emotional brain states has a lingering impact on future memory formation.
"How we remember events is not just a consequence of the external world we experience, but is also strongly influenced by our internal states - and these internal states can persist and color future experiences. 'Emotion' is a state of mind. These findings make clear that our cognition is highly influenced by preceding experiences and, specifically, that emotional brain states can persist for long periods of time."