'Emotional hangover' may affect our future experiences

Emotional experiences can induce internal brain states - known as emotional "hangover" - that persist for long periods, according to a new study which shows that it influences how we remember and attend to future events. 

"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," said Lila Davachi, associate professor in New York University in the US.

"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," said Davachi. 

Scientists have known for quite some time that emotional experiences are better remembered than non-emotional ones. 

However, researchers in the study showed that non-emotional experiences that followed emotional ones were also better remembered on a later memory test. 

To do so, subjects viewed a series of scene images that contained emotional content and elicited arousal. 

About 10 to 30 minutes later, one group then also viewed a series of non-emotional, ordinary scene images. 

Another group of subjects viewed the non-emotional scenes first followed by the emotional ones. Both physiological arousal, measured in skin conductance, and brain activity, using fMRI, were monitored in both groups of subjects. 

Six hours later, the subjects were administered a memory test of the images previously viewed. 

The results showed that the subjects who were exposed to the emotion-evoking stimuli first had better long-term recall of the neutral images subsequently presented compared to the group who were exposed to the same neutral images first, before the emotional images. 

The fMRI results pointed to an explanation for this outcome. 

Specifically, these data showed that the brain states associated with emotional experiences carried over for 20 to 30 minutes and influenced the way the subjects processed and remembered future experiences that are not emotional. 

"We see that memory for non-emotional experiences is better if they are encountered after an emotional event," said Davachi. 

The study appears in the journal Nature Neuroscience.