Posoidan’s Weblog

Sleep helps people better remember aspects of an emotional event while allowing memory of the background information to fade.

The brain makes adaptive decisions about what to remember and what to forget. To find out the way brain remembers emotional or negative incidents and events while sleeping, researchers from America made 88 college students participate in recall tests after seeing pictures that depicted either neutral subjects on a neutral background like a normal car parked on a street in front of shops or negatively arousing subjects on a neutral background like a badly crashed car parked on a similar street. The participants were then tested individually on their memories of both the central objects in the pictures and the backgrounds in the scenes.

Some of the students viewed the pictures in the morning and took memory recall tests 12 hours later after a full day and no napping. Others viewed the pictures at night; slept for 12 hours, and completed memory recall tests in the morning, while a third group of students viewed the pictures either in the morning or the evening and completed recall tests 30 minutes later.

It was found that the memory for negative objects was enhanced 68 percent by a sleep period compared with 44 percent by a wake period. The participants who stayed awake all day largely forgot the entire negative scene that they had seen, with their memories of both the central objects and the backgrounds decaying at similar rates. But, those who were tested after a period of sleep, memory recall for the central negative objects (i.e. the smashed car) were preserved in detail.