June 12, 2009

Sleep can moderate emotional experiences

The sleeping brain evaluates which emotional experiences should be remembered, U.S. researchers said.

The study also found the sooner sleep followed a learning experience the longer the memory lasted -- even for a mater of months. The study suggests memory improves if learning experiences are staggered across time.

Lead study author Jessica Payne of Harvard Medical School in Boston said they were surprised to find the sleeping brain -- in addition to seeing the enhancement of negative memories over neutral scenes -- showed selectivity within the emotional scenes themselves. Sleep served to consolidate into memory what seemed the most relevant, adaptive and useful about the scenes.

It may be that the chemical and physiological aspects of sleep underlying memory consolidation are more effective if a particular memory is 'tagged' shortly prior to sleeping, Payne said in a statement.

The study included data from 44 college students who encoded scenes with neutral or negative objects on a neutral background and were tested on memory for objects and backgrounds 24 hours later.

Half were randomly assigned to train and be tested between the hours of 7 p.m. and 9 p.m., the other half between the hours of 9 a.m. and 11 a.m. Four months later, participants were once again tested on their memory of the scenes.

The findings were presented at Sleep, the 23rd annual meeting of the Associated Professional Sleep Societies, in Seattle.