NEW YORK (Reuters Health) - Adolescent boys who "relax" in the evening after doing their homework by playing a heart-pounding computer game may have trouble sleeping and remembering what they just learned, new research hints.

"The impact of media on children's health and well-being is widely recognized and considered a serious problem," note the investigators. "Our results provide supplementary evidence for a negative influence of excessive media consumption on children's sleep, health, and performance," they say.

The study, described in the journal Pediatrics this month, involved 11 healthy 12- to 14-year-old boys with no sleep complaints and who were taking no medications. On two different experiment days, the boys played an age-appropriate interactive racing computer game called Need for Speed for 60 minutes or watched an exciting video on TV, such as a Harry Potter or Star Trek movie. They did this in the evening, 2 to 3 hours before bedtime.

As part of their experiments, Dr. Markus Dworak and colleagues from German Sport University Cologne performed overnight sleep studies, and before and after visual and verbal memory tests.

The results showed that after playing the interactive computer game, the boys took longer to fall asleep, spent less time in slow-wave sleep -- the type that helps a person form factual memories - and spent more time in stage 2 non-REM sleep - the stage of sleep first crops up right after the initial, "drifting-off" phase of sleep, and precedes deep, slow-wave sleep.

Studies in children have shown that playing interactive video games can lead to significant increases in heart rate, blood pressure and respiratory rate, "and thus a higher arousal state of the central nervous system," the investigators note. Pre- and post-computer game cognitive tests also showed a decline in verbal memory performance after playing the hour-long computer game session.

This is an "interesting" finding, the researchers say, one that suggests that strong emotional experiences, such as playing a computer game or watching a thrilling movie, could decisively impact the learning process.

"Because recently acquired knowledge," they explain, "is very sensitive in the subsequent consolidation period, emotional experiences within the hours after learning could influence memory consolidation considerably."

Watching the movie did not affect memory performance or overall sleep patterns, but it did significantly reduce "sleep efficiency" - actual time spent sleeping versus the total time spent in bed. It's possible, the investigators say, that they picked the wrong movies for the experiment, as none of the boys judged the chosen films as very thrilling to watch.