A new study suggests some language learningcan take place during sleep.Researchers from Switzerland's University of Bernsay they discovered people were able to learnnew language words during deep levels of sleep.Results of the study recently appearedin the publication Current Biology.Sleeping hours are generally considered unproductive time.But several studies have suggestedsome learning activity can happen.Studies involving mice provided evidencethat sleep learning is possible in the brain of mammals.Other human studies, the Swiss researchers said,found that simple learning through soundsmay be possible during sleep.But they added that "complex verbal learning"has not yet been demonstrated.Much of the earlier research foundthat memories made when people were awakewere reinforced and strengthened during sleep.This supported the idea that information learned while awakeis replayed and deeply embedded in the sleeping brain.The researchers theorized that,if replay during sleep improves the storage of informationthat is learned while awake,the processing and storageof new information should also be possible during sleep.The research group was led by Katharina Henke,a professor at the University of Bernand founder of the school's Center for Cognition, Learning and Memory.The researchers carried out experimentson a group of young German-speaking men and women.The experiments centered on periods of deep sleep called "up-states."They identified these slow-wave peaksas the best moments for sleep-learning.During normal sleep, human brain cellsare commonly active for a short period of timebefore they enter a state of brief inactivity,the researchers said.The two states are continuously changing.The researchers observed individuals in a controlled environmentduring brief periods of sleep.They recorded brain activity as pairs of wordswere played for the study subjects.One word in the pair was a real German word.The other was a made-up foreign word.For later identification purposes, the German words chosenwere things clearly larger or smaller than a shoebox.Each word pair was played four times,with the order of the words changed each time.The researchers said the word pairs were played at a rhythmthat is similar to actual brain activity during deep sleep.The goal was to create a lasting memory linkbetween the false word and the German wordthat individuals could identify when awake.When the subjects woke,they were presented with the false language words– both by sight and sound.They were then asked to guesswhether the false word played during sleeprepresented an object smaller or larger than a shoebox.During this part of the experiment,some of the subjects had their brain activityrecordedby magnetic imaging technology.This was meant to measure brain activitywhen the subjects were giving their answers to the questions.Results of the study found that a majority of subjectsgave more correct answers about the sleep-learned wordsthan would be expected if they had only guessed at random.The researchers said they measured increased signalsaffecting a part of the brain known as the hippocampus.This brain structure is very importantfor building relational memory during non-sleep periods.The researchers said memory was best for word pairs presentedduring slow-wave peaks during sleep.The study suggests that memory formation in sleepappears to be caused by the same brain structuresthat support vocabulary learning while awake.The researchers say more studies are neededto support their findings.However, the experiments do provide new evidencethat memories can be formed and vocabulary learning can take placein both conscious and unconscious states.