A steady lack of sleep during one\'s teen years may result in lasting brain maturation consequences, U.S. researchers suggest.Dr. Chiara Cirelli, associate professor at the University of Wisconsin-Madison, and colleagues indirectly followed the growth and retraction of synapses -- structures that permit a neuron to pass an electrical or chemical signal to another cell -- by counting dendritic spines, the elongated structures that contain synapses and thus allow brain cells to receive impulses from other brain cells.The researchers compared adolescent mice that were either allowed to be spontaneously awake, allowed to sleep or forced to stay awake -- for 8 to 10 hours.The study, published online in Nature Neuroscience, showed that being asleep or awake made a difference in the dynamic adolescent mouse brain -- the overall density of dendritic spines fell during sleep and rose during spontaneous or forced wakefulness.\"These results using acute manipulations of just 8 to 10 hours show that the time spent asleep or awake affects how many synapses are being formed or removed in the adolescent brain,\" Cirelli said in a statement. \"The important next question is what happens with chronic sleep restriction, a condition that many adolescents are often experiencing.\"The experiments continue, but Cirelli said the outcome cannot be predicted.\"It could be that the changes are benign, temporary and reversible,\" she says, \"or there could be lasting consequences for brain maturation and functioning,\" Cirelli said.