Experience-dependent changes in cerebral activation during human REM sleep

The function of rapid-eye-movement (REM) sleep is still unknown. One prevai ling hypothesis suggests that REM sleep is important in processing memory t races. Here, using positron emission tomography (PET) and regional cerebral blood flow measurements, we show that waking experience influences regiona l brain activity during subsequent sleep. Several brain areas activated dur ing the execution of a serial reaction time task during wakefulness were si gnificantly more active during REM sleep in subjects previously trained on the task than in non-trained subjects. These results support the hypothesis that memory traces are processed during REM sleep in humans.