 A well known hypothesis for sleep:  the reprocessing and consolidation of memory traces  Brain areas reactivate during REM sleep  Shown by PET scans in human subjects after implicit learning tasks  Reactivations may reflect reprocessing of memory traces  The functional connectivity of the reactivated brain regions are examined

 The left premotor cortex shows an increase in functional connectivity with both the:  Left parietal cortex (Brodmann area 7)  Bilateral pre-SMA (Brodmann area 6)

 Healthy, right-handed males (22.9±3.5 years old)  Group A (trained):  6 subjects learned a serial reaction time task on day 1  The following day they performed it again  12 PET/MRI scans were performed on the subjects while they slept

 The PET sleep scans were only performed when polysomnography showed steady sleep patterns  Group B (untrained):  5 subjects followed the same protocol but did not do the SRT training

 Parietal cortex (left) and pre-SMA (right) showed a significant increase in functional connectivity with the premotor cortex during REM in trained versus untrained subjects

 Regional cerebral blood flow graphs (rCBF)  Blood supply to the brain at a given time  Regression of rCBF in the premotor cortex and the parietal and pre-SMA  Post Training REM denoted as RED  REM from untrained subjects denoted as GREEN

 Comparison of REM sleep in trained vs. untrained subjects:  In trained subjects, the premotor cortex experiences an increased functional connectivity with both the:  Parietal Cortex  Pre-SMA

 Cerebral areas reactivated during post-training sleep do not act in isolation  Mental pathways are active and are being refined  Reactivation reflects the recruitment of a large-scale neuronal network caused by a new environmental situation

 Increased function connectivity between visuo- motor areas and motor behaviour areas  Supports the hypothesis that the neural network is refined after implicit learning  Results support the hypothesis that memory traces are processed during subsequent sleep

 More evidence that SLEEP IS IMPORTANT  Utilization of new technology  The combination of PET/MRI scanning  Polysomnography  Implicit memory is refined, what about explicit memory?  What about slow wave sleep? Could it contribute to the consolidation of memory traces?

 Laureys et al. (2001) Experience-dependent changes in cerebral functional connectivity during human rapid eye movement sleep. Neuroscience 105(3):521-5.