For this reason, Magnin from the University of Lyon 1 and his colleagues now decided to investigate the processes of falling asleep in 13 very special subjects: They were used to treat epilepsy disease electrodes in the brain, with the help of directly activities in the appropriate regions. The evaluation of the data showed an unexpectedly clear result: in over 93 percent of the measurements, the activity in the thalamus had initially dropped and only then, with an average delay of more than nine minutes, in the cerebral cortex. In addition, this drop in activity not only set in later, it was also slower.
Apparently, the thalamus is sent to sleep earlier than the cerebral cortex by the sleep control centers hypothalamus and brainstem, the scientists write. In this phase, the consciousness can then move freely, so to speak, which leads to the misinterpretation of certain signals and thus to the frequently observed hallucinations. Also, the feeling that it took much longer to fall asleep than it actually was, was probably due to this decoupling. The question remains, how this effect comes about. It is conceivable that the cerebral cortex reacts lazily to the sleep commands than the thalamus and therefore shuts off later. Alternatively, it could also be an active process that performs a previously unknown function.Michel Magnin (University of Lyon 1) et al .: PNAS, online pre-publication, doi: 10.1073 / pnas.0909710107 ddp / science.de - Ilka Lehnen-Beyel advertisement