How the brain performs this process has remained unclear -- until now. We were able to prove for the first time that REM sleep is indeed critical for normal spatial memory formation in mice," explains Williams, whose team is also part of the CIUSSS de l'Ouest-de-l'Île-de-Montréal research network. Williams co-authored the study with Antoine Adamantidis, a researcher at the University of Bern's Department of Clinical Research and at the Sleep Wake Epilepsy Center of the Bern University Hospital.