Memory consolidation during sleep is thought to depend on the coordinated interplay between cortical slow waves, thalamocortical sleep spindles and hippocampal ripples, but direct evidence is lacking. Here, we implemented real-time closed-loop deep brain stimulation in human prefrontal cortex during sleep and tested its effects on sleep electrophysiology and on overnight consolidation of declarative memory. Synchronizing the stimulation to the active phases of endogenous slow waves in the medial temporal lobe (MTL) enhanced sleep spindles, boosted locking of brain-wide neural spiking activity to MTL slow waves, and improved coupling between MTL ripples and thalamocortical oscillations. Furthermore, synchronized stimulation enhanced the accuracy of recognition memory. By contrast, identical stimulation without this precise time-locking was not associated with, and sometimes even degraded, these electrophysiological and behavioral effects. Notably, individual changes in memory accuracy were highly correlated with electrophysiological effects. Our results indicate that hippocampo–thalamocortical synchronization during sleep causally supports human memory consolidation.

Background: Several studies from the US and Europe have shown a population-level decline in serum testosterone in men from 1970's to early 2000's. However, to the best of our knowledge, no study examining population-level decline in testosterone has been published in more recent years. The study objective was therefore to examine secular trends in testosterone levels among Israeli men in the first and second decades of the twenty-first century, Methods: All incident total testosterone performed between1/2006 and 3/2019 among 102,334 male members of a large health organization. Results: A significant (p < 0.001) and prominent trend of age-independent decline in the testosterone levels was recorded during the study period for most age groups.Conclusions: There was a highly significant age-independent decline in total testosterone in the first and second decades of the twenty-first century. The decline was unlikely to be explained by increasing rates of obesity.

Background: Several studies from the US and Europe have shown a population-level decline in serum testosterone in men from 1970's to early 2000's. However, to the best of our knowledge, no study examining population-level decline in testosterone has been published in more recent years. The study objective was therefore to examine secular trends in testosterone levels among Israeli men in the first and second decades of the 21st century, Methods: All incident total testosterone performed between1/2006 and 3/2019 among 102,334 male members of a large health organization. Results: A significant (p<0.001) and prominent trend of age-independent decline in the testosterone levels was recorded during the study period for most age groups. Conclusions: There was a highly significant age-independent decline in total testosterone in the first and second decades of the 21st century. The decline was unlikely to be explained by increasing rates of obesity.

Background Several studies from the US and Europe have shown a population-level decline in serum testosterone in men from 1970's to early 2000's. However, to the best of our knowledge, no study examining population-level decline in testosterone has been published in more recent years. The study objective was therefore to examine secular trends in testosterone levels among Israeli men in the first and second decades of the 21 st century,Methods All incident total testosterone performed between1/2006 and 3/2019 among 102,334 male members of a large health organization.Results A prominent trend of age-independent decline in the testosterone levels for most age groups. The results were highly significant ( Common.EditSubmissionSteps.Transform.EquationText )Conclusions The results show a highly significant age-independent decline in total testosterone that is unlikely to be explained by increasing rates of obesity.