Deeper sleep sign of stronger connections in brain

16 January 2013

Why does one person sleep soundly while another is a light sleeper? Scientists have long understood that the quality of sleep differs dramatically from one person to the next, but the brain mechanisms underlying these differences are little known. Now researchers from the Netherlands Institute for Neuroscience have revealed some of the forces at play in the latest issue of the authoritative Journal of Neuroscience.

Even during sleep, our brains remain active. They produce two types of very specific electrical activity: slow waves and spindles. The more these oscillations occur, the less the sleeping brain reacts to stimulation in the surroundings, such as noise. They can be thought of as the guardians of sleep.

The researchers measured individual differences in the strength of these oscillations throughout the night in fourteen people. They also performed MRI scans in order to determine the quality of the white matter tracts in each individual’s brain. The results show that the strength of a person’s slow waves and spindles depends on the quality of the most important fast white matter tracts connecting the different regions of the brain. These connections function the way motorways do on a road map.

The quality of the white matter tracts is genetically determined to some extent. These findings may also be the first to explain the hereditary nature of an individual’s sleep quality. However, the researchers do not rule out that sleep quality could also contribute to the maintenance and quality of the white matter tracts.

Eus van Someren’s research group has put out a call on the Internet (at www.slaapregister.nl) asking sound and poor sleepers to help them study individual differences in sleep quality, as that is the key to more effective treatment of chronic insomnia, a condition that is not very well understood.

Piantoni G, Poil SS, Linkenkaer-Hansen K, Verweij IM, Ramautar JR, Van Someren* EJ and Van Der Werf* YD (2013) Individual differences in white matter diffusion affect sleep oscillations. J Neurosci 33:227-233, *co-senior authors.