Good Sleep Helps Consolidate and Strengthen New Memories

In a recent article published in Science Magazine, researchers from NYU Langone Medical Center have shown that sleep after learning encourages the growth of dendritic spines, tiny protrusions that connect brain cells and facilitate the passage of information across synapses. The laboratory  research, conducted on mice, concludes that the activity of brain cells during deep or slow-wave sleep after learning is critical for such growth.

These findings provide important physical evidence to support a hypothesis that sleep helps consolidate and strengthen new memories, and they show how learning and sleep can cause physical changes in the motor cortex, a brain region responsible for voluntary movements. 
It is well known that sleep plays an important role in learning and memory, but the underlying physical mechanism responsible weren't understood until now. On the cellular level, brain cells that spark as we digest new information during waking hours "replay" during slow-wave sleep, when the brain waves slow down and rapid-eye movement and dreaming stop. Scientists have long believed that this nocturnal replay helps us form and recall new memories, yet the structural changes of this process have remained poorly understood.



The scientists employed mice which had been genetically engineered with a fluorescent protein in their neurons. Using a special laser-scanning microscope that illuminates the fluorescent proteins in the motor cortex, they were then able to track and image the growth of dendritic spines along individual branches of dendrites both before and after the mice learned to balance on a spinning rod.
They trained two sets of mice: one set spent an hour on the spinning rod and then slept for 7 hours: the second trained for the same period of time but was kept awake for 7 hours. The sleep-deprived mice experienced significantly less dendritic spine growth than the well-rested mice.

The scientists also showed that brain cells in the motor cortex that activate when mice learn a task reactivate during slow-wave deep sleep. Disrupting this process prevents dendritic spine growth. Their findings offer an important insight into the functional role of neuronal replay -the process by which the sleeping brain rehearses tasks learned during the day- observed in the motor cortex.

http://www.sleepreviewmag.com/2014/06/sleep-after-learning-enhances-memory-brain-changes/