Have you ever stayed up all night studying for a test? How do you feel the next morning? Tired? Nervous? How is your memory?

New experiments [1] using brain scanning methods have revealed how the brain tries to compensate after sleep deprivation. Neuroscientists in San Diego, CA, used functional magnetic resonance imaging (fMRI) to examine the brains of 13 volunteers. The brain activity of these volunteers was examined after a normal night's rest and after staying up for 35 continuous hours. During the brain scan, the volunteers were tested to see how well they could memorize a list of words.

As expected, the volunteers could not recall as many words when sleep-deprived as they could after a good night's rest. Because the prefrontal cortex is very active when people are awake and it is used during complex cognitive tasks, researchers expected to see reduced activity in this brain region after sleep deprivation. However, brain scans revealed quite the opposite: activity in the prefrontal cortex was greater after 35 hours of sleep deprivation compared with the activity after a good night's rest. Also to their surprise, researchers found that areas of the parietal lobes that were not activated after a normal night's sleep were activated in sleep deprived people.

Image used with the permission of Slice of Life

The researchers think that the prefrontal cortex may increase its activity after sleep deprivation because it is responding to some signal that is telling this brain region to "go to sleep." Moreover, sleep deprivation appears to activate regions of the brain (parietal lobe) not normally involved in memory tasks. This may be a way for the brain to compensate or "pick up the slack" when it is tired. In other words, one part of the brain takes over a function for or helps out another part of the brain.

These experiments may provide valuable information about how the brain compensates after damage and may lead to treatments for neurological disorders such as Alzheimer's disease and Parkinson's disease.