Sunday, April 26, 2009

Sleep and Cognitive Performance

The latest issue of Science has this interesting study on how sleep-wake regulation impacts cognition. Here is the abstract:

Throughout the day, cognitive performance is under the combined influence of circadian processes and homeostatic sleep pressure. Some people perform best in the morning, whereas others are more alert in the evening. These chronotypes provide a unique way to study the effects of sleep-wake regulation on the cerebral mechanisms supporting cognition. Using functional magnetic resonance imaging in extreme chronotypes, we found that maintaining attention in the evening was associated with higher activity in evening than morning chronotypes in a region of the locus coeruleus and in a suprachiasmatic area (SCA) including the circadian master clock. Activity in the SCA decreased with increasing homeostatic sleep pressure. This result shows the direct influence of the homeostatic and circadian interaction on the neural activity underpinning human behavior.

And today's Globe has this report on the study. A sample:

Smug early birds take note: Night owls actually have more mental stamina than those who awaken at the crack of dawn, according to new research.

“It's the late risers who have the advantage, and can outperform the early birds,” said Philippe Peigneux, a professor of clinical neuropsychology at the Free University of Brussels in Belgium, who along with co-author Christina Schmidt published the counterintuitive findings in the latest issue of the journal Science.

....The study measured the part of the brain that is home to the circadian master clock that operates according to a day-night cycle. Sleep pressure dampens the circadian signal, and activity in this area decreases the longer the person is awake. The night owls were more resistant to sleep pressure.

Genetics dictate whether someone is a morning person, Prof. Peigneux said, adding that most people are “neutral.” But 15 per cent of the population is an “extreme” early morning or late riser; and another 15 per cent are “moderately evening or morning types.”