The Importance of Sleep
Was your mother just being overprotective when she urged you to "get a good night's sleep"? Not according to researchers at the Karolinska Institute in Stockholm, Sweden. They examined 20 years of data and found that heart attacks went up in the days following the transition to daylight saving time in the spring, when people lose an hour of time overnight. In the fall, when people had an extra hour to sleep, the rate of heart attacks went down. New England Journal of Medicine, vol 359, 1966-1968.
A New Example of Mirror Recognition
Mirror self-recognition has been observed in humans, chimpanzees, dolphins, and elephants—all mammals. Now we can add another species to the list; surprisingly, it is the magpie, a member of the crow family. German researchers marked the birds on the throat with colored paint. Like chimpanzees, they examined the marks in the mirror and tried to remove them with their beaks or their feet. Unlike the chimps, who soon lose interest in the marks, the magpies remain active until they have successfully removed them. The investigators believe the difference is due to the importance of well-preened feathers to the birds' survival.PLoS Biology, Vol 6, e202. In an accompanying video one of the birds attempts to remove the mark, then checks its mirror image to determine success.
Can Sleep Problems Cause Emotional Disorders?
This popular press article reviews mounting evidence that sleep disruption may not be a symptom of emotional disorders but one of the causes. Much of the evidence is correlational, such as sleep difficulties preceding the emotional disorder; however, some of it is more compelling, for example, the remission of ADHD symptoms in some children whose snoring and sleep apnea was improved by removal of the tonsils and adenoids. New Scientist, Feb 21.
Are We Guided by Conscious Decisions?
Personal experience tells us that we make a conscious decision to do something, then we act. But in spite of the clarity of this perception, many neuroscientists question its accuracy. In 1985 a study by Benjamin Libet concluded that the supplementary motor area begins making preparations for a movement 300 ms before the individual experiences a conscious decision to make the movement. The result implied that what we experience as a conscious decision may be just the recognition of an unconscious decision that has already been made. But the subjects had to indicate when the "decision experience" occurred by noting the position of a moving light at the time and then reporting it later; because the lag between the brain activity and the "decision" was so short, a slight error in identifying the light's position could be critical. A new study used a similar procedure, but monitored activity in several brain areas using fMRI. The researchers saw activity in the frontopolar cortex that preceded the conscious decision. The activity predicted whether the subject would press a button with the right or left hand 60% of the time; though the predictions were imperfect, they suggest that the activity represented the actual decision making rather than some general preparation. And, the frontal activity occurred about 10 seconds before the conscious decision, so errors in identifing the time of the conscious experience could not explain the result. The researchers plan other studies using more complex decisions. Nature Neuroscience, vol 11, 543-545.
A Different View of Sleep
This review article takes the position that sleep, rather than being induced by sleep centers, begins in local networks as they fatigue and only later is coordinated by centralized sleep structures. Nature Reviews Neuroscience, Vol 9, 910-919.
