Zebra finches in a University of Chicago lab are providing strong evidence that sleep plays an important role in learning. Researchers have shown that while young birds sleep at night, they may be reviewing the songs they've learned from their parents during the day. The findings were published in the December 18 issue of Science.
Normally, the brain is desensitized to outside stimuli during sleep, partly because of changing concentrations of a neurotransmitter called norepinephrine.
But Daniel Margoliash, associate professor of organismal biology & anatomy, neurobiology and psychology, and two of his graduate students, Amish Dave and Albert Yu, observed an increase in neurological activity during sleep in a region of the zebra finch brain, called the robustus archistratalis (RA), which is involved in singing. It is generally believed that the activity of the sleeping brain helps to consolidate what was learned during the day, but how this occurs has never been directly shown.
"One would expect this area to be quiescent during sleep," says Margoliash, because the birds don't sing in their sleep. But even when the birds were asleep, Margoliash and his students recorded strong, erratic RA activity. RA neurons in wakeful birds exhibit fast, regularly oscillating patterns.
Margoliash and his colleagues recorded electrical impulses from single neurons in the RA of anesthetized, asleep and awake birds as they listened to recordings of their own songs played back on a computer.
Without fail, birds that were asleep or anesthetized exhibited reduced regular oscillations but showed occasional bursts of strong activity in their RA neural impulse patterns. When the birds occasionally woke up during the night, the bursting patterns quickly disappeared and were replaced by the steady oscillating pattern seen during the day.
"This is surprising because the same neurons that show no response during the
day have these strong responses to the bird's own
Contact: Sharon Parmet
University of Chicago