By replaying the day's events in dreams, scientists argue, the brain is able to coalesce information it has taken in during the day and make sense of it. An important difference between sleep studies with humans and birds is how closely scientists are able to monitor the brain. Margoliash was able to track the activity of individual neurons while the zebra finches were both awake and sleeping. He did this by stringing a microwire inside the birds' brains so they were near specific neurons. The wire then fed pulses reflecting the neurons' activity to a recording device.
Scientists studying people's brains during sleep can only dream of such intricate monitoring.
I have very dedicated graduate students but so far no one has volunteered. By tracking the activity of single neurons in the birds brains, the researchers saw that the cells fire in the same patterns when the bird is singing and when it is sleeping and listening to its own song. Those patterns are absent, however, when the bird is awake, not singing and is listening to a recording of its own song. So Margoliash concludes that sleeping is critical for the birds to rehearse their tune. The zebra finch can replay and strengthen the pattern during sleep.