February 9, 2001, Hour 2: Oldest Crystal / Learning and Dreaming

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Science Friday > Archives > 2001 > February > February 9, 2001:

Hour Two: Oldest Crystal / Learning and Dreaming

When you dream, what do you see? Why?

Researchers at MIT have found that lab rats that spend time running mazes appear to dream of their day jobs, and do so in great detail. The scientists measured the signals given off by the rats' brains as they ran the maze, and then monitored the signals again as the rats slept. They found that the signals from when the rat was in the maze matched up very closely with the sleeping signals -- so closely, in fact, that the researchers could pinpoint which portion of the maze the rats were 'dreaming' about by the signals given off by their brains as they slept. The work is reported in the journal Neuron.

Another study, published last October in the journal Science, found that humans also seem to use sleep time to help review new experiences. Robert Stickgold of the Harvard Medical School asked a group of research subjects to play the video game Tetris for hours at a time.

Novice players found that after such Tetris sessions, they began to dream of colorful falling blocks as they drifted off to sleep. Interestingly, several amnesiacs in the study also reported visualizing Tetris blocks - although they had no idea why they might be having such dreams. We'll talk about what all this might mean.

Microscopic view of zircon crystal,
4.4 billion years old.
Photo courtesy John Valley,
University of Wisconsin.

We'll also find out about what scientists are calling the earliest piece of the earth - a zircon crystal dated at 4.4 billion years old. The find is shaking up conventional wisdom about what the early Earth was like -- it may have been much cooler and more hospitable than many geologists once thought. By looking at the ratios of oxygen isotopes in the tiny crystal, the team analyzing the zircon learned that Earth may have had liquid water when the crystal was formed -- not just rivers of magma. We'll find out more.

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Guests:
Robert Stickgold
Assistant Professor of Psychiatry
Harvard Medical School
Boston, Massachusetts

Matthew Wilson
Associate Professor of Biology
Massachusetts Institute of Technology
Cambridge, Massachusetts

John Valley
Professor, Geology and Geophysics
University of Wisconsin
Madison, Wisconsin

Books/Articles Discussed:

"Evidence from Detrital Zircons for the Existence of Continental Crust and Oceans on the Earth 4.4 Gyr Ago." by SA Wilde, JW Valley, WH Peck and CM Graham Nature. 409: 175-178, 2001.

"Temporally Structured Replay of Awake Hippocampal Ensemble Activity during Rapid Eye Movement Sleep" by Kenway Louie and Matthew A. Wilson. Neuron, Vol. 29, 145–156, January, 2001.

"Replaying the Game: Hypnagogic Images in Normals and Amnesics" by Robert Stickgold, April Malia, Denise Maguire, David Roddenberry, Margaret O'Connor. Science, Volume 290, Number 5490, 13 Oct 2000, pp. 350-353.

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