Columbia's astronauts monitored the nerve activity of each exercising rat for the brain study. By evening, three of the four test subjects had completed the course, one at a time.
Rat No. 3 proved to be especially athletic.
"He's been running really well," reported the crew's veterinarian, Richard Linnehan. "He's got over probably 25 runs."
Bruce McNaughton, a University of Arizona psychologist, said his experiment may help explain and ease the disorientation experienced by astronauts in space. The findings also may shed light on the memory loss suffered by the elderly and by victims of Alzheimer's, he said.
"By understanding the basic biology of how this system works, it will give us the understanding we need to be able to tell what is going wrong in this system when it breaks down in normal aging or Alzheimer's disease," McNaughton said.
Each rat, an adult white male, had a caplike device attached to its head a month ago, with 14 electrodes implanted in the portion of the brain known as the hippocampus. In humans, the hippocampus is involved in learning and memory; when damaged, it can result in amnesia. In rats, it seems to involve spatial learning, that is, navigating ability.
For each exercise session, the astronauts plugged a cable into the cap on each rat, enabling them to monitor the animal's brain cell activity on a laptop computer. The brain activity was beamed to McNaughton and his team at Johnson Space Center in Houston.
The three-dimensional, black-and-white track, called the Escher staircase because of its resemblance to the work of the Dutch graphic artist, is designed so the rats can grasp the edges like a ladder and scurry around and around. It also has Velcro strips for the animals to grip.
The track has three bent sides, each less than 2 feet long, and three 90-degree right turns, to disorient the rats.
The rats also scampered on a flat maze that resembles a black-and-white striped X. The maze was flipped periodically to confuse the animals' sense of up and down.
As incentive for running in the right direction, pleasurable sensations were transmitted to the animals' brains via electrodes. Scientists call these sensations "virtual chocolate." No unpleasurable sensations were planned, no matter how uncooperative the rat.
"Purely reward, no punishment in this at all," said University of Texas neurobiologist Jim Knierim.
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