This is the VOA Special English SCIENCE REPORT.
A new American study offers strong evidence that animals dream about their daily experiences.
Scientists in Massachusetts performed laboratory experiments with four rats. They found that the sleeping rats' brains showed activity that suggested dreaming. The scientists say the animals appeared to be remembering real life events. They say the rats could be using dreams to learn or to memorize, much the way humans do. The publication Neuron reported the findings.
Matthew Wilson of the Massachusetts Institute of Technology in Cambridge organized the study. The scientists placed tiny electrode devices in the brains of the rats. The devices measured activity in a part of the brain called the hippocampus. In humans, the hippocampus is involved in forming and storing memories.
Mr. Wilson and an assistant trained the rats to run through a series of complex passages called a maze. They gave the animals food for successfully completing each run.
The scientists measured the brain activity of the rats while the animals were running through the maze. They also measured brain activity when the rats slept. Experts say animals have the same kinds of sleep periods that people do. They say animals experience periods of rapid eye movement sleep. This is a deep sleep period when people have dreams.
The scientists examined the rats' brain activity during rapid eye movement sleep. They say the brain activity was almost exactly the same as when the animals were running through the maze. The scientists believe the rats were dreaming about running.
Experts have long thought that animals dream. Mr. Wilson says the study suggests that the brains of rats are more complex than had been believed. He says the findings could help scientists better understand how the human mind works.
Some scientists praised the study. They say the technology opens new possibilities for understanding sleep and dreams. Other scientists say the findings support the idea that sleep is important for learning and storing memories. However, still other scientists say more studies and investigation are needed.
This VOA Special English SCIENCE REPORT was written by George Grow.