An instructor leads a discussion of some material from a psychology class

Interval ចន្លោះពេល                                                     reptile សត្វល្មូន

-          Today, we’re going to review the characteristics of sleep, in both humans and other types of living beings. We talked about this some in the last class, and you should have done the reading, so this should all be clear to you. First of all, what are the main characteristics of sleep? Let’s talk about this diagram. What happens to the human body when a person is sleeping? Uh… can you start this off for us Pam?

-          Well, during sleep, the, um, muscles relax, both breathing and heart rate slow down, and… brain waves change.

-          Exactly. Now let’s look at these drawings of brain wave patterns. Ron, can you explain how brain waves change?

-          I think so. The brain of a person who’s awake and relaxed gives off about ten small waves per second, like in the drawing on the left. But it’s different in deep sleep.

-          What’s different about deep sleep?

-          Well, I think that in deep sleep, the, uh, brain waves become much slower and larger, like in the drawing on the right.

-          Well...you don’t sound quite sure of your answers, Ron, but you’ve got them exactly right. Brain waves are the slowest and largest during the first few hours of a period of sleep. This is called the period of slow-wave sleep. Are brain waves always large and slow during sleep? Nancy?

-          No, um, there are periods of small and fast waves at intervals during a period of sleep. These short and fast waves are similar to the brain waves of a person who’s awake.

-          And what happens to the eyes during these periods of fast brain activity?

-          The sleeper’s eyes move rapidly. This is called” rapid-eye-movement sleep” REM sleep.

-          Yes, Pam, exactly. And what other name does the period of REM, or rapid-eye-movement sleep have?

-          REM sleep is called” dreaming sleeps” because this is when dreaming occurs.

-          OK. Let’s stop for a moment and make sure it’s all clear so far… We’ve seen that when a person sleeps, there are different types of brain-wave activity. There’re periods of large, slow brain waves during deep sleep, and there’re periods of small, far brain waves during REM, or dreaming sleep. Now we’re going to compare human sleep patterns with the sleep patterns of certain animals. What can you tell me about the sleep patterns of animal, Ron?

-          Mammals seem to experience true sleep, with changes in brain-wave patterns. They have periods of dreaming sleep and periods of slow-wave sleep.

-          And what about reptiles and fish? Nancy?

-          Reptiles also experience sleep with changes in brain-wave patterns, but they don’t seem to have periods of dreaming sleep. Fish have periods when they become less aware of their surroundings, but, um, there’s scientific evidence of changes in brain waves.

-          Excellent, Now, Pam, let’s see if you can summarize the information for us. Which type of animals seems to experience changes in brain waves while they’re sleeping?

-          Humans, of course, and also mammals, birds and reptiles. Fish don’t seem to experience changes in brain waves.

-          And what about periods of dreaming?

-          Again, humans, of course, experience periods of dreaming and most mammals seem to experience the same type of dreaming, with periods of dreaming sleep and periods of slow-wave sleep. Birds may experience short periods of dreaming but reptiles and fish don’t.

-          That’s every good. That’s all for today.

Extracted from the book of LONGMAN Preparation Course for the TOEFL Test and translated by Ty Theavy