Q. "My seven year old boy sometimes awakens screaming in the middle of the night. When we go into his room he is sitting straight up in bed, staring straight ahead. We try to calm him down but he isn't even aware that we are in his room. After a few minutes, he goes back to sleep. If we awaken him, he doesn't even know why we're there, as he remembers nothing about his dream."

A. He can't remember his dream because it wasn't a dream. He was having a night terror.

When we first fall asleep, we enter stage one sleep. We then progress through stages two and three until, after about an hour and a half, we enter our the deepest sleep, stage four. Scientists can recognise these stages by our brain-wave (EEG) patterns.

It is interesting to note that we don't dream during any of these stages. If you awaken someone during this time, they probably won't remember anything. The only thing they may say is that they were "thinking".

After stage four we then suddenly shift into a completely different mode of sleep called "rapid eye movement" (REM) sleep. This is when all the dreaming occurs. If you watch someone in this stage, you will see their eyes darting from side to side. We dream for about 45 minutes, and then we go back into non-REM sleep for another hour or so. This pattern continues through the night, with the non-REM stages becoming increasingly lighter. Hence the saying "an hour before midnight is worth two after".

It is when we dream that we can have nightmares. These are usually Hollywood style productions in full colour that seem very real at the time.

Night terrors, on the other hand, occur in stage four sleep. This is also the stage in which sleepwalking and talking occur. The reason they occur is unknown, and most children grow out of them. They may be worse at times of stress.

Hearing your child screaming in terror is distressing to you and the rest of the family, but luckily your child is in no danger. Your best strategy, if you can handle it, is to just leave him be. You've already said that he goes back to sleep on his own. Use the same methods for sleepwalkers as well. Determine that he isn't in danger of falling downstairs or out a window, or any other harm, and he'll soon return to bed.

Children aged from 3 to 6 are usually the ones who experience night terrors. Sometimes they continue for a little longer. Of course they are hard to ignore, but it truly is best not to awaken them. You need your rest too, although it is difficult to sleep through a night terror event.