Even as you listen to my voice, parts of your brain may be asleep.

While middle-school teachers may not be surprised, the idea that parts of our brains are on the dance floor, while other parts are sitting it out, contrasts with conventional wisdom.

Generally, sleep is believed to be governed by circadian rhythms and inner time-keeping mechanisms.

But sleep scientists at Washington State University venture the idea that sleep creeps up on people only after independent groups of brain cells become fatigued.

As these cell groups enter the sleep state, we experience the feeling of dozing off. When enough of them sleep, we sleep.

The concept helps explain sleepwalking, where people can navigate without being conscious of their activities.

Think of a self-conducting orchestra in which most sections play harmoniously, but a few race ahead or lag behind.

The brain-cell groups required for movement and balance during sleepwalking are making music, but those needed for consciousness are face down in the orchestra pit.

The theory also helps answer why some people are sluggish when they first awaken… a condition known as sleep inertia.

As we plod through the early wakefulness, a sufficient number of cell groups are active enough for us to be alert.

But not quite enough are firing for us to embark on complex tasks.

More study will be required for the theory to become widely accepted.

Who knows, some part of your brain may already be sleeping on it!