Asked by: Tasha Henson, Norwich
The whole brain is active during dreams, from the brain stem to the cortex. Most dreams occur during REM (rapid eye movement) sleep. This is part of the sleep-wake cycle and is controlled by the reticular activating system whose circuits run from the brain stem through the thalamus to the cortex.
The limbic system in the mid-brain deals with emotions in both waking and dreaming and includes the amygdala, which is mostly associated with fear and is especially active during dreams.
The cortex is responsible for the content of dreams, including the monsters we flee from, the people we meet, or the experience of flying. Since we are highly visual animals the visual cortex, right at the back of the brain, is especially active, but so are many other parts of the cortex.
Least active are some parts of the frontal lobes, and this may explain why we can be so uncritical during dreams, accepting the crazy events as though they are real – until we wake up.