Consciousness

[Alan V]

It's known that the prefrontal and cerebral cortex, brainstem, hippocampus, and amygdala are active during dreaming. But it's wrong to say that dreams are 'activating' these areas of the brain. It's probably more correct to say that activity in these areas produce dreams. However, this is not settled science. There's a lot we still don't know.

Boru

According to The Emergence of Dreaming by William Domhoff (Oxford University Press 2018), "REM sleep activation turned out to involve a more specific network [rather than the whole brain], with special emphasis on regions within the medial prefrontal cortex and lateral temporal cortex, as well as more posterior parts of the brain, such as the temporoparietal junction. The deactivation during REM sleep of the dorsolateral prefrontal cortex [DLPFC], which is an important basis for working memory, task-oriented thinking, and the experiencing of emotion, along with the deactivation of the primary sensorimotor cortex and the primary visual cortex, were especially striking." (pages 167-168)

In other words, the executive part of our brain which underlies self-consciousness and working memory, as well as those regions which process incoming information and coordinate outgoing motor commands, are turned off.  What is active is a collection of areas now referred to as the default circuit, which is also active during mind-wandering and day-dreaming while awake, as well as the secondary sensorimotor cortex and the secondary visual cortex, which are involved in creating motor commands and visual imagery in the brain.

While the brainstem does control the dreaming state, it is not itself a conscious part of the brain, so it does not dream.  The amygdala contributes to emotional experiences while dreaming, and can be abnormally activated in dreaming in those who suffer from PTSD.  However, without the DLPFC being activated, our emotional responses in dreaming are often muted.  In other words, we do not react as emotionally to some circumstances in our dreams as we would if they happened in waking.  According to the author, this is one aspect of the cognitive deficiency of the dreaming brain, without all of its functions working.

Interestingly, those people who become blind before the ages of around five to seven do not dream visually, though they dream about other sensory aspects of the world.  Those who become blind later can dream normally even without waking sight.  Studies of the dream reports of children at different ages also support the idea that dreaming is a learned cognitive ability rather than an ability inherent in the brain. We learn to dream in waking, although dreaming overlays an automated housekeeping process controlled by the brainstem.