Self-Awareness Activates Particular Brain Centers
Scientists in Germany have found which centers of the brain become active when we are aware of ourselves, the so-called state of "metaconsciousness". Their study, which appears online in the July issue of SLEEP, is the first to show visible evidence of the neural networks that underpin the human conscious state.
They identified them by comparing brain scans of a volunteer during "lucid dream" episodes, to brain scans taken during normal dream states.
The areas they pinpointed as the seat of meta-consciousness belong to a network in the outer layer (cortical) of the brain that includes the right dorsolateral prefrontal cortex, the frontopolar regions and the precuneus.
Some people can have episodes of self-awareness while they sleep and dream. These "lucid dreamers" are aware that they are dreaming, and are also able to control their dreams. During lucid dreaming episodes they can access their memories, perform actions and are aware of themselves, even though they are unmistakeably in a dream state and not awake.
First author Martin Dresler, from the Max Planck Institute of Psychiatry in Munich, explains:
"In a normal dream, we have a very basal consciousness, we experience perceptions and emotions but we are not aware that we are only dreaming. It's only in a lucid dream that the dreamer gets a meta-insight into his or her state."
The human capacity for self-perception, self-reflection and consciousness are some of the biggest unsolved mysteries of neuroscience.
It is not easy to measure which parts of the brain help us do these things. When we are awake, we are self-aware, conscious of what we think and feel. But we can't do this when we are asleep - unless we are lucid dreamers.
One way could be to compare the brains of people asleep with the brains of people awake, or to monitor brain activity while people moved from sleep to wakefulness.
But it is difficult to pick out from these comparisons those precise areas of activity that relate to self-awareness, because, for instance, as people move from sleep to wakefulness there are too many other changes going on in the brain at the same time.
So Dresler and colleagues decided on a different approach: compare brain scans taken during periods of lucid activity with brain scans taking during the normal dreaming that precedes these episodes.
For their study, they recruited four experienced lucid dreamers and invited them to spend the night in a sleep lab while scientists monitored their brain activity using parallel functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) recordings of their night sleep.
Of the four volunteers, one had two episodes of "verified lucid REM sleep" that were long enough to be analyzed by fMRI, said the researchers, who note in their paper that:
"During lucid dreaming the bilateral precuneus, cuneus, parietal lobules, and prefrontal and occipito-temporal cortices activated strongly as compared with non-lucid REM sleep."
Senior author Michael Czisch, head of a research group at the Max Planck Institute of Psychiatry, said:
"The general basic activity of the brain is similar in a normal dream and in a lucid dream."
"In a lucid state, however, the activity in certain areas of the cerebral cortex increases markedly within seconds. The involved areas of the cerebral cortex are the right dorsolateral prefrontal cortex, to which commonly the function of self-assessment is attributed, and the frontopolar regions, which are responsible for evaluating our own thoughts and feelings. The precuneus is also especially active, a part of the brain that has long been linked with self-perception."
Although the results are based on scans from one person, the authors suggest, by making them visible for the first time, their findings show the neural networks of the human conscious state, and confirm suggestions made in other studies.