There's an old saying: the things you don't know are very often the things you have chosen not to know. And, speaking from the physical standpoint of the human brain, this might not be far from the facts.
When we're awake, our brains receive an almost constant flux of information from sensory signals of constantly fluctuating intensities. For decades, scientists have wondered about the nature of the boundary between signals we detect consciously and the ones that fall below the horizon of conscious awareness, remaining in unconsciousness. And they may have just found that answer.
Scientists say they've discovered a crucial area in the brain's cortex that plays gatekeeper to our conscious awareness, according to a recent study published in the journal Cell Reports.
Imagining physical activity deactivated some parts of the brain
"Information processing in the brain has two dimensions: sensory processing of the environment without awareness and the type that occurs when a stimulus reaches a certain level of importance and enters conscious awareness," said a research investigator named Zirui Huang of the Center for Consciousness Science at Michigan Medicine, in the department of anesthesiology, according to a report from MedicalXpress. Huang and the study's lead researcher Anthony Hudetz, et al., tried to verify the switch event in a portion of the brain known as the anterior insular cortex — which functions as a "gate" between low-level sensory information and higher-level awareness.
The study involved experiments on participants, who were inserted into an fMRI machine and given the anesthetic drug propofol to modify their level of consciousness. Then the researchers asked them to imagine themselves in a game of tennis, strolling down a path or clenching their hand, in addition to various forms of motor activity (like squeezing a rubber ball) — all while the participants fell into unconsciousness as the propofol took hold, and then again as they came to once the drug's effect ended.
Earlier research revealed how mental imagery creates brain activity analogous to neural activity witnessed when humans are actually performing the described activity. When they imagine it happening, the region of the brain that causes motor control still lights up. Additionally, other areas of the brain are deactivated while performing these tasks — to concentrate mental awareness on the necessary physical activity. While the study participants fell into unconsciousness, the deactivations were less frequent — and, once they totally lost consciousness, the brain regions corresponding to the mental imagery tasks also showed no activity.
The anterior insular cortex 'filters' information from conscious awareness
After partially regaining consciousness, the participants' brains showed some activity adjacent to mental imagery — and once fully awake, their brains showed typical activity patterns. In search of a correlation between these different states of consciousness, the scientists found the activation of the anterior insular cortex was active in the switch between the different regions' activations and deactivations. "A sensory stimulus will normally activate the anterior insular cortex. But when you lose consciousness, the anterior insular cortex is deactivated and network shifts in the brain that support consciousness are disrupted," said Hudetz in the MedicalXpress report.
Hudetz also said the anterior insular cortex might function as a filter — enabling only the most significant information to enter conscious awareness. "Whether you can detect a stimulus depends upon the state of the anterior insula when the information arrives in your brain: if the insula's activity is high at the point of stimulus, you will see the image." It might seem difficult to say what benefits will come from this, but there are any number of potential applications for this discovery if the anterior insular cortex does what the researchers think. Imagine the ability to acutely or selectively heighten your conscious awareness in relatively quiet or dark surroundings, or tone down the distractions from an active transit through the city. These are both just speculation, of course, but one interesting capability might be: Total recall of your dreams.