by Gerald Epling
On the way to consciousness
Somewhere between “out there” and “in here”, our brains organize what we hear, and see into distinct items, and arrangements of items. These arrangements might be the face of a friend or the sound of a dove, softly cooing in the evening.
Once inside your brain, light comes alive with activity and patterns. Sounds evoke memories and ideas about what is layered at different regions beyond your personal space. Within your brain, the sense of balance combines with the sense of movement in your arms and legs. This sense of kinesthesia supports graceful movement, and decisive action. Your brain is a busy place.
The brain uses about twenty percent of the entire energy supply of the body. At just over 2% of your body weight, energy dedicated to the brain is remarkably high. The brain is not like a muscle. Somewhere between 60 and 80% of the energy used in the brain is dedicated to signaling. The brain is an area of intense communication. Compared to the amount of information that the brain receives, only a sliver rises to the level of conscious awareness. Estimates of the visual system suggest that very little of what the eyes sense ever reaches consciousness. The numbers look like this. If what the eye sends to the brain is 100% of our visual input then the signals that reach areas of high level processing in the brain are less than 2% of what the eye sees. What reaches consciousness is estimated to be about 1% of the information that reaches areas of high-level processing in the brain. Whatever you think that you are seeing is really an image that has been pieced together in your mind.
When you are relaxed and not focusing on anything in particular, the brain takes over with a series of parallel activities, most of which are inaccessible to the conscious mind. In states of consciousness between light steep and wakefulness there is a lot of activity, especially when we are not paying attention to anything in particular. When we interrupt default activity by focusing on a specific task, the overall level of activity in the brain actually goes down.
How can it be the case that the brain is very active when we are at ease or rest? And how can it be true that brain activity is reduced when we engage in some specific task? Doesn’t focusing on something increase the strain on the brain? Do we ever really use more than a few percent of our potential brain power? These questions may be inspired by brain research that shows pictures of the brain becoming energized in a few areas when a person is given a specific task, such as listening to a sound. These images of brain activation are hard won images that are rarely raw or unedited.
When you look at a brain image you may be seeing a colored image of the flow of oxygen, blood, or glucose consumption in the brain. Glucose is sugar, and sugar is energy to the body. Alternatively, you may be seeing an image of oxygen enriched blood flow in regions of the brain where energy is needed to process what we perceive. These images of energy flow give us an idea of what areas of the brain are needed to do a specific task. Without all of the areas of the brain working in a rhythmic pattern, the ability to sense the world outside and inside is diminished. When the method of imaging is changed to reading the electrical activity in the brain, we see a more complex pattern.
As early as 1929 there were observations of a lot of electrical activity in the unengaged brain. These observations were tied to the use of the EEG or electroencephalograph. Why did it take the decade of the brain (1990-2000), to bring to light the existence of so much activity, including a default network, in the unengaged brain? One reason may be the expectation from a reductionist perspective that the brain is just a well arranged bit of the physical universe that evolved to be occasionally handy. This perspective heavily discounts internal events, introspection, thinking, and other things in favor of a stimulus-response explanation to life. From the stimulus-response perspective, there is no motivation for any activity that is not generated by the environment. No stimulus – no response.
If you never look for baseline activity and the causes of baseline activity, then you will never find patterns in the free-running brain. For a long time the normal activity that occurred during imaging was treated as noise. Scientists know how to get rid of the noise. You just record what is normally going on in your brain and then subtract that noise from what goes on when you are doing something interesting. This approach of subtracting baseline noise from recordings of brain activity has helped us learn something about the specialized abilities of different areas of the brain. By example, this approach helped show that an area of the brain known as the fusiform gyrus is important for recognizing faces. Along the way it was also learned that engaging a specific area of the brain with a specific task often shows less than than a 5% increase over the resting blood flow. However, we don’t know how memories are encoded. We haven’t yet cracked the code of where that image of your friends face is stored in the brain.