What Role Do Brain Waves Play in Regulating Consciousness?

While different brain regions have distinct functional roles, increasingly these are being shown to be linked in a highly coordinated way. One way such coordination takes place is via electrical brain "waves"—synchronised electrical pulses from masses of neurons communicating with each other—whose character varies depending on the state of alertness of the organism in which they occur.

These insights about brain waves have coincided with a shift among some scientists away from a view that reduces the brain to the behaviour of its individual components. For instance, neuroscientist Earl Miller views previous theories about how the brain works as tending to see it as "a giant clock, and if you figure out each gear, you’ll figure out the brain."

In contrast, Miller believes the brain is better understood as "networks interacting in a very dynamic, fluid way," with oscillating brain waves, which he sees as "the most powerful signal in the brain" central to the coordination of such networks. Another neuroscientist, Robert Knight, has a similar viewpoint. He believes that "you’ve got to have a way to get brain areas communicating. What oscillations do is provide a routing mechanism." Importantly, brain waves can carry out such routing extremely rapidly. Such waves may tune out extraneous information by temporarily shutting down unnecessary communication lines.

Brain waves can be categorized by their frequency. Alpha waves (8 to 12 Hz) are dominant during quiet thoughts and in some meditative states; beta waves (13 to 32 Hz) dominate our normal waking state of consciousness when attention is directed towards cognitive tasks and the outside world; and gamma waves (33 to 100 Hz) are the fastest brain waves, and relate to simultaneous processing of information from different brain areas.

One topic that Miller has investigated is the involvement of brain waves in working memory. This form of memory allows us to hold multiple pieces of information in mind—a telephone number, the time of an appointment that day, or a grocery list for our evening meal—from a few minutes to several hours. Miller notes that "working memory allows you to choose what to pay attention to, choose what you hold in mind, and choose when to make decisions and take action. It's all about wresting control from the environment to your own self. Once you have something like working memory, you go from being a simple creature that's buffeted by the environment to a creature that can control the environment."

In one recent study, Miller and his colleagues found that the primate brain uses beta waves to consciously switch between different pieces of information. The findings add to insights that emerged from another study by Miller’s team, which found that gamma waves are associated with encoding and retrieving sensory information. They also found that when gamma waves increased in intensity, beta rhythms decreased, and vice versa.

Previous studies have indicated that beta waves are associated with "top-down" information such as a current goal, how to achieve this, and the rules of a task. This suggests that beta waves determine which pieces of information can be read out from working memory. Miller believes that beta waves act like a signal that gates access to working memory. They clear out working memory, and can act as a switch from one thought or item to another.

Miller’s team have been focusing on the prefrontal cortex, a brain region that has long been suspected to mediate "higher" thought processes. The latest studies indicate that this brain region helps construct an internal model of the world, sending "top-down" signals that convey this model to lower-level regions. Meanwhile, other regions of the brain send raw sensory input to areas of the prefrontal cortex, in the form of "bottom-up" signals.

Differences between the top-down model and the bottom-up sensory information allow the brain to figure out what it is experiencing, and to tweak its internal model accordingly.

This model would explain how attention works—for instance, a person can focus on a particular picture while ignoring a noise in the background. It may also explain how different pieces of information might be juggled around in the brain while we try to solve a problem creatively. It suggests a directing role for the prefrontal cortex in this process, but argues against the idea that this region is all-powerful, for the fact that this brain region requires incoming signals from these other regions shows it is also directed by them.

Play Essential Reads

Infinite Play: Training for the Unexpected

The History and Psychology of Chess

Although brain waves appear to mediate global brain activity in other species, the "culturally mediated" view of the brain I have been developing in this blog predicts a link between human brain wave activity and language, in a way that is not found in other species. Investigating how language affects the coordinating role of different brain waves associated with various aspects of human consciousness is likely to be a fertile area for future studies.

Brain waves display what is known as "non-linear dynamics." Such dynamics occur throughout nature and are distinguished by having no organising centre. This is important given the potential role of brain waves as mediators of consciousness, since this non-linear dynamic behaviour would mean that there is no need for consciousness to be centred in any specific part of the brain, conjuring up visions of a controlling homunculus or soul.

Instead, consciousness would be a property of the whole organ. And it seems entirely feasible that such order out of chaos also operates in an animal brain—say that of your pet dog or cat—explaining how its attention is suddenly taken up by something novel in its environment, whether a squirrel, a tasty snack, or just the sight of you.

However, in humans, superimposed on this mechanism for switching attention from one thing to another, language also surely plays a unique and higher guiding role—acting through brain waves, but doing so in a structured way that can only occur in our species because of the word meaning and grammatical structure that language alone can provide.