By John Kerin ’20
If you closely observe an MRI of the human brain, you will notice ultra-slow waves that pass through in a heartbeat-like rhythm at approximately 1-second intervals. This pattern was recognized decades ago, however it was thought of as MRI noise and insignificant static until recently. Today, the ultra-slow brainwaves are finally being investigated and scientists are making fascinating observations that are allowing them to assemble a more complete picture of the mysterious biological computer we call the brain.
“Your brain has 100 billion neurons or so, and they have to be coordinated,” says Dr. Marcus Raichle, a professor of radiology at Washington University St. Louis’ Mallinckrodt Institute of Radiology. “These slowly varying signals in the brain are a way to get a very large-scale coordination of the activities in all the diverse areas of the brain. When the wave goes up, areas become more excitable; when it goes down, they become less so.”1
Raichle was one of the first researchers to revisit and examine the ultra-slow brainwave patterns in the early 2000s. His subjects would lay quietly in an MRI machine and relax as their minds wandered. He and his colleagues found that even when we feel that we are doing nothing, our brains continue to use almost as much energy as when we are solving complex math problems.
Newer studies have suggested that these constant, pulsing brainwaves play an important role in consciousness and how we experience the world. They have used the resting-state networks to find areas of the brain that behave differently in healthy people in comparison to people with neurological diseases such as Alzheimer’s and schizophrenia.1
The properties of these mysterious waves are still being worked out. For example, a recent study by Mitra et al. found that when mice were put under general anesthesia, the direction of the ultra-slow waves reversed.2 Furthermore, the direction of these waves was directly correlated to the mouse’s state of consciousness. Understanding these bizarre discoveries will be key in increasing the breadth and depth of our knowledge of human consciousness.
(1)Washington University School of Medicine. “Slow, steady waves keep brain humming: Such rhythmic waves linked to state of consciousness.” ScienceDaily. ScienceDaily, 29 March 2018. <www.sciencedaily.com/releases/2018/03/180329141012.htm>.
(2) Mitra, A., Kraft, A., Wright, P., Acland, B., Snyder, A. Z., Rosenthal, Z., … & Lee, J. M. (2018). Spontaneous Infra-slow Brain Activity Has Unique Spatiotemporal Dynamics and Laminar Structure. Neuron.