By Matt Wood
A new study from the University of Chicago used direct recordings of brain activity from human participants to show how “traveling waves” of activity spread across different regions of the brain to coordinate memory formation and recall. The activity forms distinct patterns, such as spirals and concentric waves, that change depending on what the person was doing, including remembering individual items.
“We’ve known for many years that oscillations or waves of activity happen in the human brain, but here we were able to show that there are actually different spatial patterns of these waves,” said Joshua Jacobs, PhD, Professor of Neurology at UChicago and senior author of the study, which was published in Nature Communications.
A fingerprint of patterns
The researchers used recordings of brain activity from patients with drug-resistant epilepsy who have had electrodes implanted in the brain (typically 100-150 for each person) to help doctors determine the cause of their seizures. During the time the patients were hospitalized while the electrodes were implanted, Jacobs and his team worked with them to perform a series of memory tasks on a laptop.
One task, a “treasure hunt” meant to focus on spatial memory, was like a video game where they navigated an environment and had to remember where different objects were located. In the second task, the patients memorized a series of letters and then had to remember which letters they saw in subsequent sequences.
Brain cells communicate with each other in part by producing electrical signals. When a person thinks about something, like remembering a location or letter, the electrodes capture this activity. Each electrode is about one centimeter square in size and can detect activity in up to one million brain cells each. Combined, the data collected by the electrodes can help paint a picture of neuronal activity as it occurs throughout different regions of the brain.
Anup Das, PhD, a postdoctoral researcher who led the study, used AI, machine learning, and signal processing algorithms to analyze this data. Several distinct patterns emerged. Some waves traveled in straight lines in one direction, or planes, while others formed curling spirals. Some waves propagated in concentric circles from a single source, radiating outward like a broadcast or moving inward like a draining sink.