Surprisingly Complex Waves Reveal the Brain's Inner Workings

Surprisingly Complex Waves Reveal the Brain’s Inner Workings Introduction I get out of bed. I walk through the dimly lit hallway, thinking of what’s in my fridge and what I should have for breakfast. With no real effort, I’ve navigated my environment, accessed my memory, and assessed the energetic state of my body, all in the space of a few seconds. How is the brain able to do this? Partly by harnessing electricity. The brain spends about half of its energetic resources maintaining the electrochemical gradients that keep neurons poised and ready to fire at a moment’s notice. This gives the brain an extraordinary level of flexibility in responding to the demands of everyday life. The collective electrical activity of many neurons can be seen as waves propagating through the brain from one region to the next, like the raised arms of enthusiastic spectators at a football game. New lines of research are revealing that these waves are more complex than previously known. Typically measured by electrodes, they have been identified as basic planar waves: simply structured oscillations in neural activity. Neuroscientists have traditionally interpreted this as a bit like the sound of the brain’s engine revving, little more than a sign that it’s working. However, emerging evidence in humans and animals suggests that traveling waves play a central role in how the brain functions. “The work coming out is moving this from ‘Are they relevant?’ to ‘This is a major motif of how the cortex processes information,’” said Earl K. Miller, a cognitive neuroscientist at the Massachusetts Institute of Technology. In a study published in April 2026 in Nature Communications, neuroscientists measured traveling waves of neural activity and observed a menagerie: source waves that appear to emanate from one location, sink waves that converge on a spot, and vortexlike spiral waves. The team, which included Joshua Jacobs and Anup Das from the University of Chicago, found that different behavioral tasks were associated with distinct wave patterns. Courtesy of Joshua Jacobs Neurons can change connections with their neighbors over time, but this usually happens on the scale of days or months. Behavior, however, needs to adapt in seconds. A significant number of neuroscientists now believe these large-scale wave patterns may help to reorganize the brain in real time to meet the behavioral demands of waking life. “Even if the traveling wave was just the result of neurons firing, like the sound of the engine, it still tells us something very interesting about the brain based on what the person is doing,” Jacobs said. “If you see a sound moving in a direction across your engine, it means something in your engine is directionally organized.” Back and Forth As far back as the 1920s, neuroscientists have been measuring the brain’s oscillating electrical activity with electrodes on the surface of the scalp via electroencephalography (EEG). When we pay attention, remember, or sleep, the large-scale frequency of the brain’s electrical activity changes. These various oscillations are commonly known as alpha, beta, gamma, and theta waves, and are measured in hertz. But recording electrical activity from outside the skull limits the fidelity of the information you can gather. Jacobs’ lab specializes in intracranial brain recordings. People with severe epilepsy may have had electrodes placed inside their brain to help locate the source of their seizures. With roughly 100 electrodes placed in a particular brain region, and with permission from the patient, Jacobs and his team are able to capture high-resolution data — across both space and time — as the participants perform various thinking tasks. Jacobs and his collaborator Uma Mohan, who is now a neuroengineer at the National Institutes of Health, were part of a team that used this technique to observe brain activity during memory tasks. In a study published in Nature Human Behavior in 2024, they described waves moving in opposite directions across the brain’s outermost region, the cortex. “They either go back to front or front to back across the brain,” Jacobs said. Jacobs said a good way to understand this result is to think of the waves as showing the direction of information propagation. Visual regions are in the back, and the prefrontal cortex, the “higher-level” memory region, is at the front. If you’re paying attention to what you are looking at, signals are traveling backward from receptors in your eyes to the visual cortex, and then forward into the rest of the brain via the wave to form a memory. “The signature of that is to see waves going from the back of the brain to the front,” Jacobs said. “We thought that was a way the brain was exploiting this organization to switch between encoding and recall memory functions on a rapid timescale, depending on what you need your brain to be supporting,” Mohan explained. Shifting Patterns The 2026 research from Jacobs and Das complicated this picture. It showed that these waves can take on much more diverse shapes, patterns, and ripples, far beyond those created by simple up-and-down and back-to-front movement. In the experiment, the team asked participants to perform two memory tasks. The first was a simple verbal memory exercise, in which they had to recall words they had seen on a screen. The second was a more complex spatial task: They navigated a virtual environment and had to recall the locations of objects they encountered. With the high-resolution method, Jacobs and Das observed two new classes of waves in awake humans for the first time. One, emanating from an area of the cortex, was a concentric wave, like the ripples from a pebble dropped into a lake, or the reverse, in which waves converged on one region. The other was a rotating spiral wave traveling in a clockwise or counterclockwise direction, like a hurricane or a flushing toilet. “We see the rotating wave in the spatial task a little bit more often than the waves we see in the verbal task, which tend to have a simpler structure,” Jacobs said. “This seems to suggest these rotating waves are better for performing more complex memory behaviors.” Researchers have been making intracranial recordings in humans for a long time, Jacobs said, but they often only looked at one electrode at a time, or a handful. This gave an impression of simple waves across the whole outer cortex. Jacobs realized that, if you look at groups of electrodes that are separated by the right distances, the structure and directionality of the waves becomes clearer. Jacobs got in touch with Bard Ermentrout, a mathematical biologist at the University of Pittsburgh who had been looking at similar patterns in mice. Ermentrout thinks the simple wave patterns observed in the past might actually have been part of more complex waves. However, until recently, researchers haven’t had access to electrodes placed in the right locations or at the right spatial scale to catch the larger pattern. “Maybe the planar waves are just the outer arms, where you’re missing the eye of the storm,” Ermentrout, a co-author of the April 2026 paper, said. “In a hurricane you only feel the wind going in one direction. You don’t know that it is spinning unless you’re right there by the eye.” Because the research only collects data from locations where the patients have had electrodes placed as part of their epilepsy treatment, “we might be missing how ubiquitous these patterns really are,” Jacobs said. More Than the Motor Although there is no consensus yet about what these waves in the brain’s local electric field may be doing, some scientists believe they provide another avenue for the brain to coordinate activity between regions. Miller said that these wave patterns are much more dynamic and flexible than the stable, more architectural connections between neurons. For Miller, it makes sense that the brain would exploit this emergent, biophysical layer of organization that shifts and moves on the same timescale as behavior. “The architecture of the brain is really important, and the traveling waves tend to follow the anatomy, but they don’t strictly follow it. … The connectivity is more like the information that’s baked into the brain for long-term storage, and the waves are when that information gets expressed in terms of thought and neural processing,” Miller said. The waves might be relevant to a variety of brain functions. Studies have found evidence that they play a role in sensory processing, prediction, and modulating the underlying excitability of neurons, making them more or less likely to fire when called upon. Pei Zhao A paper published in Science in June 2026 echoes the results found in human epilepsy patients by Jacobs and his team. The neuroscientists Zhiwen Ye of Shenzhen Medical Academy of Research and Translation and Nicholas Steinmetz of the University of Washington also observed circular, rotating waves, but this time in the brains of mice. Fascinatingly, these waves were mirrored and synchronized between the left and right hemispheres. What’s more, in the somatosensory cortex — where information from the senses is integrated with bodily movements — axonal neurons were wired together in a spiraling, circular arrangement. That might facilitate the production of these hurricane-like waves. “What we found was there is a circuit, a connection of cells to form these waves, to mediate these waves,” Ye said. “If they are not important, why would the brain try to wire these cells in this way?” In a review paper published in September 2026 in Neuron, lead authors Lyle Muller of the University of Texas at Dallas and John Reynolds of the Salk Institute for Biological Studies drew on decades of neuroscientific findings to make the case that traveling waves in the visual cortex could help with predicting upcoming sensory information. They described how evolving patterns can carry information about what the brain has just experienced alongside what it is experiencing now to help the brain make short-term predictions about what it is likely to experience next. The waves in the local electric field may play a key role in cognition, Miller said, with the ability to excite or inhibit the underlying neural machinery. He describes neurons in the cortex as “Humpty Dumpty sitting on a wall,” teetering right on the edge of firing. This oscillating electrical activity can alter the voltage gradient at the synapses that connect neurons, making them more or less likely to fire in the future. Not everyone buys the hypothesis that traveling waves in the local electric field play a role in how the brain processes information. For György Buzsáki, a systems neuroscientist at New York University, waves are merely a reflection of what’s going on underneath, at the synaptic level. The more neurons you have, and the more synchronous they are, the stronger the electrical field and the oscillations in it will be. The patterns can tell us interesting things about the circuitry underneath, but that’s about it, according to Buzsáki. “The current that is being generated is done by synapses,” he said. “When current goes into the neuron, they do their computation and generate their action potentials and communicate with each other. You don’t need anything happening in the extracellular space.” Although the true nature of what, if anything, these waves are doing is not fully settled, evidence is mounting that they may be important to how the brain organizes, processes, and expresses information in real time. “Biology exploits regularity and predictability, and these waves are doing organized, predictable things in association with cognitive functions,” Miller said. “If that doesn’t tell you something is going on, I don’t know what does.”