When the heart misfires, one electrical pattern worries cardiologists most: a wave of excitation circling the heart muscle, driving contraction wherever it goes, loop after loop—fibrillation. The defibrillator exists to break such rotating waves. Rotating waves have long meant loss of control, an impression inherited from cardiology that has also haunted brain science.
On September 30, Quanta Magazine reported on a development rewriting that impression: researchers have systematically observed rotating spiral waves on the surface of the awake human cortex—and their timing is telling. They appear frequently precisely when you are performing demanding cognitive tasks. In the heart, a rotating wave is an alarm. In the brain, this swirling ring may be a gear-shifting machine.
Why Put Electrodes in the Brain
Start with the method, because everything here came from it. Scalp EEG—the wet cap from a routine checkup—records the summed average of billions of neurons' signals, spatially blurred like watching rain through frosted glass. Too coarse. The lab of Joshua Jacobs at the University of Chicago took another route: epilepsy patients, to locate their seizure foci, already receive intracranially implanted electrodes—roughly a hundred contacts per brain region. While patients lay in bed doing memory tasks, researchers obtained millisecond-scale, millimeter-scale recordings from the cortical surface as a byproduct.
The old way of reading these data was one electrode at a time. Jacobs realized that treating a cluster of adjacent electrodes as a small 'map' would reveal the waves' spatial shapes—much as staring at a single patch of spray never reveals an ocean current's vortex. With this shift in perspective, two previously unseen wave types took shape.
Two New Waves, and When They Appear
The first is the concentric wave: activity spreading outward from a point on the cortex, like a pebble dropped in a basin—or converging inward, like raindrops flowing the wrong way up an umbrella. The second is more striking: the spiral wave, electrical activity circling a center, clockwise or counterclockwise, spinning like a hurricane on a weather-satellite image.
Wave shape matches the task. During complex spatial memory tasks, spiral waves appear significantly more often; during simple verbal recall, unremarkable planar waves dominate. Another class of waves shuttles between frontal and posterior cortex, and flipping its direction corresponds to the brain shifting gears between 'storing memory' and 'retrieving memory.' Waves are not the shape of background noise—they change with what you are doing.
Nor is this a one-lab finding. In 2024, Jacobs and Uma Mohan, now at NIH, reported bidirectional traveling waves during memory tasks in *Nature Human Behaviour*. This April, in *Nature Communications*, Jacobs, Anup Das, and mathematical biologist Bard Ermentrout and colleagues presented a full taxonomy of complex waves in the human cortex. In June, *Science* carried a more dramatic picture from Zhiwen Ye (Shenzhen Medical Academy of Research and Translation) and Nicholas Steinmetz (University of Washington): in the mouse brain, two spirals rotating in mirror-synchrony, one per hemisphere—an arrangement matching the fact that somatosensory cortex axons are anatomically wired along spirals. In September, a *Neuron* review by Muller and Reynolds proposed that visual cortex waves may support the brain's short-term prediction.
The Storm's Eye—and the Skeptics
At the mechanistic level, MIT cognitive neuroscientist Earl Miller offers an image: cortical neurons are like egg-shaped Humpty Dumpties perched on walls, teetering near firing threshold. A traveling wave passing by nudges some off the wall—firing—or pulls them back. In this view, genes and connections are the long-term wiring; waves are the improvising conductor deciding which brain regions are on duty right now.
Skeptics persist, loudest among them György Buzsáki of NYU. His position is blunt: waves are byproducts of underlying synaptic currents, like a machine's vibration—nothing functional happens in the extracellular space. The wave spins because the circuit below is working; the wave itself does nothing. Evidence on both sides keeps accumulating.
Mathematician Ermentrout's remark may be the best current reconciliation: past planar waves may simply have been the overlooked periphery of spiral waves—decades spent staring at the storm's arms without seeing its eye.
One clarification: this research reads fluctuations in the local electrical field, not the textbook alpha/gamma EEG frequency bands; band details are omitted here for clarity. Whether these waves are the engine's vibration or its throttle, no one can yet say. The cardiac precedent reminds us that rotating waves can be either loss of control or a pump. Where the brain's pump sends its flow, the answer is still inside the skull.