Seizures Follow a Consistent Path Through the Cortex Regardless of Speed

Summary: High-resolution recordings of seizures moving through a mouse brain reveal that neurons fire in a reliable, sequential pattern, showing that seizures are not simply the result of neurons randomly “going haywire.”

Source: Columbia University

Of the estimated 50 million people worldwide living with epilepsy, about one in three do not respond to current medications. To develop more effective therapies, scientists are working to understand how seizures begin and spread within the brain.

New research from Columbia University, published in Cell Reports, provides important insight into that process. By imaging individual neurons as seizures propagated across cortex in awake mice, the research team discovered that neurons activate in a stereotyped, sequential order no matter how quickly the seizure travels. This consistent pattern suggests that seizures reflect organized circuit dynamics rather than a chaotic breakdown of neural activity.

“This is good news,” said the study’s senior author, Dr. Rafael Yuste. “It means that local neural circuits play a crucial role in seizure propagation, and that, by targeting the correct cells, it may be possible to stop or prevent certain kinds of seizures.”

To trigger seizures, the researchers delivered small, localized injections to the cortex of awake mice. One drug increased neuronal excitability, while the other impaired inhibitory interneurons—the cells responsible for restraining and coordinating information flow between neurons. Using high-speed calcium imaging, the team recorded activity at single-cell resolution as seizures spread, allowing them to observe cellular dynamics at a scale roughly 100 times more detailed than typical electrode recordings used in human studies.

Across both experimental models, seizures began in the upper layers of cortex and propagated outward in a wave-like fashion before involving deeper layers. Remarkably, whether an individual seizure lasted about ten seconds or extended to thirty seconds, the route taken by the activity through the network remained the same. Lead author Dr. Michael Wenzel used the analogy of a stretched string: the basic arrangement and relative positions remain the same whether the hands move closer together or farther apart. In the same way, neurons preserved their relative firing order even as the speed of propagation varied.

These observations indicate that seizure propagation is governed by reliable circuit relationships rather than by random, uncoordinated firing. That finding has two important implications. First, it emphasizes the functional importance of local microcircuits—how groups of cells are wired and how they constrain activity flow. Second, it highlights inhibitory interneurons as a potential focal point for therapeutic intervention. Because the experiments showed that impairing inhibition helped trigger pathological propagation, restoring or modulating inhibitory restraint could be a viable strategy for preventing seizure spread.

Dr. Catherine Schevon, a neurology professor at Columbia University Medical Center who was not involved in the work, noted that the role of inhibitory restraint in seizure development has been understudied at micrometer scales. She suggested that these findings could inform future drug development or strategies such as interneuron replacement using stem-cell derived neurons, both of which would aim to restore the balance of excitation and inhibition within local circuits.

The study, titled Reliable and Elastic Propagation of Cortical Seizures in Vivo, lists Jordan Hamm and Darcy Peterka of Columbia University as additional authors, along with Drs. Rafael Yuste and Michael Wenzel.

Funding: This research was supported by the National Institutes of Health and the U.S. Army Research Office.

Source: Kim Martineau — Columbia University
Image source: NeuroscienceNews.com image credited to Horwitz Lab / UW Medicine Seattle (public domain).
Original research: The study appears in Cell Reports.

This work provides a cellular-level view of how seizures propagate and underscores the potential effectiveness of interventions that target specific cell types or restore inhibitory control. While the experiments were conducted in mouse cortex and used pharmacological models to elicit seizures, the consistency of sequential firing patterns reinforces the idea that seizure dynamics can be constrained and perhaps steered by the underlying architecture of neural circuits.