During sleep, three brain regions work together to strengthen memories, but epilepsy can disrupt that process.
While the brain sleeps, three regions appear to synchronize their activity to strengthen newly formed memories. Researchers at Kennedy Krieger Institute and Johns Hopkins Medicine found that disturbances in this coordination were associated with poorer memory performance in people with epilepsy.
The work is the first human study to directly connect interactions among the orbitofrontal cortex, thalamus, and hippocampus with memory consolidation during sleep. The findings provide a clearer view of how the brain preserves memories overnight and how epileptic activity may interfere with that process.
Sleep links three memory regions
The results offer the first direct evidence that these memory-related regions communicate during sleep in ways that support memory formation. They also show that epileptic spikes can interrupt this coordinated activity, which may eventually help guide efforts to identify, monitor, and treat cognitive problems associated with epilepsy.
“We haven’t understood why patients with epilepsy have problems with memory,” said Dr. Catherine Chu, study co-author and vice president of neurology at Kennedy Krieger and director of child neurology and pediatric epilepsy at Johns Hopkins University. “This helps to close that gap.”
Epileptic spikes interrupt memory coordination
The researchers recorded activity from the orbitofrontal cortex, thalamus, and hippocampus in patients with epilepsy. They examined how several rhythmic patterns of electrical activity, including neural oscillations, sleep spindles, and hippocampal ripples, synchronized across the three regions during sleep.
They then compared the strength of that coordination with each patient’s memory performance. Stronger synchronization was associated with better memory, while epileptic spikes disrupted the activity and coincided with reduced performance.
“Each brain recording contains an extraordinary amount of information, and we use tools from mathematics and statistics to turn that complexity into clear patterns with clinical relevance,” said Mark Kramer, study co-author and professor of applied mathematics and statistics at Johns Hopkins University. “These discoveries are possible only because of our interdisciplinary team, no single discipline could have revealed the whole story.”
Reference: “A hierarchical cascade of sleep rhythms supports motor memory and is hijacked by epileptic spikes in human epilepsy” by Anirudh Wodeyar, Dhinakaran Chinappen, Hunki Kwon, Wen Shi, R. Mark Richardson, Mark A. Kramer and Catherine J. Chu, 30 June 2026, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2517454123
Supported by NIH NINDS R01NS115868 and the Epilepsy Foundation New England Blue Skies Award.
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