Sleep memory epilepsy study links brain rhythms to recall problems
Researchers report that coordinated sleep activity in three brain regions supports memory and can be disrupted by epileptic spikes.
By Priya Raghavan · Science Reporter
3 min read
A new sleep memory epilepsy study from Kennedy Krieger Institute and Johns Hopkins Medicine reports that memory strengthening during sleep depends on coordinated activity among three brain regions. The finding matters because the researchers say epileptic spikes can interrupt that activity and are linked with weaker memory performance.
The work was published in the Proceedings of the National Academy of Sciences. Kennedy Krieger Institute said it is the first human study to directly connect interactions among the orbitofrontal cortex, thalamus and hippocampus with memory performance during sleep.
The researchers studied patients with epilepsy and recorded activity in those three areas of the brain. They then compared patterns in the recordings with measures of memory performance, according to Kennedy Krieger Institute.
How does sleep strengthen memory?
The study points to timing between brain rhythms as a key part of memory consolidation, the process by which the brain stabilizes and strengthens memories after learning. Kennedy Krieger Institute said stronger coordination among sleep rhythms across the orbitofrontal cortex, thalamus and hippocampus was associated with better memory.
The team focused on rhythmic electrical patterns known as neural oscillations. Kennedy Krieger Institute said the analysis included sleep spindles and hippocampal ripples, two forms of sleep-related activity examined for how they lined up across the brain regions.
According to the researchers, that coordinated activity appears to support motor memory. The publication describes the process as a hierarchy of sleep rhythms that can be disrupted in people with epilepsy when epileptic spikes occur.
What did researchers find in epilepsy patients?
Kennedy Krieger Institute said epileptic spikes interrupted the coordinated sleep activity seen across the orbitofrontal cortex, thalamus and hippocampus. When those interruptions occurred, memory performance declined, according to the study summary.
Dr. Catherine Chu, a co-author of the study, vice president of neurology at Kennedy Krieger and director of child neurology and pediatric epilepsy at Johns Hopkins University, said the work helps address a gap in understanding memory problems in epilepsy. “We haven't understood why patients with epilepsy have problems with memory,” Chu said. “This helps close that gap.”
The study does not present a treatment. Kennedy Krieger Institute said the findings could help guide future methods to detect, monitor and treat cognitive effects associated with epilepsy.
Why the brain recordings matter
The research used direct brain recordings, which allowed the team to examine activity inside the regions tied to memory during sleep. Mark Kramer, a co-author and professor of applied mathematics and statistics at Johns Hopkins University, said the recordings contain extensive information that requires mathematical and statistical tools to identify clinically meaningful patterns.
Kramer said the findings depended on collaboration across fields. “These discoveries are possible only because of our interdisciplinary team—no single discipline could have revealed the whole story,” he said.
The paper is titled “A hierarchical cascade of sleep rhythms supports motor memory and is hijacked by epileptic spikes in human epilepsy.” Its authors include Anirudh Wodeyar and colleagues, according to the PNAS publication record.
This story draws on original reporting from Medical Xpress.