Spike density in children with self-limited focal epilepsies affects memory performance and slow wave-spindle...

Precise coupling of slow waves and spindles during non-rapid eye movement (NREM) sleep is crucial for memory consolidation. Children with self-limited focal epilepsies (SelFE) show epileptic spike waves during NREM sleep and often have impaired sleep-related memory. We investigated for the first time how spikes affect slow wave-spindle coupling and its impact on overnight memory.

Fourteen SelFE patients (mean age: 8.7  years) underwent overnight high-density EEG (128 channels) and completed a word-pair memory task before and after sleep. Spikes, spindles, and slow waves were automatically detected. Coupling precision was defined as the ratio of spindles during the ascending versus descending phase of the slow wave. Cluster-corrected topographical correlations examined relationships between spike density, coupling precision, and memory outcomes.

Higher spike density was associated with poorer memory performance in a left centro-parietal region. Better memory was linked to greater coupling precision during the ascending phase in a left centro-frontal area. Increased spike density also correlated with reduced coupling precision in a central region.

Spikes may disrupt thalamocortical activity, impairing slow wave-spindle coupling and memory consolidation.

These findings suggest a mechanistic link between epileptic sleep activity and cognitive deficits in SelFE.