P384 The role of sleep spindles in overnight verbal memory consolidation in temporal lobe epilepsy patients

Abstract

Introduction Declarative memory performance and hippocampal functioning are highly associated. Learning induced memory consolidation results in an increased coupling between mesial temporal lobe, thalamus and frontal areas during sleep, resulting in the increase of sleep spindles and slow wave sleep. Our aim was to investigate the modulatory effect of learning on sleep spindles in temporal lobe epilepsy (TLE) patients and to see whether the association between declarative memory consolidation and sleep parameters are altered. Materials and methods We administered three modified versions of the Rey Auditory Verbal Learning Task to TLE patients (n = 22) on three consecutive nights undergoing video-EEG monitoring. Delayed recall was measured 30 min after learning, memory retention was measured in the following morning. Sleep stages were detected manually, sleep spindles were detected with an automated threshold-cutting method based on individually adjusted slow and fast sleep spindle frequency values. Fast and slow sleep spindle density, duration and amplitude were correlated with both online and offline learning. Results Online learning scores showed positive correlation with slow spindle duration, density and amplitude, and a negative correlation with fast spindle density and duration. On the contrary, memory retention scores showed a negative relationship with slow spindle density, duration and amplitude. Conclusion Our results indicate that learning and overnight memory consolidation related sleep spindles are compromised by the pathological process.