INTERICTAL EPILEPTIC DISCHARGES ASSOCIATED WITH SLEEP SPINDLES IN THE ANTERIOR AND MEDIODORSAL THALAMUS
Orsolya Szalárdy1, 2, Péter Simor1, 3, Péter Przemyslaw Ujma1, 4, Zsófia Jordán4, Csaba Borbély4, László Halász4, Loránd Erőss4, László Entz4, Péter Halász4, Dániel Fabó4, Róbert Bódizs1, 4
Sleep spindles are major oscillatory components of Non-Rapid Eye Movement (NREM) sleep, reflecting hyperpolarization-rebound sequences of thalamocortical neurons, the inhibition of which is caused by the NREM-dependent activation of GABAergic neurons in the reticular thalamic nucleus. Reports suggest a link between sleep spindles and several forms of interictal epileptic discharges (IEDs) which are considered as expressions of pathological off-line neural plasticity in the central nervous system. Here we investigated the relationship between sleep spindles and IEDs in the anterior and mediodorsal nuclei of the thalamus (ANT and MD) of epilepsy patients. Whole-night scalp EEG, and LFP from the ANT MD were recorded from 15 epilepsy patients undergoing Deep Brain Stimulation protocol. ANT and MD slow and fast spindles have been detected using the Individual Adjustment Method (IAM). A subgroup of thalamic, but not scalp spindles was associated with prominent high frequency activity (>30 Hz) in the time-frequency spectra reflecting visually verifiable IED-like waveforms. IED-associated spindles were longer irrespective of frequency (slow or fast). Furthermore, IEDs were more frequently coupled with spindles than with non-spindle NREM segments. The relationship between neuropsychological data and IED-associated spindles was not straightforward. Our findings indicate the involvement of the human thalamus in sleep spindle-related IEDs.