Sleep increases firing rate modulation during interictal epileptiform discharges in mesial temporal structures

Area of Science:

• Neuroscience
• Sleep Medicine
• Epileptology

Background:

• Epileptic seizures and interictal epileptiform discharges (IEDs) are influenced by sleep and circadian rhythms.
• Limited human data exists on sleep's effect on neuronal behavior during interictal activity.

Purpose of the Study:

• To investigate the impact of sleep stages on neuronal activity during interictal epileptiform discharges in epileptic patients.
• To analyze the relationship between sleep depth and the characteristics of IEDs and neuronal firing patterns.

Main Methods:

• Analysis of electroencephalography (EEG) data from eight epileptic patients with implanted mesial temporal electrodes.
• Sleep staging using polysomnography and video-EEG.
• Automated detection of thousands of interictal epileptiform discharges per patient.

Main Results:

• Both the rate and amplitude of interictal epileptiform discharges increased with deeper non-rapid eye movement (NREM) sleep stages.
• Single- and multi-unit firing rates were coupled with local field potentials, showing increased firing during spikes and decreased activity during slow waves.
• These firing rate modulations intensified during deeper NREM sleep stages, while background neuronal activity decreased in firing rate, bursting, and regularity.

Conclusions:

• Deeper NREM sleep stages significantly modulate neuronal firing and increase the rate and amplitude of interictal epileptiform discharges.
• Sleep profoundly influences the neuronal dynamics underlying interictal activity in epilepsy.
• Findings highlight the critical role of sleep architecture in epilepsy pathophysiology.