Sleep States Differentiate Single Neuron Activity Recorded from Human Epileptic Mesial Temporal Lobe
Abstract number :
2.036
Submission category :
Year :
2001
Submission ID :
2016
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
R.J. Staba, Neurobiology, UCLA School of Medicine, Los Angeles, CA; C.L. Wilson, Ph.D., Neurology, UCLA School of Medicine, Los Angeles, CA; A. Bragin, Ph.D., Neurology, UCLA School of Medicine, Los Angeles, CA; I. Fried, M.D., Ph.D., Neurosurgery, UCLA S
RATIONALE: Previous studies have demonstrated that the neuronal substrates underlying the generation of distinct sleep states are central determinants in the activation or localization of ictal and interictal epileptiform discharges. Utilizing these state-related modulatory mechanisms, we examined interictal single neuron activity recorded from mesial temporal lobe (MTL) areas capable of generating spontaneous seizures during periods of sleep and waking. Our objectives were first, to characterize single neuron activity during the sleep-wake cycle, and second, to determine if sleep-related changes assist in discriminating differences in neuronal activity recorded from sites ipsilateral to the area of seizure onset compared to contralateral sites.
METHODS: Patients with temporal lobe epilepsy (17) were implanted with depth electrodes to localize the area of seizure onset. Spontaneous single neuron activity was recorded from microelectrodes during continuous 6-8 hour overnight sleep studies. Ten minute epochs of neuronal activity were analyzed during polysomnographically-defined periods of waking (Aw), slow wave sleep (SWS) and REM sleep. Only those single neurons recorded during all 3 states were subjected to firing rate and burst analyses.
RESULTS: MTL single neurons recorded from areas ipsilateral (n=32) to seizure onset discharged at significantly faster rates than contralateral neurons (n=42, 4.5 vs. 2.9Hz, F=6.22, P=.01). Neurons ipsilateral to the area of seizure onset did not demonstrate state-related changes in firing rate. However, contralateral neurons showed a significant reduction in firing rate during REM sleep compared to Aw (P=.004) and SWS (P=.002). The greatest difference in firing rate between neurons recorded ipsilateral to area of seizure onset compared to the contralateral side was observed during periods of REM sleep. The mean burst rate was significantly higher in ipsilateral neurons compared to contralateral neurons (11.9 vs. 5.7 bursts/min, F=5.49, P=.01). Overall, burst propensity was greatest during periods of SWS compared to both Aw (P=.007) and REM sleep (P[lt].0001).
CONCLUSIONS: These data show that MTL neurons increase burst discharge during cortically synchronized periods of SWS, while only those neurons contralateral to seizure onset demonstrated a REM sleep-related reduction in firing rate. Our results suggest that the higher level of neuronal burst firing found in MTL areas ipsilateral to seizure onset may create a lower threshold for ictal discharges.
Support: NIH NS02808 & NS33310