Distinct EEG seizure patterns reflect different seizure generation mechanisms
Pariya Salami1, Maxime Lévesque1, Jean Gotman1
1Montreal Neurological Institute and Departments of Neurology and Neurosurgery and of Physiology, McGill University, Montréal, Canada.
Journal of Neurophysiology
|February 6, 2015
Summary
Two distinct seizure onset patterns, low-voltage fast (LVF) and hypersynchronous (HYP), are linked to different neural network activities. This study confirms these patterns arise from distinct pathophysiological mechanisms involving specific neurotransmitter signaling.
Area of Science:
- Neuroscience
- Epilepsy Research
- Electrophysiology
Background:
- Low-voltage fast (LVF) and hypersynchronous (HYP) seizure onset patterns are observed in epilepsy.
- These patterns correlate with specific high-frequency oscillations: ripples (80-200 Hz) in LVF and fast ripples (250-500 Hz) in HYP seizures.
- Distinct transmitter signaling characteristics in neural networks are hypothesized to underlie these seizure patterns.
Purpose of the Study:
- To investigate whether LVF and HYP seizure onset patterns originate from neural networks with different transmitter signaling properties.
- To differentiate the pathophysiological mechanisms underlying LVF and HYP seizure onsets.
Main Methods:
- Rats were induced to have seizures using either 4-aminopyridine (4AP), which enhances glutamatergic and GABAergic transmission, or picrotoxin, a GABAA receptor antagonist.
- Electrodes were implanted in the hippocampus, entorhinal cortex, and subiculum to record electroencephalogram (EEG) activity.
- High-frequency oscillations (ripples and fast ripples) were analyzed during seizure activity.
Main Results:
- LVF seizure onset occurred in 82% of seizures induced by 4AP.
- Seizures induced by picrotoxin consistently exhibited HYP onset.
- 4AP-induced LVF seizures showed higher ripple rates, while picrotoxin-induced seizures had higher fast ripple rates.
Conclusions:
- The findings support the hypothesis that LVF and HYP seizure onset patterns result from distinct pathophysiological mechanisms.
- Different transmitter signaling characteristics likely contribute to the emergence of these two seizure onset patterns.
- This research provides insight into the neurobiological basis of seizure variability in temporal lobe epilepsy.
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