EEG analysis reveals reduced seizure activity by optogenetic inhibition of GABAergic interneurons

Among the many cell types involved in epileptogenesis, the GABAergic interneurons are of great interests, largely due to their context-dependent role in controlling cellular excitability and dynamic behavior in seizure. By controlling GABAergic interneuron activity with optogenetic technology, we sought to block seizure activity in the hippocampus in a 4-aminopyridine induced seizure model in mice. This paper introduces an experiment where intracranial electroencephalogram (EEG) was acquired from the hippocampal CA3 area during seizure while the GABAergic interneurons were optically altered. EEG segments during GABAergic interneurons inhibition (Laser ON) was compared to the condition when GABAergic interneurons were not inhibited by the light (Laser OFF). We utilized an adaptive Amplitude Correlation Threshold metric to define certain Seizure Level as a key parameter for epileptic detection. We also quantified the degree of inhibition as an evaluation parameter for the laser-interfered treatment. We found that both the frequency and strength of the ictal events were evidently reduced when the GABAergic interneurons were optically inhibited. This work reveals a novel functional role of GABAergic interneurons in seizure.