In vitro ictogenesis is stochastic at the single neuron level

Area of Science:

• Neuroscience
• Epilepsy Research
• Cellular Imaging

Background:

• Seizure initiation (ictogenesis) is poorly understood and a major cause of epilepsy disability.
• In vivo studies of seizure onset lack the necessary cellular resolution.
• Organotypic hippocampal slice cultures offer a model to study epilepsy network dynamics.

Purpose of the Study:

• To investigate seizure initiation mechanisms using advanced calcium imaging in an epilepsy model.
• To identify patterns and evolution of seizure onset zones.
• To determine if specific neurons or network changes drive seizure initiation.

Main Methods:

• Utilized GCaMP7-based calcium imaging in organotypic hippocampal slice cultures from mice.
• Performed chronic imaging of entire hippocampal networks with paired electrophysiology.
• Tracked individual neuron activity longitudinally over weeks.

Main Results:

• Identified three distinct seizure onset patterns: low amplitude fast activity, sentinel spike, and spike burst with fast activity.
• Observed characteristic evolution in onset type and refinement of the seizure onset zone over time.
• Found seizure onset to be stochastic at the single neuron level, indicating non-stereotyped activation sequences.

Conclusions:

• Seizure transitions are driven by network-level changes, not by a few 'bad actor' neurons.
• Network alterations enable widespread neuronal involvement in seizure onset.
• This study provides novel insights into the dynamic nature of epilepsy progression.