Evolution of Network Synchronization during Early Epileptogenesis Parallels Synaptic Circuit Alterations

Area of Science:

• Neuroscience
• Epilepsy Research
• Systems Neuroscience

Background:

• Secondary epilepsy arises from a seizure-prone neural network developing after brain injury.
• The precise evolution of these networks during the latent period and after seizure onset remains largely unknown.
• Recent findings suggest network changes continue even after seizures begin.

Purpose of the Study:

• To investigate the dynamic evolution of neuronal networks during early epileptogenesis.
• To characterize changes in neuronal activity and network connectivity following brain injury.
• To understand the synaptic remodeling processes contributing to seizure onset and spread.

Main Methods:

• Utilized sequential calcium imaging of neuronal activity in mouse hippocampal slices.
• Focused on the pyramidal cell layer in in vitro preparations.
• Analyzed neuronal participation in interictal activity, seizure recruitment, neuronal activity correlations, and functional connectivity.

Main Results:

• Observed rapid increases in the fraction of neurons participating in interictal activity early in epileptogenesis.
• Detected more gradual increases in individual neuron recruitment into developing seizures.
• Found increasing pairwise neuronal activity correlation with distance and enhanced network functional connectivity over time.
• Demonstrated continued synaptic remodeling in epileptic networks beyond the latent period.

Conclusions:

• Epileptic network evolution persists beyond the initial seizure onset.
• Early seizures involve largely polysynaptic recurrent excitatory pathways.
• Ongoing synaptic remodeling after epilepsy onset enhances intranetwork connectivity.
• This remodeling facilitates seizure onset and propagation.