Connectivity and Neuronal Synchrony during Seizures.

Area of Science:

• Neuroscience
• Epilepsy Research
• Computational Neuroscience

Background:

• Uncertainty exists regarding neuronal firing patterns during seizures, with conflicting evidence on synchrony and heterogeneity.
• Understanding seizure dynamics is crucial for developing effective brain stimulation therapies.
• The hippocampus, with its organized excitatory and inhibitory connections, provides a model to study seizure synchrony.

Purpose of the Study:

• To investigate whether neuronal activity during seizures is ordered along excitatory neuronal connections.
• To determine if epileptogenesis enhances neuronal synchrony and if antiseizure drugs disrupt it.
• To explore the role of anatomical connectivity in the synchrony structure of CA1 pyramidal neurons during seizures.

Main Methods:

• Recorded local field potentials from CA1 pyramidal neurons in kindled rats using microelectrode arrays.
• Evoked seizures via rapid, recurrent hippocampal stimulation.
• Analyzed neuronal firing patterns using cross-correlation, theta phase synchronization, entropy, and event synchronization.

Main Results:

• Neuronal firing patterns were correlated along the lamellar axis, but not the septotemporal axis, during evoked seizures.
• Kindling increased neuronal synchrony along the lamellar axis, while septotemporal synchrony remained low.
• Antiseizure drugs (phenytoin and levetiracetam) significantly decreased neuronal synchrony and theta phase preference.

Conclusions:

• The synchrony structure of CA1 pyramidal neurons during seizures and epileptogenesis is dependent on anatomical connectivity and neural plasticity.
• Neuronal firing during seizures aligns with excitatory connection pathways.
• Targeting neuronal synchrony with closed-loop brain stimulation may offer improved seizure treatment strategies.