Network Dynamics during Development of Pharmacologically Induced Epileptic Seizures in RatsIn Vivo

Abstract

In epilepsy, the cortical network fluctuates between the asymptomatic interictal state and the symptomatic ictal state of seizures. Despite their importance, the network dynamics responsible for the transition between the interictal and ictal states are largely unknown. Here we used multielectrode single-unit recordings from the hippocampus to investigate the network dynamics during the development of seizures evoked by various chemoconvulsants in vivo. In these experiments, we detected a typical network dynamics signature that preceded seizure initiation. The preictal state preceding pilocarpine-, kainate-, and picrotoxin-induced seizures was characterized by biphasic network dynamics composed of an early desynchronization phase in which the tendency of neurons to fire correlated action potentials decreased, followed by a late resynchronization phase in which the activity and synchronization of the network gradually increased. This biphasic network dynamics preceded the initiation both of the initial seizure and of recurrent spontaneous seizures that followed. During seizures, firing of individual neurons and interneuronal synchronization further increased. These findings advance our understanding of the network dynamics leading to seizure initiation and may in future help in the development of novel seizure prediction algorithms.

Neocortical pathological high-frequency oscillations are associated with frequency-dependent alterations in functional network topology

“…*Significance at P Ͻ 0.01, which does not meet standard of significance for lower-level covariates; †significance at P Ͻ 0.0001, which was defined a priori as the threshold for statistical significance for level 1 covariates. transition to seizures is marked by a decrease in interneuronal synchrony followed by a late resynchronization phase in hippocampal recordings (Cymerblit-Sabba and Schiller 2010). In their decapitated rat model, Netoff and Schiff used dual-cell patch-clamp techniques while simultaneously measuring network activity within the hippocampus to show that seizures were associated with desynchronization (Netoff and Schiff 2002).…”

GABAergic networks jump‐start focal seizures

“…2Bb). Of interest, desynchronization of principal neuron firing 21 along with an increased activity of putative interneurons 22 was also identified at the transition from interictal to ictal activity in acute models of focal ictogenesis in vivo.…”

Generation of physiological and pathological high frequency oscillations: the role of perisomatic inhibition in sharp-wave ripple and interictal spike generation

“…Second: It seems essential to detect HFOs and multiunit activity in recordings from epileptic patients, since the timing and location of fRIPs proved to be diagnostic concerning the origin of epileptic events. Similarly, the reorganization of multiunit activity [74,75,60] and of HFO structure [20] preceding epileptic activity cannot be detected in the low frequency components of the LFP. Therefore in high sampling rate (over 1 00Hz) recordings should be routinely used in diagnostic measurements of epileptic patients.…”