Topographical reorganization of brain functional connectivity during an early period of epileptogenesis

Abstract

Objective: The current study aims to investigate functional brain network representations during the early period of epileptogenesis. Methods: Eighteen rats with the intrahippocampal kainate model of mesial temporal lobe epilepsy were used for this experiment. Functional magnetic resonance imaging (fMRI) measurements were made 1 week after status epilepticus, followed by 2-4-month electrophysiological and video monitoring. Animals were identified as having (1) developed epilepsy (E+, n = 9) or (2) not developed epilepsy (E−, n = 6).Nine additional animals served as controls. Graph theory analysis was performed on the fMRI data to quantify the functional brain networks in all animals prior to the development of epilepsy. Spectrum clustering with the network features was performed to estimate their predictability in epileptogenesis. Results: Our data indicated that E+ animals showed an overall increase in functional connectivity strength compared to E− and control animals. Global network features and small-worldness of E− rats were similar to controls, whereas E+ rats demonstrated increased small-worldness, including increased reorganization degree, clustering coefficient, and global efficiency, with reduced shortest pathlength. A notable classification of the combined brain network parameters was found in E+ and E− animals. For the local network parameters, the E− rats showed increased hubs in sensorimotor cortex, and decreased hubness in hippocampus. The E+ rats showed a 1232 | LI et aL.

Probing hippocampal stimulation in experimental temporal lobe epilepsy with functional MRI

“…The response in these regions was also stronger compared to the healthy controls, indicating increased functional connectivity in the epileptic brain, which has also been found in rodent models of TLE by resting-state fMRI [57,58]. Stimulations at 40 and 100 Hz elicited clear responses in cortical, frontal and prefrontal areas.…”

Small loci of astroglial glutamine synthetase deficiency in the postnatal brain cause epileptic seizures and impaired functional connectivity

“…A recent study of the rodent intrahippocampal kainic acid model of epilepsy demonstrated connectivity alterations with increased global connectivity and both decreased and increased local connectivity in epileptic animals. 43 This stands in contrast to reports that found decreases in global measures of connectivity directly related to seizure frequency. 32,44 A recent human study also found decreased global functional connectivity in patients with mesial temporal lobe epilepsy, where the reduction is suggested to bear a direct relationship to neurocognitive deficits.…”

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“…In this study, fMRI and graph-theoretic approaches were used to understand the changes in network connectivity in the rodent brain following unilateral intra-hippocampal kainic acid injection. 7 By comparing rats that develop epilepsy (E+) with those that did not develop epilepsy (E−) with the same insult, the goal of this study was to identify and distinguish connectivity changes in epileptogenesis using fMRI. With 40 nodes representing brain regions and edges for functional connectivity, this study performed global and local connectivity analyses.…”