Functional connectivity of the hippocampus to the thalamocortical circuitry in an animal model of absence seizures

- Functional connectivity (FC) of the hippocampus, thalamus and cortex was investigated before and during absence seizures.
- FC of the thalamus to the sensory/motor cortex increased during absence seizures that was consistent with electrophysiology.
- FC between the hippocampus and thalamocortical network enhanced during absence seizures.
- Involvement of the hippocampus during absence seizures may contribute to cognitive deficits in people with absence seizures.

ObjectiveUsing the gamma-butyrolactone (GBL) rat model of absence seizures, this study investigated the functional connectivity of the hippocampus, thalamus and cerebral cortex before and during absence seizures.MethodsFunctional connectivity between the hippocampus, thalamus and sensory and motor cortecies, were examined by the temporal correlations of the resting state blood-oxygen-level-dependent (BOLD) signal. Functional connectivity between these regions was calculated at baseline, 5 min after saline injection, and at 5, 20 and 52 min after GBL injection. This time interval spans the onset of behaviours including chewing and staring spells associated with GBL-induced absence seizures, along with the onset and suppression of spike-and-wave discharges (SWDs).ResultsOverall there was an increase in functional connectivity across most regions. The functional connectivity generally decreased over time and it returned to baseline 52 min post-GBL injection. Functional connectivity of the thalamus to the sensory and motor cortecies increased during absence seizure. The results revealed enhanced connectivity of the left dorsal hippocampus and the thalamus shortly after GBL injection, which coincided with the appearance of SWDs in this rat model.SignificanceIncreased functional connectivity between the hippocampus and the thalamus suggests that the hippocampus participates in the GBL model of absence seizures. Involvement of the hippocampus during absence seizure has implications for studies into the mechanisms in cognitive impairments in patients with absence epilepsy.

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