Reduced thalamocortical functional connectivity in temporal lobe epilepsy

Area of Science:

• Neuroscience
• Epilepsy Research
• Functional Neuroimaging

Background:

• The thalamus plays a critical role in the propagation of epileptiform activity in temporal lobe epilepsy (TLE).
• The precise nature of thalamocortical functional connectivity (FC) alterations in TLE and their association with seizure types remain unclear.
• Resting-state functional magnetic resonance imaging (fMRI) offers a method to investigate these brain network dynamics.

Purpose of the Study:

• To investigate the integrity of thalamocortical functional connectivity (FC) in patients with unilateral temporal lobe epilepsy (TLE).
• To determine the relationship between specific seizure patterns and alterations in thalamocortical FC.
• To utilize resting-state fMRI to map these functional changes.

Main Methods:

• Resting-state fMRI data were acquired from three groups: TLE with focal seizures only, TLE with focal and generalized seizures, and matched healthy controls.
• A novel thalamic parcellation method based on FC with five cortical regions was employed.
• Analyses of variance (ANOVAs) compared FC between thalamic segments and cortical seeds across groups.

Main Results:

• Patients with TLE exhibited decreased thalamocortical FC in posterior and ventromedial thalamic segments compared to controls.
• These affected thalamic regions were functionally linked to the parietal/occipital and temporal lobes.
• TLE patients with focal seizures showed FC decreases limited to the ictal hemisphere, whereas those with additional generalized seizures displayed bilateral thalamic FC decreases, particularly involving the dorsolateral pulvinar.

Conclusions:

• This study provides the first evidence of regionally specific thalamocortical FC decreases in unilateral TLE.
• Distinct patterns of thalamoparietal/occipital FC alterations are associated with different TLE seizure types.
• Focal seizure patients exhibit unilateral FC deficits, while those with generalized seizures show bilateral thalamic network involvement.