Reorganization of pragmatic language networks in patients with temporal lobe epilepsy

Objective

To investigate the neural networks involved in idiomatic expressions (IE) comprehension in healthy controls and patients with drug-resistant temporal lobe epilepsy (TLE), with a functional magnetic resonance imaging (fMRI) task.

Methods

Thirty-two patients with TLE (left or right) and seventeen healthy controls were evaluated. Activated nodes in the fMRI task were defined as Regions of Interest (ROIs) for a posterior functional connectivity analysis.

Results

All participants completed the task successfully. We found a bilateral fronto-temporal network, lateralized to the right, during IE processing in the overall sample. Compared to controls, patients additionally activated frontal, temporal, and insular areas in both hemispheres. Controls exhibited fewer connections but greater inhibitory connectivity, while the opposite (more connections and increased excitatory connectivity) occurred in patients. Compared to controls, TLE patients recruited additional brain areas on top of the expected bilateral frontotemporal network. The connectivity analysis revealed that controls exhibited more effective inhibitory connectivity, with more modular ROIs. In contrast, patients demonstrated greater excitatory connectivity.

Conclusion

The results suggest compensatory neural recruitment in additional areas in TLE during IE comprehension.

Significance

Exacerbated connections in TLE may reflect the need to recruit alternative regions, resulting in higher costs and lower efficiency of the neural network.