Dynamic and Static Functional Gradient in Temporal Lobe Epilepsy With Hippocampal Sclerosis Versus Healthy Controls.

AIMS: The gradient captures the continuous transitions in connectivity, representing an intrinsic hierarchical architecture of the brain. Previous works hinted at the dynamics of the gradient but did not verify them. Cognitive impairment is a common comorbidity of temporal lobe epilepsy (TLE). Gradient techniques provide a framework that could promote the understanding of the neural correlations of cognitive decline.

METHODS

Thirty patients with TLE and hippocampal sclerosis and 29 matched healthy controls (HC) were investigated with verbal fluency task-based functional MRI and gradient techniques. The correlation between task-based activation/deactivation and healthy gradients, task-based gradients, and dynamic features calculated with sliding window approaches was compared between HC and TLE.

RESULTS

The allegiance in the real data of HC and TLE was more widespread compared to static null models. TLE has lower dynamic recruitment of gradient, atypical activation-gradient correlation, and contracted principal gradient. Correlation analysis proved that the reconfiguration of principal gradient did not drive the reorganization of activation. The atypical activation pattern and impaired recruitment were correlated with cognition scales in TLE.

DISCUSSION: The principal gradient is dynamic. TLE disrupted activation/deactivation patterns, the principal gradient, and the dynamics of the gradient, which were correlated with cognitive decline.