Alteration of the alertness-related network in patients with right temporal lobe epilepsy: A resting state fMRI study

Abstract

Objectives: This study aimed to investigate alterations in the alertness-related network in patients with right temporal lobe epilepsy (rTLE) and explore the functional mechanisms of impaired alertness.

Methods: We recruited twenty patients with rTLE and eighteen matched healthy controls. All participants took a neuropsychological attention network test (ANT) and underwent resting-state functional magnetic resonance imaging (rs-fMRI) scanning. We extracted the alertness-related network using multiple independent component analysis (MICA). Subsequently, we compared the intergroup differences in functional connectivity (FC) of this network. Then, the neuropsychological data were correlated to voxels that showed significant FC differences in patients and controls.

Results: The alertness-related network extracted from the patients was similar to that of the controls, covering the right dorsolateral prefrontal cortex, middle frontal gyrus, parietal lobe, part of the temporal lobe, and left posterior lobe of the cerebellum (p<0.05). Compared to controls, patients with rTLE exhibited decreased FC values in the right inferior parietal lobe (IPL) and angular gyrus (p<0.05). Additionally, increased FC was shown in the right inferior frontal gyrus, Rolandic operculum, middle frontal gyrus, dorsolateral superior frontal gyrus, cuneus, and superior occipital gyrus (p<0.05). Behaviorally, patients with rTLE exhibited longer reaction times (RT) in the no cue (t=-2.07, p<0.05) and double cue (t=-2.28, p<0.05) conditions. However, the alertness effect in patients did not significantly differ from that of controls. Moreover, the alertness effect was negatively correlated with the mean Z-value in the right cuneus, which showed increased FC (r=-0.556, p=0.013) in patients with rTLE. There was no significant correlation in the control group.

Conclusion: Our results demonstrated that alterations in the alertness-related network may contribute to the alertness impairment exhibited by patients with rTLE. Our study may provide new insights into the mechanisms of alertness impairments in rTLE.

Keywords: Alertness; Independent component analysis; Resting-state functional magnetic resonance imaging; Temporal lobe epilepsy.