2026 ECNP Congress

EP02-2007

Altered default mode, salience and sensorimotor network connectivity in left and right temporal lobe epilepsy: a pilot study

Sena Kiciklar — S. Tunali Aslan · Istanbul Kültür University, Department of Psychology, İstanbul, Türkiye

2026 ECNP Congress

Introduction

Temporal lobe epilepsy (TLE) is increasingly reconceptualised as a condition systematically disrupting large-scale cortical networks beyond mesial temporal pathology [1]. Resting-state functional magnetic resonance imaging (fMRI) has emerged as a powerful non-invasive tool for assessing intrinsic network integrity in epilepsy [2]. Although existing literature documents connectivity alterations across multiple resting-state networks in TLE, the extent to which seizure laterality is associated with the distribution of these alterations remains insufficiently characterised. To comparatively examine resting-state functional connectivity differences across canonical brain networks in patients with left and right TLE, with healthy controls as a reference group [3].

Methods

Resting-state fMRI data from 46 participants were obtained from a publicly available dataset (OpenNeuro, ds004469): healthy controls (HC, n=25), left TLE (LTLE, n=12) and right TLE (RTLE, n=9). Analyses were performed using CONN v22 and SPM. Preprocessing followed the default MNI pipeline (realignment, slice-timing correction, segmentation, normalisation, smoothing FWHM=6 mm). Denoising included aCompCor (5 white matter and 5 cerebrospinal fluid components), 12 motion parameters, scrubbing (framewise displacement>0.5 mm) and band-pass filtering (0.008–0.09 Hz). Group-independent component analysis (G-ICA) extracted 40 components using fast-ICA with GICA3 back-projection. Each component was spatially correlated with eight canonical resting-state network templates (default mode, salience, sensorimotor, visual, language, frontoparietal, dorsal attention and cerebellar); for each network, the component with highest spatial similarity (r>0.30) was selected for second-level analysis. Voxel-level group differences were tested using general linear models, with planned contrasts comparing LTLE versus RTLE, LTLE versus HC and RTLE versus HC. Cluster-level inferences applied a cluster-defining threshold of p<0.001 uncorrected and a cluster-size familywise corrected p-FDR<0.05.

Results

Significant connectivity differences between LTLE and RTLE were observed in three networks. Within the default mode network, four clusters showed lateralisation-related differences: left supramarginal gyrus (-68,-36,+30; t=4.43, p-FDR=0.031) and anterior cingulate (+6,+18,+30; t=4.88, p-FDR=0.031) showed greater connectivity in LTLE, while right and left lateral occipital cortex (+30,-82,+10 and -30,-86,+12; t=-4.66 and -4.61, p-FDR=0.031) showed greater connectivity in RTLE. Within the salience network, two clusters showed greater connectivity in RTLE: right superior parietal lobule (+24,-50,+66; p-FDR=0.003) and posterior cingulate (+12,-30,+42; p-FDR=0.039). Within the sensorimotor network, one cluster in right inferior lateral occipital cortex (+36,-68,+8; p-FDR<0.001) showed greater connectivity in RTLE. Visual, language, frontoparietal, dorsal attention and cerebellar networks showed no significant differences.

Conclusions

This pilot study identified distinct resting-state functional connectivity patterns associated with TLE laterality across the default mode, salience and sensorimotor networks. The default mode network showed differences in opposite directions between LTLE and RTLE, whereas the salience and sensorimotor networks showed unidirectional differences. These preliminary findings contribute to the growing literature on lateralisation-related network alterations in TLE and warrant replication in larger samples. The modest sample size, particularly within TLE subgroups, represents a limitation of this study; future investigations with larger and clinically more diverse cohorts will be needed to confirm and extend these observations.

References

  1. Bernhardt, B. C., Bernasconi, A., Liu, M., Hong, S. J., Caldairou, B., Goubran, M., Guiot, M. C., Hall, J., & Bernasconi, N. (2016). The spectrum of structural and functional imaging abnormalities in temporal lobe epilepsy. Annals of Neurology, 80(1), 142–153. https://doi.org/10.1002/ana.24691
  2. Centeno, M., & Carmichael, D. W. (2014). Network connectivity in epilepsy: Resting state fMRI and EEG–fMRI contributions. Frontiers in Neurology, 5, 93. https://doi.org/10.3389/fneur.2014.00093
  3. Doucet, G. E., Pustina, D., Skidmore, C., Sharan, A., Sperling, M. R., & Tracy, J. I. (2015). Resting-state functional connectivity predicts the strength of hemispheric lateralization for language processing in temporal lobe epilepsy and normals. Human Brain Mapping, 36(1), 288–303. https://doi.org/10.1002/hbm.22628