Abnormal functional network connectivity among resting-state networks in children with frontal lobe epilepsy

Abstract

Background and purpose: Epilepsy is considered a disorder of neural networks. The aims of this study were to assess functional connectivity within resting-state networks and functional network connectivity across resting-state networks by use of resting-state fMRI in children with frontal lobe epilepsy and to relate changes in resting-state networks with neuropsychological function.

Materials and methods: Fifteen patients with frontal lobe epilepsy and normal MR imaging and 14 healthy control subjects were recruited. Spatial independent component analysis was used to identify the resting-state networks, including frontal, attention, default mode network, sensorimotor, visual, and auditory networks. The Z-maps of resting-state networks were compared between patients and control subjects. The relation between abnormal connectivity and neuropsychological function was assessed. Correlations from all pair-wise combinations of independent components were performed for each group and compared between groups.

Results: The frontal network was the only network that showed reduced connectivity in patients relative to control subjects. The remaining 5 networks demonstrated both reduced and increased functional connectivity within resting-state networks in patients. There was a weak association between connectivity in frontal network and executive function (P = .029) and a significant association between sensorimotor network and fine motor function (P = .004). Control subjects had 79 pair-wise independent components that showed significant temporal coherence across all resting-state networks except for default mode network-auditory network. Patients had 66 pairs of independent components that showed significant temporal coherence across all resting-state networks. Group comparison showed reduced functional network connectivity between default mode network-attention, frontal-sensorimotor, and frontal-visual networks and increased functional network connectivity between frontal-attention, default mode network-sensorimotor, and frontal-visual networks in patients relative to control subjects.

Conclusions: We found abnormal functional connectivity within and across resting-state networks in children with frontal lobe epilepsy. Impairment in functional connectivity was associated with impaired neuropsychological function.

Fig 1.

Spatial maps of the components identified as resting-state networks. Spatial maps are plotted as T-maps and overlaid on Montreal Neurological Institute 152 template. Top row (from left to right) shows the auditory, frontal, and default mode networks. Second, third, and fourth rows represent the visual, sensorimotor, and attention networks.

Fig 2.

Regions showing group differences in spatial maps for the sensorimotor, attention, and default mode networks, and frontal, auditory, and visual networks.

Fig 3.

Functional network connectivity between resting-state networks. Group comparison of pair-wise independent components shows reduced FNC (solid line) between DMN-attention (IC4-IC65), frontal-sensorimotor (IC46-IC12), and frontal-visual (IC46-IC52) networks in patients and increased FNC (dotted line) between frontal-attention (IC40-IC65), DMN-sensorimotor (IC50-IC60), and frontal-visual (IC40-IC63) networks in patients relative to control subjects.