Alterations in functional connectivity of the amygdala in unilateral mesial temporal lobe epilepsy

Abstract

The aim of this work was to evaluate the relationship between ipsilateral amygdala dysfunction in unilateral mesial temporal lobe epilepsy (MTLE) and remote temporal, frontal, and parietal brain structures and to identify their association with theory of mind (ToM) abilities. Functional magnetic resonance imaging (fMRI) data were acquired from MTLE patients with unilateral hippocampal sclerosis (n = 28; 16 left-sided) and healthy controls (HC, n = 18) watching an animated fearful face paradigm. To explore functional connectivity, we used independent component analysis (ICA) of fMRI data to characterize possible amygdala network alterations that may be caused by lateralized amygdala dysfunction. We furthermore investigated the relationship between activation within the amygdala network and ToM task performance. The pattern of amygdalar BOLD activation observed in response to an animated fearful face paradigm was bilateral amygdalar activation in HC and amygdala activation lateralized to the contralateral side in MTLE patients. In HC, a hemispheric asymmetry of the amygdala network was present with amygdala co-activation in predominantly left temporolateral and frontal brain structures. In MTLE patients, the observed asymmetry of amygdala connectivity was modulated by the side of pathology and the extent of amygdalar connectivity to the parahippocampal gyrus and insula was related to ToM test performance. These findings suggest that ipsilateral amygdalar dysfunction in MTLE is associated with alterations in remote temporal and frontal brain areas. The study of psychiatric and neurological disorders via network analysis allows for a shift of focus away from viewing dysfunctions of individual structures to a pathological network that possibly gives rise to a variety of symptoms.