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.

Real‐time effects of interictal spikes on hippocampus and amygdala functional connectivity in unilateral temporal lobe epilepsy: An EEG‐fMRI study

“…Amygdala, a classic common component of both the reward and prefrontal‐limbic systems, can be used as the functional hub to identify the FC‐based reward‐emotion network . Previous studies have shown reduced FC between the amygdala and other nodes of the reward‐emotion network in TLE in the absence of IEDs, which could be linked to emotional disorders such as depression, as well as psychiatric comorbidities of TLE …”

Mapping Epileptic Activity: Sources or Networks for the Clinicians?

“…Facial emotion recognition, particularly for “fear,” is impaired in patients with TLE, especially on the right hemisphere (132–135). Broicher and colleagues (136) showed through fearful-face fMRI-paradigm that the altered amygdala FC in TLE patients is strongly related to the poor performance in behavioral tests evaluating the theory of mind abilities (ability of decoding thoughts and behavior of other human beings). Another study with the same paradigm showed that, in right TLE patients, pre-operative right amygdala activation correlates with post-operative change of anxiety and depression scores [i.e., greater increases in anxiety and depression in patients with greater preoperative activation (137)].…”

Alterations in functional connectivity between the hippocampus and prefrontal cortex as a correlate of depressive symptoms in temporal lobe epilepsy

“…To date, altered FC of the hippocampus [25, 26] and the amygdala [27, 28] has been reported in studies of patients with TLE, but only one study has examined limbic network alterations in depression in TLE [29]. This study revealed regions of decreased and increased FC in depressed relative to non-depressed TLE patients, including decreased FC between the limbic system and prefrontal lobe and increased FC between the limbic system and the angular gyrus.…”