Down-modulation of functional ventral striatum activation for emotional face stimuli in patients with insula damage

TL;DR

This study shows that damage to the insula reduces brain activity in the ventral striatum when viewing emotional faces, especially in patients with left hemisphere damage.

Contribution

The study identifies a specific functional deficit in the left ventral striatum linked to insula damage and emotional face processing.

Findings

Patients with left hemispheric insula damage showed reduced BOLD response in the left ventral striatum during emotional face viewing.

Functional activation in the ventral striatum correlated with the intensity ratings of facial expressions in patients.

Voxel-based analysis confirmed decreased BOLD response in the left ventral striatum was driven by left hemisphere damage.

Abstract

Insula damage results in substantial impairments in facial emotion recognition. In particular, left hemispheric damage appears to be associated with poorer recognition of aversively rated facial expressions. Functional imaging can provide information on differences in the processing of these stimuli in patients with insula lesions when compared to healthy matched controls (HCs). We therefore investigated 17 patients with insula lesions in the chronic stage following stroke and 13 HCs using a passive-viewing task with pictures of facial expressions testing the blood oxygenation dependent (BOLD) effect in predefined regions of interest (ROIs). We expected a decrease in functional activation in an area modulating emotional response (left ventral striatum) but not in the facial recognition areas in the left inferior fusiform gyrus. Quantification of BOLD-response in ROIs but also voxel-based statistics confirmed this hypothesis. The voxel-based analysis demonstrated that the decrease in BOLD in the left ventral striatum was driven by left hemispheric damaged patients (n = 10). In our patient group, insula activation was strongly associated with the intensity rating of facial expressions. In conclusion, the combination of performance testing and functional imaging in patients following circumscribed brain damage is a challenging method for understanding emotion processing in the human brain.

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