Impairment of emotional expression detection after unilateral amygdala resection

Abstract

Detecting facial emotional expressions is an initial and indispensable for face-to-face communication. Neuropsychological studies on the neural substrates of this process have shown that bilateral amygdala lesions impaired the detection of emotional facial expressions. However, the findings were inconsistent, possibly due to the limited number of patients examined. Furthermore, this processing is based on emotional or visual factors of facial expressions remains unknown. To investigate this issue, we tested the group of patients (n = 23) with unilateral resection of anterior temporal lobe structures, including the amygdala, and compared their performance under resected and intact hemisphere stimulation conditions. The patients were asked to detect normal facial expressions of anger and happiness, and artificially created anti-expressions, among a crowd with neutral expressions. Reaction times were shorter to detect normal versus anti-expressions when the target faces were presented to the contralateral visual field (i.e., stimulation of the intact hemisphere) than to the ipsilateral visual field (i.e., stimulation of the resected hemisphere). Our findings suggest that the amygdala plays an essential role in the detection of emotional facial expressions, according to the emotional significance of the expressions.