Fear-specific enhancement of tactile perception is disrupted after amygdala lesion

Tactile perception on one's own face is enhanced when viewing a fearful face being touched – as opposed to just approached – by fingers, compared to viewing other expressions, a phenomenon known as the emotional modulation of Visual Remapping of Touch (eVRT). This effect seems to be related to a preferential activation of the somatosensory system in response to threat. To test the contribution of the amygdala to this mechanism, a group of patients with unilateral lesions to the amygdala, a control group of patients with lesions in the extra-temporal regions, and a group of healthy participants completed an eVRT paradigm. They were required to detect bilateral tactile stimulation on their own cheeks, while viewing fearful, happy, or neutral faces being touched or just approached by fingers. Healthy participants and control patients confirmed that viewing a neutral face being touched – as opposed to just approached – by fingers increases tactile detection on one's own face (i.e., the typical VRT effect) and that this effect is enhanced for fearful faces, compared to neutral and happy faces. However, in patients with amygdala lesion, although the standard VRT effect was preserved for neutral faces, this was disrupted for fearful faces. This result indicates that the preferential activation of the somatosensory cortices in response to threat relies on structural integrity of the amygdala.