The perception of tactile stimuli on the face is modulated when subjects concurrently observe a face being touched; this effect is termed “Visual Remapping of Touch”, or the VRT effect, and might represent a visually evoked somatosensory activity. VRT effect is modulated by specific key information processed in face-to-face interactions: facial emotional expression. Indeed, tactile perception in healthy subjects is enhanced when viewing touch towards a fearful face compared to viewing touch towards neutral, happy or angry expressions. The fear-specific modulation of the VRT effect might be interpreted as an adaptive preferential enhancement of the somatosensory cortices in presence of fearful stimuli. The present experiment was designed to test whether the amygdala, a crucial neural site in fear perception, might contribute to this effect. Six epileptic patients (mean age: 20 years) with lesions to the amygdala due to temporal lobe resection received tactile stimuli near the perceptual threshold, either on their right, left or both cheeks. Concurrently, they watched several blocks of movies depicting a face with a neutral, happy or fearful expression that was touched or just approached by human fingers. Participants were asked to distinguish between felt unilateral and bilateral tactile stimulation. Tactile perception was enhanced when viewing touch only towards a neutral face, while no effect was found when patients viewed touch towards fearful or happy faces. Results of the present experiment suggest that the amygdala modulates the activity of the somatosensory cortices, playing a crucial role in mediating the fear-specific enhancement in the VRT effect.
Fear-specific modulation of tactile perception is disrupted after amygdala lesions
BERTINI, CATERINA;SCARPAZZA, CRISTINA;LADAVAS, ELISABETTA
2012
Abstract
The perception of tactile stimuli on the face is modulated when subjects concurrently observe a face being touched; this effect is termed “Visual Remapping of Touch”, or the VRT effect, and might represent a visually evoked somatosensory activity. VRT effect is modulated by specific key information processed in face-to-face interactions: facial emotional expression. Indeed, tactile perception in healthy subjects is enhanced when viewing touch towards a fearful face compared to viewing touch towards neutral, happy or angry expressions. The fear-specific modulation of the VRT effect might be interpreted as an adaptive preferential enhancement of the somatosensory cortices in presence of fearful stimuli. The present experiment was designed to test whether the amygdala, a crucial neural site in fear perception, might contribute to this effect. Six epileptic patients (mean age: 20 years) with lesions to the amygdala due to temporal lobe resection received tactile stimuli near the perceptual threshold, either on their right, left or both cheeks. Concurrently, they watched several blocks of movies depicting a face with a neutral, happy or fearful expression that was touched or just approached by human fingers. Participants were asked to distinguish between felt unilateral and bilateral tactile stimulation. Tactile perception was enhanced when viewing touch only towards a neutral face, while no effect was found when patients viewed touch towards fearful or happy faces. Results of the present experiment suggest that the amygdala modulates the activity of the somatosensory cortices, playing a crucial role in mediating the fear-specific enhancement in the VRT effect.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
