Does physical attractiveness of the face affect neural correlates of empathy for pain? A fNIRS study

Background: Brain areas involved with the direct experience of pain are also involved with the observation of pain in others. Indeed, a higher brain activation registered when observing individuals in painful versus non-painful condition is interpreted as an empathic reaction. However, empathy for pain is modulated also by other variables such as group membership or attractiveness. As shown by the so-called Racial Bias in Empathy (RBE), even simple information about group affiliation can influence brain empathic responses (Sessa, Meconi, Castelli, & Dell’Acqua, 2014). Previous research demonstrated that enhancing attention to others suffering, to individual attributes and including other-race individuals in one's own team may reduce the racial bias (Sheng & Han 2012). Thus, we aimed to assess cortical activity when attention is focused on an individual’s painful feelings as a cognitive strategy that enhances the individuated processing of persons. Methods: Brain activity, considered in its hemodynamic (optical imaging: functional Near-Infrared Spectroscopy, fNIRS) components (oxygenated [oxy-Hb] and deoxygenated hemoglobin [deoxy-Hb]) was monitored when 22 subjects (Mage=24.9; SD=3.6) observed faces (Attractive; Unattractive) that express painful conditions (Pain; No pain) and were asked to rate the attractiveness and pain feeling of the face. A total of 8 channels was considered to target Inferior Frontal Gyrus (IFG), sensory cortex and temporo-parietal junction (TPJ). In addition, the cortical lateralization effect (more left or right) was explored. Oxy-Hb and deoxy-Hb levels were analyzed for each channel, selected regions of interest and lateralization. Results: Single channel analyses revealed significant lower oxy-Hb levels in left IFG when asking participants to rate both face’s attractiveness and pain. In addition, single channel analyses revealed lower levels of deoxy-Hb in the left TPJ for attractive faces and in the right TPJ for unattractive faces, in both pain conditions. Instead, beyond attractiveness, higher deoxy-Hb values were found in the left hemisphere when subjects were asked to rate face pain. Conclusions: These fNIRS significant effects could be due to enhanced attention to faces physical features and revealed a right/left lateralization tendency that were both discussed at the light of emotional processing and empathic response. Future research in the field of empathy for pain may benefit from the integration of hemodynamic and electrophysiological measures as added value to investigate pro-social behavior, which is in line with social standards. References Sessa, P., Meconi, F., Castelli, L., & Dell’Acqua, R. (2013). Taking one’s time in feeling other-race pain: an event-related potential investigation on the time-course of cross-racial empathy. Social cognitive and affective neuroscience, 9(4), 454-463. Sheng, F., & Han, S. (2012). Manipulations of cognitive strategies and intergroup relationships reduce the racial bias in empathic neural responses. NeuroImage, 61(4), 786-797.