Summary: New research clarifies how the somatosensory cortex contributes to prosocial behavior.
Source: Netherlands Institute for Neuroscience, KNAW.
Helping people in need is a cornerstone of human society. It is often assumed we help because we empathically share others’ pain. Neuroscience has shown that when we see someone in pain, brain regions involved in touch and emotion become active as if we were experiencing the pain ourselves. A study led by Selene Gallo tested whether changing activity in those tactile brain regions while people watched another person in pain would change their willingness to help. The findings, published in eLife on 8 May 2018, shed light on the neural basis of social behavior and may guide treatments for conditions in which these mechanisms are impaired.
Researchers at the Social Brain Lab, led by Valeria Gazzola and Christian Keysers at the Netherlands Institute for Neuroscience (KNAW), designed an experiment in which participants observed a person receiving a swat on the hand and could choose to reduce that person’s pain by donating money. Donations came at a personal cost: money given to reduce the victim’s pain was money the participant could not keep. While participants watched and made decisions, the researchers recorded and manipulated activity in tactile brain regions.
Using electroencephalography (EEG), the team measured participants’ brain activity while they decided how much to donate. EEG signals from tactile cortex regions, specifically the somatosensory representation of the hand, rose on trials when participants chose to give more. To test causality, the researchers then used brain stimulation to alter activity in those somatosensory areas. Under normal conditions participants gave more money when the observed pain was greater. But when tactile cortex activity was disrupted, two related effects emerged: participants were less accurate at judging how much pain the other person was in, and they stopped adjusting their donations appropriately to match the victim’s level of pain.
An important social role for the somatosensory cortex
These results suggest that brain regions evolved to perceive touch and pain on our own bodies also serve a social function. The somatosensory cortex helps translate visual information about another person’s bodily harm into a precise internal sense of how much pain the victim is experiencing. That internally generated perception of the other’s pain appears necessary for making well-calibrated prosocial decisions—deciding when and how much to help.
Linking vicarious somatosensory activation to helping behavior advances our understanding of the neural mechanisms behind empathy and prosocial choices. The findings have potential relevance for developing pharmacological or behavioral interventions for disorders characterized by impaired empathy or reduced prosocial responding, such as psychopathy or callous-unemotional traits in children.
Source: Selene Gallo – Netherlands Institute for Neuroscience, KNAW
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Original research: Abstract for “The causal role of the somatosensory cortex in prosocial behaviour” by Selene Gallo et al., published in eLife on 8 May 2018. DOI: 10.7554/eLife.32740
Netherlands Institute for Neuroscience, KNAW. “The Neuroscience of Prosocial Behavior.” NeuroscienceNews. 25 May 2018.
Abstract
The causal role of the somatosensory cortex in prosocial behaviour
Observing another person’s suffering activates brain areas also involved when we ourselves feel pain. Whether such vicarious activity shapes helping behavior has been unclear. In this study, participants watched a confederate show pain either through a hand reaction after a swat or through facial expressions, and could reduce that pain by donating money. Participants tended to donate more money when the confederate showed stronger pain. EEG recordings showed that activity in the primary somatosensory cortex (SI) representing the hand correlated with donation amounts. Transcranial magnetic stimulation (TMS) that altered SI activity disrupted the link between perceived pain and donation—but only when pain was conveyed via the hand. High-definition transcranial direct current stimulation (HD-tDCS) altering SI activity also impaired participants’ perception of another’s pain. Together, these experiments indicate vicarious somatosensory activations contribute to prosocial decision-making by enabling accurate perception of another person’s bodily pain, a perception that guides helping behavior.