# Augmentation of frontoparietal gamma-band phase coupling enhances human altruistic behavior

## TL;DR

This study shows that enhancing brain synchronization in specific regions with non-invasive stimulation increases altruistic behavior in humans.

## Contribution

The study provides causal evidence linking frontoparietal gamma-band phase coupling to altruism using neurostimulation.

## Key findings

- Transcranial alternating current stimulation enhances frontoparietal gamma-band coherence.
- Enhanced coherence increases altruistic behavior during disadvantageous inequality.
- Computational modeling shows increased weight on other-regarding concerns after stimulation.

## Abstract

Cooperation, productivity, and cohesion in human societies depend on altruism, the tendency to share resources with others even though this is costly. While altruism is a widely shared social norm, people vary strongly in their inclination to behave altruistically, in particular across situations with different types of inequality in resource distribution. What neurobiological factors underlie this variability? And can these be targeted by interventions to enhance altruistic behavior? Here, we build on electroencephalography (EEG) evidence that altruistic choices during disadvantageous inequality correlate with oscillatory gamma-band coherence between frontal regions (representing other’s interest) and parietal regions (representing neural evidence accumulation). We apply a transcranial alternating current stimulation protocol designed to exogenously enhance this fronto-parietal coherence and find that this leads to increased altruism, specifically during disadvantageous inequality as hypothesized based on the EEG findings. Computational modeling reveals that this transcranial entrainment does not just add noise to the decision process but specifically increases the weight individuals assign to other-regarding concerns during choices. Our findings show that altruism can be enhanced by neurostimulation designed to enhance oscillatory synchronization between frontal and parietal areas. This establishes a neural basis for altruism and identifies a neural target for interventions aimed at improving prosocial behavior.

Prior work from this group showed that some types of altruistic choices were related to the coherence of gamma-band neural oscillations between frontal and parietal brain regions. This study in humans provides causal evidence for the relationship using non-invasive brain stimulation, expanding our understanding of the neural basis for altruism.