The neurophysiological correlates of altruism: A scoping review of fMRI, EEG, and autonomic studies

Altruistic motivation, a fundamental aspect of human behavior, commands significant neuroscience attention. This scoping review, following PRISMA-ScR guidelines, synthesizes findings from 45 fMRI, EEG, fNIRS, and autonomic nervous system (ANS) studies published between 1975 and 2024, exploring the neural basis of costly, other-oriented altruism. Our review covers experimental paradigms utilizing fMRI, EEG, and autonomic measures to interrogate neural and physiological responses associated with altruistic decision making and behavior. Importantly, inclusion was not limited to online, state-dependent, or event-related measurements; studies employing various acquisition timings were encompassed, as long as they examined neural or physiological correlates of altruistic motivation. fMRI studies consistently reveal engagement of a complex neural network, including medial and dorsolateral prefrontal cortex, temporoparietal junction, insula, and anterior cingulate cortex, integrating social cognition, value-based decision making, and emotional processing inherent in altruistic acts. EEG research highlights increased left frontal activity, indicative of approach-oriented motivation, and frontal midline theta, reflecting cognitive control during altruistic choices. ANS findings exhibit variability but tentatively suggest parasympathetic dominance in altruistic context. A key contribution is a multi-stage information-processing model of altruistic motivation, integrating these modalities from socio-affective appraisal through value computation, motivational orientation, and cognitive control to behavioral implementation. Findings elucidate the interplay of cognitive and emotional processes driving altruism, offering a nuanced conceptual framework. Future research, including longitudinal studies, cross-cultural comparisons, and ecologically valid assessments, is vital for advancing theoretical and practical understanding of the neurophysiology of altruism.