Altruistic behaviors such as a helping may have a crucial role in stabilizing the survival of our species and social relationships. Spontaneous helping behavior is observed in humans, even in the early stages of development; however, it is rarely observed in other species. On account of the evolutionary background, our brain would be expected to have specific mechanisms underlying these behaviors. A considerable number of studies have tackled this issue by using noninvasive neuroimaging techniques such as functional magnetic resonance imaging (fMRI). In this paper, I review studies that have revealed the neural mechanisms underlying the motivation of helping others, as well as mentalizing functions. I also introduce the basic procedures of psychological experiments using fMRI. In the final part, I discuss advanced issues about the negative aspects of altruism such as excessive punishment or revenge to an unfaithful other and self-sacrifice.
