Introduction
The concept of a soul or vital force is consistent across scientific, medical, theological, and philosophical thought1 . The soul is often described as contained within specific organs but separate from the body, and it is unsurprising that its location has been a subject of great debate throughout history2 . Despite much contention, those historically in search of the soul have generally agreed that it is the essence of a person – their true and immortal self1,3 . Indeed, when confronted with the challenge of identifying themselves, most people point to their chest or, approximately, their heart. This cardiocentric model of who we are is described in humanity’s earliest writings from the third millennium BCE, indicating that Ancient Egyptians believed souls were immortal and located within the hearts of impermanent bodies4 . The related idea of the pneuma – ancient Greek for breath, spirit, or soul – represents one among many similar beliefs about the essence of human life5 . Consistent with the heart’s exalted status throughout history6 , and until very recently, irreversible cardiac arrest was considered the medical standard for death7-9 . Which is to say, when your heart stopped beating, you stopped being. However, the importance of other bodily organs did not go unnoticed by our ancestors. Notable philosophers such as Plato and Descartes championed the brain as the locus of the soul10-13 and modern definitions of death rest squarely on the structural and functional integrity of the brain, not the heart7,8 .