We aim to understand how our brain and body contribute to the experience of a “self”. A basic perception of ourselves as entities is that of being and having a body. Phenomenologically these experiences occur often in interaction with others and our surroundings. We use functional magnetic resonance imaging (fMRI) of the brain and the spinal cord, functional near infrared spectroscopy (fNIRS), behavioral measures and psychophysics to understand how humans differentiate between “self” and “other” – and what happens if this differentiation is altered. We study dysfunctional self-other-differentiation in psychiatric conditions like schizophrenia and in states of altered self-perception that can be evoked pharmacologically or with body illusions.