"The body is ubiquitous in perceptual experience and is central to our sense of self and personal identity. Disordered body representations are central to several serious psychiatric and neurological disorders. Thus, identifying factors which contribute to the formation and maintenance of body representations is crucial for understanding how body representation goes awry in disease, and how it might be corrected by potential novel therapeutic interventions. Several types of sensory signals provide information about the body, making the body the multisensory object, par excellence. Little is known, however, about how information from somatosensation and from vision is integrated to construct the rich body representations we all experience. This project fills this gap in current understanding by determining how the brain builds body representations (BODYBUILDING). A hierarchical model of body representation is proposed, providing a novel theoretical framework for understanding the diversity of body representations and how they interact. The key motivating hypothesis is that body representation is determined by the dialectic between two major cognitive processes. First, from the bottom-up, somatosensation represents the body surface as a mosaic of discrete receptive fields, which become progressively agglomerated into larger and larger units of organisation, a process I call fusion. Second, from the top-down, vision starts out depicting the body as an undifferentiated whole, which is progressively broken into smaller parts, a process I call segmentation. Thus, body representation operates from the bottom-up as a process of fusion of primitive elements into larger complexes, as well as from the top-down as a process of segmentation of an initially undifferentiated whole into more basic parts. This project uses a combination of psychophysical, electrophysiological, and neuroimaging methods to provide fundamental insight into how we come to represent our body."