Bottom-up and top-down processes in body representation

Understanding the mechanisms through which the brain represents the body is one of the most challenging issues in neuroscience. Our body is, in fact, a special subject of investigation given its several interacting systems: touch, vision, proprioception, motor behavior, semantic comprehension, emotions etc. We continuously receive top-down and bottom-up information about our own body. These inputs interact to form body representations. Although many studies have attempted to fractionate body representation into different cognitive components (Berlucchi & Aglioti, 2010; deVignemont et al. 2010), as well as to identify their neural correlates, a universally accepted taxonomy (Medina & Coslett, 2010; Longo et al., 2010) is far to be achieved. This dissertation aims to present a series of studies assessing body representation, from both a bottom-up and top-down perspective. These studies mainly focus on 1) summarizing fMRI data from previous studies and exploring the possibility of a neural segregation between different body representations. Results from the first study provide a neural framework within which to investigate how lack of sensorimotor information – following from loss of bottom-up information (i.e. amputation) – changes body representation from both a 2) structural and 3) functional point of view. As regards the top-down perspective, the studies presented aimed at 4) investigating the presence of body representation deficits in brain-damaged patients and, in particular, in those affected by personal neglect and 5) identifying the neural underpinnings of body representation in post-stroke patients. The first introductive chapter will provide a general overview of the current definition, classification and neural substrates of body representation. Each following chapter will then provide a more focused introduction about the specific issues investigated in the above-listed experimental studies.