Information received by the human cortex is supplied by two main sources: extrinsic stimuli delivered by the external environment and intrinsic information regarding the body and self. We reanalyzed electrophysiological data involving the same external stimuli, but manipulating the degree of ‘self-projection’ to locations inside and outside the body border. Electrical neuroimaging and spatial principal component analysis (PCA) showed a bipartition of the cerebral cortex into two main subsystems: occipital and frontal activity was similar across tasks; activity in temporo-parietal and anterior frontal regions was modulated according to the manipulation of self-projection in a given task. These data suggest that the first system relates to external stimulus processing (‘extrinsic’) and the latter one relates to processing of the ‘internal milieu’ of body and self (‘intrinsic’).
