Even a cursory review makes it clear that the operation of the brain critically depends on a complex interaction of spatially segregated neural systems. An adequate description of these interactions and an understanding of their nature are therefore an important challenge for neuroscience. While this applies to normal and abnormal brain functions, a study of the nature of corticocortical interactions will be needed most of all in the study of diseases and conditions in which an alteration of connectivity is assumed to play a prominent role. A case in point is schizophrenia, in which convergent evidence from neuroanatomical, neurophysiological, pharmacological and theoretical studies suggests that a disturbance of cortical connections may play an important role in producing a functionally devastating and characteristic syndrome based on a pathology that is (comparatively) subtle and possibly diffuse [17, 22, 43, 70].