A scientific revolution is foreseen in the coming decades in MindBrain Science: will a sensorium be found? In the 19th century, the term "sensorium" denoted the hypothetical part of the brain which immediately underlies a subjective perceptual state. Such immediate correlate of consciousness has always been actively pursued by neuroscientists, with opinions ranging from localized cortical or subcortical areas to holistic views. We examine psychophysical isomorphism, proposed in the 1930's by Wolfgang Köhler, and its idea that the structure of experience is identical to the structure of the underlying brain processes. One step further was taken by Edwin Boring, suggesting (but ultimately rejecting) that qualitative mental states are identical to physico-chemical qualities. We explore this view, to be called "qualitative physicalism" (or the colored-brain thesis), and which is at odds with the cognitive paradigm of the 1970's, which tends to deride such "Cartesian materialism" (as expressed by Dennett).