What do (or don't) we see with MRI?

The understanding of our brain is a major scientific challenge of the 21th century. In addition to scientific aims, elucidating the biological mechanisms underlying our mental life, the goals are mainly to understand and essentially prevent and cure the disorders of brain function, the neurological and psychiatric illnesses, in aging populations, and beyond to repair or even replicate brain function. Neuroimaging, especially MRI (Magnetic Resonance Imaging) has become an inescapable approach toward this quest as neuroimaging allows to investigate non invasively and in situ, in healthy or diseased humans, the relationship between brain structure and function. Fine brain anatomy and brain connections can be observed in 3 dimensions, and networks involved in whatever cognitive processes become visible. Still, those imaging methods have limits, first from their physical principles, but mainly from the ways results are obtained and exploited.  It is tempting to rely on those beautify images to feed the “neo fields” which are neuro-economics, neuro-education, neuro-marketing, neuro-ethics or even neuro-politics, but modesty must prevail to avoid any hasty overinterpretation of those images. The object of this short article is to illustrate, from a few examples, the potential and limits of neuroimaging, especially MRI, to explore the human brain.