Comparative approaches to cortical microcircuits.

Recent trends in neuroscience have narrowed the scope of this field, notably through the progressive elimination of 'model systems' that were key to the development of modern molecular, developmental and functional neuroscience. Although the fantastic opportunities offered by modern molecular biology entirely justify the use of selected organisms (e.g., for their genetic advantages), we argue that a diversity of model systems is essential if we wish to identify the brain's computational principles. It is through comparisons that we can hope to separate mechanistic details (results of each organism's specific history) from functional principles, those that will hopefully one day lead to a theory of the brain.