We will separate two notions generally confounded in the literature: anatomical and functional connectivity. The rationale for this is that we suppose the latter to be related to the common pathophysiological pathway leading to the clinical expression of the disease. The anatomical aspect is assumed to be one of the possible causes for the dysfunction. We will also discuss two levels of connectivity: a local level, mainly concerning the direct surroundings of the neurons in the gray matter, and a longrange level, mainly concerning the white fiber tracts connecting distant parts of the brain. A third anomaly of connectivity could be related to neurons connecting with erroneous targets.
