Most neurological diseases are multifactorial diseases, where environmental conditions combine with genetic background or somatic mutations to trigger a pathological state. In the case of Parkinson's Disease and Schizophrenia, recent research revealed that susceptibility genes coded for proteins involved at different steps of specific metabolic networks and cellular processes. Comprehension of the pathology of those diseases is therefore very likely to benefit from Systems approaches. This is also true of their symptomatology, affecting neurological systems at molecular, cellular, and microcircuit levels.