In brains of patients with schizophrenic and affective disorders pathomorphological changes have been shown focussing in frontal and temporal cortex. The volume reduction in prefrontal cortex of schizophrenic patients is hypothesized to be based on a reduction of neuropil. A decrease of synaptic proteins and a decrease of dendritic spines of pyramidal cells can additionally be the origin of disconnections of neurons. Affection of the glutamatergic, GABA-ergic and dopaminergic system and reduction of interneurons could be the correlate of a deficient neuronal network which might be combined with exogen factors generate psychotic symptoms. Reelin and associated proteins are candidate molecules. Their dysregulation might explain essential features of the dysfunctional network of schizophrenia.