Schizophrenia is a complex illness of the human being. That is one of the illness of behavior with biological origin, not without psycho-social contributions. The complexity comes from a several face what could show this illness, with positive symptoms, or negative symptoms or, like most of the time, both. In definitions the positive symptoms are the presents of perceptual disorders, like different kind of hallucinations, delusions, and the negative symptoms are the absences of motivations, volitions, feelings. Most of the studies show that the principal cause of this illness is the low presence of dopamin in synapsis of the mesocortical tracts, which comes from the ventral tegmentum of thalamus, with relations of nucleus nigra. That cause the low function of frontal cortex, wich cause the negativ symptoms, and in same time the higher dopamin concentration in synapsis of the mesolimbical tracts, which cause the positive symptoms.