The role of mental symptomatology is to describe various clinical symptoms without referring to their pathogenesis. This may be because of the influence of K. Jasper's General Psychopathology.
 However, from the mid-19th to early 20th century, when modern psychiatry was established, some excellent hypotheses concerning the pathogenesis of mental symptoms were proposed, although it was difficult to verify these hypotheses because of technical limitations. The purpose of this article was to review the historical development of symptomatology in psychosis with reference to the pathogenesis. W. Griesinger (1845, 1861) distinguished between the etiology and pathogenesis of a disease, and stated that every mental disease is a manifestation of brain disease. Subsequent investigators elaborated on this view: C. Wernicke (1894, 1906) proposed the disconnection of the association tracts, and P. Flechsig (1894, 1920) regarded the late myelinating "association areas'" (this term was from Flechsig) as the field of the mind. J. H. Jackson (1895) proposed the evolutionary and hierarchical organization of the nervous system. E. Kraepelin (1913) speculated on the hypoactivity of the frontal cortex-the highest cerebral centers according to Jackson's terminology-and hyperactivity of the temporal speech cortex as the pathogenesis of psychotic symptoms in dementia praecox, which were found to be the case based on neuroimaging methods over sixty years later. Currently, the pathogenesis of mental symptoms is being investigated from the viewpoint of the dysfunctions of neural circuits, such as cortico-limbic, cortico-thalamic, or cortico-striatal circuitry.
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