The etiology of schizophrenia and the origin of language: overview of a theory.
Schizophrenia is present in all human populations with approximately the same incidence. Why does such illness persist given that it is associated with a reproductive disadvantage? What is the balancing advantage? A possible explanation is linked to human language. According to this hypothesis schizophrenia occurs as a manifestation of genetic diversity associated with language--the function by which Homo sapiens has separated from other primate species. Language originated by a genetic mutation that allowed the cerebral hemispheres to develop with a degree of specialization (or lateralization) reflected in cerebral asymmetries. Individuals with schizophrenia show lesser structural and functional brain asymmetries than the population as a whole, and this finding can be interpreted as a delay, or failure in, establishing hemispheric dominance for language. We review recent evidence supporting this theory.
Berlim
Marcelo T
MT
Schizophrenia Research Group, Department of Psychiatry and Forensic Medicine, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil.
Mattevi
Betina S
BS
Belmonte-de-Abreu
Paulo
P
Crow
Timothy J
TJ
D001921:Brain / Q000503:physiopathology; D002891:Chromosomes, Human, Pair 21 / Q000235:genetics; D041321:Chromosomes, Human, X / Q000235:genetics; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D015994:Incidence; D007802:Language; D017354:Point Mutation / Q000235:genetics; D011582:Psychological Theory; D012559:Schizophrenia / Q000209:etiology* / Q000235:genetics / Q000503:physiopathology