Is schizophrenia “the price that Homo sapiens pays for language”? Subcortical language processing as the missing link between evolution and language disorder in psychosis – A neurolinguistic approach

ObjectiveTo achieve a unified and plausible concept of the aetiology of psychosis.BackgroundFrom an evolutionary point of view, the capacity for language evolved relatively abruptly 150,000–200,000 years ago as a result of a saltational genetic change that allowed the two hemispheres to develop with a degree of independence. According to Crow (1997) the predisposition to schizophrenia might be a component of Homo sapiens-specific variation associated with the capacity for language. Crow (2000) suggested that schizophrenia is “the price that Homo sapiens pays for language”. Language impairment is one of the, core phenomenological characteristics of patients with schizophrenia (DeLisi, 2001). These symptoms might be understood as a breakdown of bi-hemispheric coordination of language. After reviewing the literature and regarding our own data concerning subcortical ambiguity processing, we suggest that subcortical language processing might play a crucial role as a missing link between the evolution of language (genetics), hemispheric dysbalance and language disorder in schizophrenia. Concentrating on the long time underestimated subcortical role of high order language function might open new perspectives in understanding the aetiology of psychosis.ConclusionFrom our point of view there might be at least two pathways useful in forming a neurolinguistic approach to understand language symptoms in schizophrenia: first, hemispheric imbalance might play a crucial role in the development of schizophrenia. The second pathway leads to a potentially disturbed interdependency between fronto-temporo-parietal and subcortical neural networks and their importance in the processing of high order linguistic functions (such as decoding ambiguities).