The neuropsychology of schizophrenic speech.

Recent interest in the biological basis of schizophrenia has led to a reexamination of many symptomatic aspects of the disorder in terms of brain-behavioral models. Schizophrenic speech disturbances have traditionally been described in terms of a model of acquired aphasia. We review some of the limitations of this model and provide an alternative model for the study of some characteristics of schizophrenic speech based on neuropsychological theories of frontal lobe dysfunction in schizophrenia. The emphasis is placed on the study of productive errors noted in schizophrenic speech, most notably verbal perseverations. In a study of errors observed during a sample of 15 schizophrenics performance on a confrontation naming test, we were able to reliably identify and classify hierarchic categories of verbal perseverations occurring at both semantic and phonemic levels. These perseverations constituted 20% of the total errors. We argue that these perseverations represent a special case of executive dysfunction resulting from a disturbance of language monitoring mechanisms. We examine the implications of these findings for a hypothesis of schizophrenic speech disturbances in terms of frontal lobe dysfunction and the developmental neuropathological processes involved in the illness.