Cognitive impairment in schizophrenia is the core of the disorder

Patients with schizophrenia exhibit an exceedingly wide range of symptoms f rom a variety of domains. The cardinal features are abnormal ideas (such as delusions); abnormal perceptions (such as hallucinations); formal thought disorder (as evidenced by disorganized speech); motor, volitional, and beha vioral disorders; and emotional disorders (such as affective flattening or inappropriateness). In addition to these diverse, and sometimes bizarre sym ptoms, it has become increasingly apparent that the disorder is, to variabl e degrees, accompanied by a broad spectrum of cognitive impairments. This r eview addresses the question of whether the cognitive deficits seen in schi zophrenic patients are the core features of the disorder. In other words, w e explore whether schizophrenia is best characterized by symptoms or cognit ive deficits (we suggest the latter) and moreover, whether there is a speci fic cognitive deficit profile that may assist in diagnosis. First, we discu ss what the cognitive deficits are. Then we address in turn the reality, fr equency, predictive validity, specificity, course and susceptibility to neu roleptic effects of these cognitive impairments. In brief, we argue that va rious cognitive deficits are enduring features of the schizophrenia illness , that they are not state-related and are not specific to subtypes of the i llness, and, more specifically, that working memory and attention are chara cteristically impaired in patients with schizophrenia, irrespective of thei r level of intelligence. Last, we conclude that problems in these cognitive domains are at the very core of the dysfunction in this disease.