Neurocognitive changes and negative symptoms in schizophrenia

It is widely recognized that schizophrenic disorders are often associated with impairments of cognitive performance. More recently, disorders of higher cognitive control processes ("executive control functions") have captured the attention of researchers as they can considerably impair patients' abilities to live an independent life. Apart from that, considering the heterogeneity of schizophrenia, there have been attempts to relate psychopathological syndromes to changes in distinct cognitive domains. The present review selectively focuses on evidence associating negative symptoms in schizophrenia with deficient performance in specific executive domains. Neurobiological evidence points to biochemical, structural and functional abnormities in the frontal cortex and associated fronto-subcortical circuits as a common basis of both schizophrenic negative symptoms and disorders of executive control. In a multitude of neuropsychological studies, an association between negative symptoms and problems in the domains of response inhibition, multitasking, cognitive flexibility, contextual updating, problem solving and verbal fluency has been reported. In some cases, however, the disorganization syndrome but not the negative syndrome has been linked with impaired behaviour in these domains. The inconsistencies might be partly due to the unsatisfactory differentiation between the two symptom complexes. Future research should furthermore consider a more precise differentiation between primary and secondary negative symptoms. Finally, the assessment of executive control functions should be both specific and ecologically valid.