NEUROPSYCHOLOGICAL AND OLFACTORY DYSFUNCTION IN SCHIZOPHRENIA - RELATIONSHIP OF FRONTAL SYNDROMES TO SYNDROMES OF SCHIZOPHRENIA

Behavioural changes and cognitive impairments in schizophrenia have be en linked to disturbances of complex neural networks involving both fr ontal and subcortical systems. Current literature has emphasised the r ole of the dorso-lateral prefrontal cortex (DLPFC) and its connections with hippocampus in the pathogenesis of schizophrenia. Based on a rev iew of the literature, this paper examines other possible prefrontal a reas that contribute to the manifestations of schizophrenia. We focus on the orbito-frontal cortex (OFC) and argue that it also plays an imp ortant role in the behavioural manifestations, symptoms and cognitive impairments observed in schizophrenia. The importance of fronto-striat o-thalamic circuits connecting these prefrontal sites with subcortical structures is examined and the relevance of functions specific to the se circuits or their components are briefly discussed. The subdivision of the functions of the prefrontal cortex into 'prefrontal' syndromes are examined and related to both the behavioural and symptom-based sy ndromes of schizophrenia. Possible dissociations of function of the va rious prefrontal syndromes and the relationship of these to schizophre nia syndromes may provide dues to the underlying neurobiology of schiz ophrenia. The use of tasks deemed specific to DLPFC and OFC networks m ay be useful as probes to examine the integrity of these circuits. We discuss such 'circuit-specific' tasks including delayed response, dela yed alternation and object alternation tasks derived from the animal l iterature and other tasks such as olfactory identification ability. Th is approach raises the possibility that a number of prefrontal cortica l areas and their subcortical connections are important in accounting for the heterogeneity of schizophrenia.