Executive dysfunctions in schizophrenia

Abstract. Studies suggest that executive functions inpatients with schizophrenia are markedly impaired ascompared with normal controls. Most previous studiesemployed tests of executive functions adopted fromfrontal lobe neuropsychological paradigms based on lesionstudies. This study employed several more recentlydeveloped theory–driven tests of executive functions addressingthe construct of the supervisory attentionalsystem. We explore the pattern of executive function impairmentusing factor analysis and subsequently investigatethe relationships between these executive functionfactors and the clinical features in a sample ofchronic schizophrenic patients. A total of 51 patientswith chronic schizophrenia were recruited. The SustainedAttention Response to Task (SART), Six ElementsTest (SET) and Hayling Sentence Completion Test (HSC)were used to assess executive functions. Three factorswere identified within the executive function tests: 1)The semantic inhibition factor comprised items in theHSC, 2) the action/attention inhibition factor comprisedthe SART commission error and the SET rulebreakingscore and 3) the output generation factorcomprised the SET raw score and the correct SART response.Significant relationships were found betweenthese derived factors and clinical features after partiallingout the confounding effect of age, education andillness duration. The three theory–based tests of executivefunction were shown to have good construct validityamong the group of chronic schizophrenic patients.Part of the findings were presented at the 11^th Biennial Winter Workshopon Schizophrenia at Davos, Switzerland, 24 February–1 March 2002