Cortical inhibitory deficit as a core feature of schizophrenia: electrophysiological and neurocognitive studies

Shahrzad Mazhari

    Research output: ThesisDoctoral Thesis

    135 Downloads (Pure)

    Abstract

    Schizophrenia (SZ) is a complex and likely heterogeneous disorder characterised by considerable variation in clinical symptomatology and cognitive functioning. In the Western Australian Family Study of Schizophrenia (WAFSS), two major subtypes were identified, one exhibiting pervasive, generalised cognitive deficit (CD), and another with only mild or focal cognitive deficits (cognitively spared, CS). Linkage analysis demonstrated that the two subtypes were genetically distinct (Hallmayer et al., 2005). The aim of the research reported in the current thesis was to test the hypothesis that cortical inhibition (CI) deficit is a core feature of the CD subtype. This hypothesis was tested by examining the performance of patients in three functional domains related to CI: neuromotor eye movement control, electrophysiological eventrelated potentials, and visuospatial working memory. Archival data from the WAFSS were used to compare the performance of 93 schizophrenia patients (CD = 47, CS = 46), 99 unaffected relatives and 62 healthy controls on a standard antisaccade task. A new sample of 57 patients with schizophrenia (CD = 28, CS = 29) and 50 healthy controls were also assessed on: i) the two additional antisaccade paradigms (overlap and delayed); ii) P50, N100, and P200 mid-latency auditory gating measures; and iii) a visuospatial working memory test. The results showed that schizophrenia patients, and particularly those classified as CD, were impaired in all three domains: (i) on the antisaccade tasks, CD patients demonstrated deficient response inhibition and response generation; (ii) in mid-latency sensory gating, CD patients showed attenuated responses to the first click of N100 and P200 components; and (iii) on the VSWM test, they exhibited impairments in the maintenance of direction of spatial location, as well as deficient use of a vertical frame of reference to support visual information processing. The results of these investigations indicate consistently poor performance of CD patients on separate measures of CI functioning, and support the notion of CI deficit as a prominent feature of CD patients when compared to CS patients.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2010

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