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Title: The cerebral lateralisation of somatosensation in schizophrenia
Author: White, Thomas P.
ISNI:       0000 0001 3567 1398
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2007
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The lateralisation of sensory processing provides a measure of efficiency of information processing in the human brain. Several event-related potential (ERP) studies have suggested that the lateralisation of somatosensory processing is disturbed in schizophrenia, with individuals with the disorder exhibiting a symmetrical response over both parietal cortices in contrast to the contralaterally dominant response observable in healthy adults (Jones and Miller, 1981; Cooper et ai., 1985; Andrews et al., 1986). This finding has, however, been disputed by several other studies (Shagass et al., 1983; Furlong et ai., 1990; Allen et ai., 1991). Recent changes in ERP acquisition and analysis procedures, coupled with the emergence of functional magnetic resonance imaging (fMRI), dictate further investigation of this phenomenon. 24 right-handed medicated individuals with schizophrenia, 23 right-handed healthy individuals and 10 non-right-handed healthy individuals were recruited for an ERP study, which used a piezoelectric device attached to the index finger to elicit a passive somatosensory response. Little evidence of abnormallateralisation of somatosensory processing at PI, N1 and P3 latencies was found in individuals with schizophrenia, despite several amplitude reductions in these ERP components. The same sample also took part in an extended experiment modified for fMRI. In this study the schizophrenia group exhibited significantly diminished lateralisation of the primary somatosensory cortex (SI) response when compared to the healthy right-handed group (p=0.029) and a borderline reduction when compared to the healthy non-right-handed group (p=0.059). Furthermore, the contralateral SI response was shown to be significantly less focal in the schizophrenia group when compared to both healthy groups. Symptom analysis showed that high scores in the disorganisation syndrome were associated with loss of SI focalisation, in accord with Spitzer's cortical spreading hypothesis of disorganisation (Spitzer et ai., 1993; Spitzer et al., 1994; Spitzer, 1997). Given the disturbances observed in inter-hemispheric lateralisation and intra-hemispheric focalisation, it is likely that there is a generalised problem of cortical recruitment in schizophrenia. Anterior cingulate cortex (ACe) activity was compared between the study groups in light of the proposed roles of ACC in cortical recruitment and cerebral coordination. Our findings of reduced ACC activity in the schizophrenia group provide some support for the hypothesis that ACC dysfunction underlies the disturbances of lateralisation and focalisation reported in schizophrenia.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available