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Title: Imaging the structure and function of limbic and subcortical regions in depression
Author: Shah, Premal Jitendra
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2000
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The striatum, being part of the limbic system, shows changes during depression in both structural and functional imaging studies, suggesting the involvement of dopamine. Using IBZM, a SPET ligand with high dopamine D2/3 receptor selectivity, in-vivo striatal D2/3 receptor availability was examined in 15 depressed in-patients and 15 matched controls. Depressed patients had increased receptor availability, implying reduced striatal dopaminergic activity in depressed patients. Increased receptor availability was related to objective measures of psychomotor retardation in the depressed group. Inter-individual IBZM binding variability may be due to a combination of state and trait effects. Two trait effects were found in controls-sexual dimorphism, independent of affective illness, with women showing higher availability, and a large effect related to temperament or personality, confirming the functional complexity of the striatum. Evidence for structural change in depression is conflicting, the strongest being for striatal and frontal lobe atrophy in unipolar depression. Patients with chronic treatment resistant unipolar depression (CTRD) were examined, as they may be expected to have the greatest likelihood of exhibiting structural change. Voxel based analysis and conventional volumetry were used to compare the high resolution MRI images of twenty patients with CTRD, with 20 matched recovered patients and 20 matched healthy controls. Only CTRD patients exhibited MRI differences. Both VBA and conventional volumetry revealed frontal lobe and right striatal atrophy. Additionally, VBA revealed reduced grey matter density in left temporal lobe and bilateral anterior hippocampi, particularly the left. Neocortical changes correlated with the cumulative illness severity. Medial frontal grey matter reductions correlated with age, psychomotor retardation as well as current and past illness severity in patients groups. Left hippocampal grey matter reductions correlated with reduced episodic verbal memory. VBA is, therefore, a sensitive, valid and complete analysis of MRIs providing results consistent with contemporary hypotheses.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (M.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available