Biomedical subjects

T Toulopoulou

Publications and source records attributed to T Toulopoulou.

2 recordsLinked to original sources

PubMed2005

Brain MRI abnormalities in schizophrenia: same genes or same environment?

BACKGROUND: Structural brain volume abnormalities are among the most extensively studied endophenotypes in schizophrenia. Bivariate genetic model fitting (adjusted to account for selection) was used to quantify the genetic relationship between schizophrenia and brain volumes and to estimate the heritability of these volumes. METHOD: We demonstrated by simulation that the adjusted genetic model produced unbiased estimates for endophenotype heritability and the genetic and environmental correlations. The model was applied to brain volumes (whole brain, hippocampus, third and lateral ventricles) in a sample of 14 monozygotic (MZ) twin pairs concordant for schizophrenia, 10 MZ discordant pairs, 17 MZ control pairs, 22 discordant sibling pairs, three concordant sibling pairs, and 114 healthy control subjects. RESULTS: Whole brain showed a substantial heritability (88%) and lateral ventricles substantial common environmental effects (67%). Whole brain showed a significant genetic correlation with schizophrenia, whereas lateral ventricles showed a significant individual specific correlation with schizophrenia. There were significant familial effects for hippocampus and third ventricle, but the analyses could not resolve whether these were genetic or environmental in origin (around 30%each). CONCLUSIONS: Using genetic model fitting on twin and sibling data we have demonstrated differential sources of covariation between schizophrenia and brain volumes, genetic in the case of whole brain volume and individual specific environment in the case of lateral ventricles.

Adolescent↗

PubMed2003

Episodic memory in schizophrenic patients and their relatives.

BACKGROUND: Memory dysfunction among healthy relatives of patients with schizophrenia suggests that genetic liability to the disorder can also be manifested as cognitive impairment. This study was designed to further elucidate the nature of the memory dysfunction being transmitted. METHOD: Memory function was assessed in 62 schizophrenic patients, 98 of their healthy relatives and 66 controls. Material-specific immediate/delayed recall and percentage retention were investigated using the Logical Memory and Visual Reproduction tests of the Wechsler Memory Scale (WMS). A third subtest of the WMS, the Associate Learning and a visual analogue of it, the Abstract Paired Associates, were used to measure verbal and visual learning. Current general intellectual function was assessed using a five-subtest short-form of the Wechsler Adult Intelligence scale-Revised (WAIS-R). RESULTS: Schizophrenic patients performed significantly worse than controls on nearly all measures. Their relatives also showed significant deficit on the immediate and delayed recall of the Logical Memory, immediate recall of the Visual Reproduction, and the Abstract Paired Associates tests. Logical memory was substantially more impaired than the other measures for both patients and relatives. The deficit in immediate recall of the Logical Memory remained significant even after excluding those relatives with an Axis I diagnosis and schizotypal personality disorder. These findings were despite the relatives having an equivalent level of general intellectual function to that of controls. CONCLUSION: Familial, presumed genetic, liability to schizophrenia may be expressed as dysfunction in verbal memory.

Adolescent↗