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Biomedical subjects

J Brar

Publications and source records attributed to J Brar.

5 recordsLinked to original sources
PubMed1998

Functional hypofrontality and working memory dysfunction in schizophrenia.

OBJECTIVE: Hypofrontality is a common but not invariable finding in schizophrenia. Inconsistencies in the literature may reflect, in part, the fact that abnormal physiological responses in the prefrontal cortex are best identified under conditions that place well-specified functional demands on this region. METHOD: The authors studied eight patients with schizophrenia and eight matched comparison subjects using [(15)O]H2O positron emission tomography and the "N-back" task, which activates the prefrontal cortex as a function of working memory load in normal subjects. RESULTS: Under low-working-memory-load conditions, the accuracy of both groups in the N-back task was equal, but when the memory load increased, the patients' performance deteriorated more than did that of the comparison subjects. The regional cerebral blood flow response to increased working memory load was significantly reduced in the patients' right dorsolateral prefrontal cortex. CONCLUSIONS: These results confirm the importance of using tasks that tap specific cognitive functions, linked to specific neural systems, in studies of brain-behavior relationships in schizophrenia. Hypofrontality is reliably demonstrated in schizophrenia during tasks that engage working memory functions of the prefrontal cortex.

Functional Laterality↗
PubMed1997

PET brain mapping study of auditory verbal supraspan memory versus visual fixation in schizophrenia.

Changes in regional cerebral blood flow (rCBF), associated with performance of an auditory verbal supraspan memory task, were studied in eight remitted DSM-III-R schizophrenic patients and eight pair-wise matched normal controls. Four positron emission tomography (PET) scans, using the [15O]-H2O technique, were acquired: two while subjects fixated a cross hair and two while performing a verbal free-recall supraspan memory task. Task performance showed typical patterns of recency and primacy effects in both groups; however, patients performed more poorly than controls on the primary (working) memory aspect of the task. Regions showing rCBF changes overlapped in both groups and were similar to those seen in previous studies of normals; however, patients had smaller increases in rCBF than controls in frontal and superior temporal cortical regions bilaterally. Our results suggest that remitted patients with schizophrenia demonstrate impairments of capacity-limited information processing, which may be related to metabolic dysfunction within a distributed network of brain structures, including the prefrontal and temporal cortical regions; however, dysfunction limited to the frontal cortex cannot be ruled out by the results of this experiment.

Adult↗
PubMed1996

Association study of schizophrenia and the dopamine D3 receptor gene locus in two independent samples.

Using a case-control design, an association of schizophrenia with the dopamine D3 receptor gene (D3RG) locus was investigated. Initial analysis of pooled results from published studies revealed a significant excess of individuals homozygous for either allele among the patients. The association was next tested in two cohorts ascertained independently at Pittsburgh, Pennsylvania and at Houston, Texas. The Pittsburgh sample was comprised of patients with schizophrenia (DSM-III-R) (n = 130). The controls belonged to two groups: adults screened for the absence of substance abuse or major psychiatric illness (n = 128), and neonates (n = 160). Multivariate analysis suggested an association with allele 1 of the biallelic D3RG polymorphism in comparison with the adult, but not the neonatal, controls. The association was most marked among Caucasian patients with a family history of schizophrenia (odds ratio 13.69, confidence intervals 1.80, 104.30). Survival analysis suggested an earlier age of onset among male patients homozygous for allele 2. The Houston cohort included Caucasian patients with schizophrenia or schizoaffective disorder (DSM-III-R criteria, n = 50), and normal controls matched for gender (n = 51). In this group, no significant associations were noted among all the patients or among subgroups of patients based on family history or age of onset. Possible reasons for the discordant results are discussed.

Adult↗
PubMed1991

Electroencephalographic sleep and cerebral morphology in functional psychoses: a preliminary study with computed tomography.

We investigated the association between cerebral morphology as revealed by computed tomography and sleep polysomnographic findings in patients with functional psychoses. The third ventricle-brain ratios, caudate ratios, and anterior horn ratios were significantly negatively associated with sleep maintenance and were positively correlated with rapid eye movement (REM) latency. When the effects of illness severity were covaried out, the relation between REM latency and anterior horn ratios remained significant. Disturbances in sleep in some patients with schizophrenia and schizoaffective disorders may be related to dysfunction of forebrain structures, and may be similar to those seen in dementia.

Adult↗