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Biomedical subjects

C M Yee

Publications and source records attributed to C M Yee.

4 recordsLinked to original sources

Early stimulus processing in dysthymia and anhedonia.

Previous event-related brain potential (ERP) research has found that dysthymic subjects differ from control subjects during later stages of information processing. An important issue that emerges from this literature is whether differences found in these ERP components, typically associated with cognitive processing, can be attributed to earlier differences in basic perceptual processing. This study was undertaken to determine whether early processing deficits are apparent in dysthymic persons. Responses of dysthymics (n = 23) were compared with those of anhedonic (n = 15) and normal control (n = 17) subjects. ERPs were recorded while subjects heard tones at 55, 65, 75, 85, and 95 dB. Overall, N1-P1 and N1-P2 components of the ERP increased in a strong linear fashion as stimulus intensity increased. Dysthymics did exhibit a smaller N1-P2 response than normal subjects, which suggests the presence of difficulties in initial perceptual processing.

Adult

Developmental Processes in Schizophrenic Disorders: longitudinal studies of vulnerability and stress.

The Developmental Processes in Schizophrenic Disorders project is a longitudinal study of schizophrenic patients who have recently had a first episode of psychosis. The project focuses on discriminating characteristics of schizophrenic patients that are "stable vulnerability indicators," "mediating vulnerability factors," and "episode indicators" by comparing normal subjects to schizophrenic patients assessed in clinically remitted and psychotic states. A parallel project goal is to identify predictors of relapse, social and work impairment, and illness course among potential psychobiological vulnerability factors and environmental potentiating factors. Hypothesized vulnerability factors and potential environmental stressors are examined first under standardized maintenance antipsychotic medication conditions for at least 1 year. Patients showing stable remission of psychosis after 1 year of maintenance antipsychotic medication are invited to enter drug crossover and withdrawal protocols to determine the need for continuous antipsychotic medication. Vulnerability and stress factors are again assessed. A summary of results to date is presented. Deficits in early components of processing visual arrays and in sustained discrimination of successive ambiguous perceptual inputs are relatively stable across psychotic and clinically remitted states in the schizophrenic patients. Performance on a vigilance task demanding active, working memory also remains abnormal during clinical remission but covaries significantly with psychotic state and is a candidate for a mediating vulnerability factor. Autonomic activation level does not appear to be an enduring vulnerability factor, but it predicts the extent of short-term symptomatic recovery and may mediate the impact of stressors. Under conditions of standardized, injectable antipsychotic medication, independent stressful life events and highly critical attitudes toward the patient in the social environment predict relapse risk. Prospective data suggest that signs and symptoms prodromal to psychotic relapse may be present in about 60 percent of patients.

Adolescent