Absence of effect of depression on cognitive performance in early-stage Alzheimer disease.

BACKGROUND: Depression can interfere with the normal expression of cognitive abilities in adults of all ages, but it is unclear if depression in demented people, which is common, is associated with reduced cognitive performance beyond the effect of the dementia itself. OBJECTIVE: To determine if depression adds to the cognitive deficit in dementia. DESIGN: Performance on psychometric tests of memory and other cognitive function was correlated with the number of depressive features reported by the individual and by a knowledgeable collateral source, as well as the judgment of a research clinician as to whether the person was depressed. SETTING: An Alzheimer disease research center. PARTICIPANTS: The convenience sample included individuals with very mild (Clinical Dementia Rating, 0.5; n = 167 [mean age, 76.03 years]) or mild (Clinical Dementia Rating, 1; n = 155 [mean age, 78.41 years]) Alzheimer disease who were enrolled in ongoing longitudinal studies at the center. MAIN OUTCOME MEASURES: Psychometric measures of memory and cognition. RESULTS: Depression was present in 15% of the very mild and 24% of the mild dementia groups. There was no relation between the clinicians' diagnoses of depression and psychometric scores. Little relation was found between performance on the cognitive tests and the number of depressive features (maximum, 9) reported by the individual or collateral source. The few statistically significant (P<.05) correlations were modest (< or =0.21). CONCLUSION: Depression does not worsen cognitive test performance beyond the effect of dementia.

Age-related working memory impairments in children with prefrontal dysfunction associated with phenylketonuria.

The prefrontal cortex of the brain has been shown to play a crucial role in working memory, and age-related changes in prefrontal function may contribute to the improvements in working memory that are observed during childhood. We examined the developmental trajectory of working memory in school-age children with early-treated phenylketonuria (PKU), a metabolic disorder that results in prefrontal dysfunction. Using a recognition procedure, we evaluated working memory for letters, abstract objects, and spatial locations in 20 children with PKU and 20 typically developing control children. Children in both groups ranged from 6 to 17 years of age. Our findings revealed poorer performance across all three types of materials for children with PKU. In addition, there was a significant difference in the developmental trajectory of working memory for children with PKU as compared with controls. Specifically, deficits were not apparent in younger children with PKU. Instead, deficits were observed only in older children, suggesting the presence of a developmental deficit rather than a developmental delay in the working memory of children with PKU.