The prefrontal cortex has been implicated in the mediation of executive processes that facilitate learning and memory. The authors hypothesized that children with prefrontal dysfunction related to phenylketonuria (PKU) would experience deficits in learning and memory because of impaired strategy use. They evaluated 23 children with PKU and 23 controls by using the California Verbal Learning Test-Children's Version (CVLT-C). General executive abilities were tested using the Stroop Color and Word Test, the Wisconsin Card Sorting Test, and phonemic and category fluency. Children with PKU, especially older children, showed poorer learning across trials and less use of semantic clustering on the CVLT-C but intact retention of previously encoded information. With the exception of phonemic fluency, deficits were not observed in general executive control. Results are discussed within the context of abnormalities in the prefrontal cortex and white matter of the brain.

Findings from previous research suggest that inhibitory control improves during early childhood and declines during late adulthood. Very few researchers, however, have examined life-span changes in this ability in single studies. Within this life-span context, we investigated 1 type of inhibitory control--the ability to inhibit aprepotent response and generate an incompatible response--in individuals ranging from 6 to 82 years of age. Examination of raw reaction time data revealed a significantly larger inhibitory control effect for children and older adults than for young adults. Using proportional and z score transformations, we demonstrated that a processing speed explanation is sufficient to account for the differences in performance between children and young adults; this explanation, however, did not adequately explain the discrepancy between young and older adults. Taken together, these findings suggest that, above and beyond differences in processing speed, inhibitory control was less efficient in older adults. Our findings are consistent with the assertion that inhibitory control develops quite early and declines at the later end of the developmental spectrum.

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. (JINS, 2002,8, 1–11.)

Findings from previous research suggest that inhibitory control improves during early childhood and declines during late adulthood. Very few researchers, however, have examined life-span changes in this ability in single studies. Within this life-span context, we investigated 1 type of inhibitory control--the ability to inhibit aprepotent response and generate an incompatible response--in individuals ranging from 6 to 82 years of age. Examination of raw reaction time data revealed a significantly larger inhibitory control effect for children and older adults than for young adults. Using proportional and z score transformations, we demonstrated that a processing speed explanation is sufficient to account for the differences in performance between children and young adults; this explanation, however, did not adequately explain the discrepancy between young and older adults. Taken together, these findings suggest that, above and beyond differences in processing speed, inhibitory control was less efficient in older adults. Our findings are consistent with the assertion that inhibitory control develops quite early and declines at the later end of the developmental spectrum.

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 De-mentia 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 (PϽ.05) correlations were modest (Յ0.21). Conclusion: Depression does not worsen cognitive test performance beyond the effect of dementia.