MENTAL RETARDATION AND DEVELOPMENTAL DISABILITIES RESEARCH REVIEWS zyxwvutsrq 2: zyxwvutsrq 702-708 (7996) zyxwvutsr A zyxw NEUROPSYCHOLOGICAL PROFILE OF DOWN SYNDROME: COGNITIVE SKILLS AND BRAIN MORPHOLOGY Paul P. Wang Department of Pediatrics, University of Pennsylvania School of Medicine and Children’s Seashore House, Philadelphia, Pennsylvania zyxwv In children and young adults with Down syndrome, there exists a profile of neuropsychological strengths and weaknesses. Verbal short-term memory skills are diminished relative t o subjects with mental retardation resulting from other etiologies. On the other hand, visual-motor skills are comparatively well preserved. This profile distinguishes the population having Down syndrome from other impaired populations, although it may be confounded by dementia in later adult years. Down syndrome also results in a characteristic profile of brain morphology. In vivo magnetic resonance imaging studies have shown that the frontal and temporal regions of the brain are proportionally diminished in Down syndrome, but that the volumes of the subcortical nuclei are similar t o those in control subjects. This profile of brain morphology appears to correspond to both the neuropathologic data on Down syndrome and to the profile of cognitive skills in individuals who have this syndrome. Impairment of fundamental cognitive processes such as phonologic short-term memory is likely t o have implications with regard t o higher-order psychological and academic processes. Effective educational intervention must take such impairments into account during the development of individualized educational plans. Q 1996 Wiley-Liss, Inc. MRDD Research Reviews 2: 102-108 ~ ~~~~ ~~~~ Key Words: Down syndrome, neuropsychology, memory, visual- motor skills, brain morphology he bio-psychological study of Down syndrome can be said to date from the time of its namesake description. T Down’s report (1866) “Observation on an ethnic classification of idiots,” was an earnest, though grossly wrong and racist attempt to relate biology to cognition. Fortunately, Down syndrome has become the subject of recent psychological research that is theoretically and methodologically much more sophisticated than Down’s musings. Contemporary research on Down syndrome is motivated by multiple factors, including the educational care of people who have the disorder, exploration of the neurologic bases of cognition, and various theoretical considerations from develop- mental psychology. Mervis and her colleagues (Mervis, 1990), for instance, have provided some of the most elegant explications of language development in Down syndrome, demonstrating universal principles of language acquisition that also apply to the typically developing population. (Language development in Down syndrome is reviewed more generally in this issue by zyxwvu o 1996 Wiley-Liss, Inc. Kumin.) The recent compilations by Nadel (1988) and by Cicchetti and Beeghly (1990) illustrate some of the other productive avenues of investigation that Down syndrome has provided to developmental psychology. In contrast to these developmental psychological investiga- tions of Down syndrome, which focus closely on single aspects of cognition such as vocabulary acquisition or learning to count, there also has been a long line of neuropsychological studies of this syndrome. These studies have examined a broad array of cognitive skills, each of which is hypothesized to have a distinct brain basis. I will review these studies and the companion investigations of in vivo brain morphology in Down syndrome. AGE EFFECTS O N COGNITION The earliest neuropsychological studies of Down syn- drome were concerned with the effects of age on general intellectual ability (reviewed by Hartley, 1986). A large number of these studies found age-related decreases in the IQ of subjects with this disorder. However, the ability to generalize these results to current times is greatly limited by the fact that children with Down syndrome now are much more likely to be raised in stimulating home environments and to have challenging educational opportunities. Even the early research found that these variables are important predictors of cognitive ability in these children. Furthermore, it is clear that regardless of the course of their IQ scores, people with Down syndrome continue to advance in mental age and to acquire new cognitive skills, even through the third and fourth decades of their lives (Berry et al., 1984). A plethora of studies have been undertaken to investigate the effects of advanced age on cognitive ability in Down syndrome. As Wisniewslu reviews in greater detail in this issue, adults with Down syndrome all begin to show the neuropatho- logic hallmarks of Alzheimer’s disease after the age of 40 years, with many showing such stigmata by the age 35 years. Many of these older adults also develop clinical symptoms of dementia. Careful neuropsychological scrutiny suggests that even those without clinically diagnosed dementia may have mild impair- ments of long-term memory, which often is the only sign of Address corrcspondence to Dr Paul P. Wang, Children’s Seashore House, 3405 Civic Center Boulevard, Philadelphia, PA 19104-4388.