THE FUNCTIONAL EMERGENCE OF PREFRONTALLY-GUIDED WORKING-MEMORY SYSTEMS IN 4-YEAR-OLD TO 8-YEAR-OLD CHILDREN

The neural processes that underlie the functional emergence of human c ognitive functions, particularly those associated with the prefrontal cortex (PFC), are of growing interest to developmental psychologists a nd neuroscientists. Specifically, working memory functions have been c orrelated with PFC activity in nonhuman primates and adult humans but have not been extensively studied in children. We examined the develop mental emergence of functions involved in working memory through the u se of the Cambridge Neuropsychological Test Automated Battery (CANTAB) , a computerized battery of nonverbal visually-presented neuropsycholo gical tests designed to dissociate frontal from temporal lobe behavior al functions. Participants were normal children, aged 4-8 (n = 181) an d a small group of young adults (n = 24) who completed measures of Spa tial Memory Span, Spatial Working Memory, the Tower of London planning task, Visual Pattern and Spatial Recognition tasks, and a Set-Shiftin g task. Findings indicate a general age-related progression in ability levels on frontal lobe tasks, with 4-year-olds performing worse than 5- to 7-year-olds on all measures. Eight-year-olds are superior to you nger children in their ability to solve complex problems but have not yet reached adult levels of performance on the most difficult items of the Tower of London and Spatial Working Memory tasks. We conclude tha t the development of working memory functions proceeds dimensionally, starting with refinement of basic perceptual and sensorimotor function s and culminating with the physiological maturation of widespread neur al networks that integrate complex processing demands inherent to work ing memory tasks. (C) 1998 Elsevier Science Ltd. All rights reserved.